2017-05-21 19:50:59 -04:00
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use std::fmt;
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Big API incompatible error change, remove dependency on error_chain
The current situation with error_chain is less than ideal, and there are lots of
conflicting interests that are impossible to meet at once. Here is an
unorganized brain dump of the current situation, stay awhile and listen!
This change was triggered ultimately by the desire to make LuaError implement
Clone, and this is currently impossible with error_chain. LuaError must
implement Clone to be a proper lua citizen that can live as userdata within a
lua runtime, because there is no way to limit what the lua runtime can do with a
received error. Currently, this is solved by there being a rule that the error
will "expire" if the error is passed back into rust, and this is very
sub-optimal. In fact, one could easily imagine a scenario where lua is for
example memoizing some function, and if the function has ever errored in the
past the function should continue returning the same error, and this situation
immediately fails with this restriciton in place.
Additionally, there are other more minor problems with error_chain which make
the API less good than it could be, or limit how we can use error_chain. This
change has already solved a small bug in a Chucklefish project, where the
conversion from an external error type (Borrow[Mut]Error) was allowed but not
intended for user code, and was accidentally used. Additionally, pattern
matching on error_chain errors, which should be common when dealing with Lua, is
less convenient than a hand rolled error type.
So, if we decide not to use error_chain, we now have a new set of problems if we
decide interoperability with error_chain is important. The first problem we run
into is that there are two natural bounds for wrapped errors that we would
pick, (Error + Send + Sync), or just Error, and neither of them will
interoperate well with error_chain. (Error + Send + Sync) means we can't wrap
error chain errors into LuaError::ExternalError (they're missing the Sync
bound), and having the bounds be just Error means the opposite, that we can't
hold a LuaError inside an error_chain error.
We could just decide that interoperability with error_chain is the most
important qualification, and pick (Error + Send), but this causes a DIFFERENT
set of problems. The rust ecosystem has the two primary error bounds as Error
or (Error + Send + Sync), and there are Into impls from &str / String to
Box<Error + Send + Sync> for example, but NOT (Error + Send). This means that
we are forced to manually recreate the conversions from &str / String to
LuaError rather than relying on a single Into<Box<Error + Send + Sync>> bound,
but this means that string conversions have a different set of methods than
other error types for external error conversion. I have not been able to figure
out an API that I am happy with that uses the (Error + Send) bound. Box<Error>
is obnoxious because not having errors implement Send causes needless problems
in a multithreaded context, so that leaves (Error + Send + Sync). This is
actually a completely reasonable bound for external errors, and has the nice
String Into impls that we would want, the ONLY problem is that it is a pain to
interoperate with the current version of error_chain.
It would be nice to be able to specify the traits that an error generated by the
error_chain macro would implement, and this is apparently in progress in the
error_chain library. This would solve both the problem with not being able to
implement Clone and the problems with (Error + Send) bounds. I am not convinced
that this library should go back to using error_chain when that functionality is
in stable error_chain though, because of the other minor usability problems with
using error_chain.
In that theoretical situation, the downside of NOT using error_chain is simply
that there would not be automatic stacktraces of LuaError. This is not a huge
problem, because stack traces of lua errors are not extremely useful, and for
external errors it is not too hard to create a different version of the
LuaExternalResult / LuaExternalError traits and do conversion from an
error_chain type into a type that will print the stacktrace on display, or
use downcasting in the error causes.
So in summary, this library is no longer using error_chain, and probably will
not use it again in the future. Currently this means that to interoperate with
error_chain, you should use error_chain 0.8.1, which derives Sync on errors, or
wait for a version that supports user defined trait derives. In the future
when error_chain supports user defined trait derives, users may have to take an
extra step to make wrapped external errors print the stacktrace that they
capture.
This change works, but is not entirely complete. There is no error
documentation yet, and the change brought to a head an ugly module organization
problem. There will be more commits for documentation and reorganization, then
a new stable version of rlua.
2017-06-24 18:11:56 -04:00
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use std::sync::Arc;
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2017-07-24 07:30:29 -04:00
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use std::error::Error as StdError;
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use std::result::Result as StdResult;
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2017-06-24 20:57:04 -04:00
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#[derive(Debug, Clone)]
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2017-07-18 16:21:12 -04:00
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pub enum Error {
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2017-06-27 14:05:49 -04:00
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/// Lua syntax error, aka `LUA_ERRSYNTAX` that is NOT an incomplete statement.
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2017-06-25 04:25:48 -04:00
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SyntaxError(String),
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2017-06-27 14:05:49 -04:00
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/// Lua syntax error that IS an incomplete statement. Useful for implementing a REPL.
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2017-06-25 04:25:48 -04:00
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IncompleteStatement(String),
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/// Lua runtime error, aka `LUA_ERRRUN`.
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2017-06-24 20:57:04 -04:00
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RuntimeError(String),
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2017-06-25 04:25:48 -04:00
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/// Lua error from inside an error handler, aka `LUA_ERRERR`.
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2017-06-24 20:57:04 -04:00
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ErrorError(String),
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2017-06-25 04:25:48 -04:00
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/// A generic Rust -> Lua conversion error.
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ToLuaConversionError(String),
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/// A generic Lua -> Rust conversion error.
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FromLuaConversionError(String),
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2017-07-18 16:21:12 -04:00
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/// A `Thread` was resumed and the coroutine was no longer active.
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2017-06-24 20:57:04 -04:00
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CoroutineInactive,
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2017-07-23 06:29:02 -04:00
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/// An `AnyUserData` is not the expected type in a borrow.
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2017-06-25 04:25:48 -04:00
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UserDataTypeMismatch,
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2017-07-23 06:29:02 -04:00
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/// An `AnyUserData` immutable borrow failed because it is already borrowed mutably.
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2017-06-25 04:25:48 -04:00
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UserDataBorrowError,
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2017-07-23 06:29:02 -04:00
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/// An `AnyUserData` mutable borrow failed because it is already borrowed.
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2017-06-25 04:25:48 -04:00
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UserDataBorrowMutError,
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2017-07-18 16:21:12 -04:00
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/// Lua error that originated as a Error in a callback. The first field is the lua error as
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/// a string, the second field is the Arc holding the original Error.
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CallbackError(String, Arc<Error>),
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2017-06-27 14:05:49 -04:00
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/// Any custom external error type, mostly useful for returning external error types from
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/// callbacks.
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2017-07-24 07:30:29 -04:00
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ExternalError(Arc<StdError + Send + Sync>),
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Big API incompatible error change, remove dependency on error_chain
The current situation with error_chain is less than ideal, and there are lots of
conflicting interests that are impossible to meet at once. Here is an
unorganized brain dump of the current situation, stay awhile and listen!
This change was triggered ultimately by the desire to make LuaError implement
Clone, and this is currently impossible with error_chain. LuaError must
implement Clone to be a proper lua citizen that can live as userdata within a
lua runtime, because there is no way to limit what the lua runtime can do with a
received error. Currently, this is solved by there being a rule that the error
will "expire" if the error is passed back into rust, and this is very
sub-optimal. In fact, one could easily imagine a scenario where lua is for
example memoizing some function, and if the function has ever errored in the
past the function should continue returning the same error, and this situation
immediately fails with this restriciton in place.
Additionally, there are other more minor problems with error_chain which make
the API less good than it could be, or limit how we can use error_chain. This
change has already solved a small bug in a Chucklefish project, where the
conversion from an external error type (Borrow[Mut]Error) was allowed but not
intended for user code, and was accidentally used. Additionally, pattern
matching on error_chain errors, which should be common when dealing with Lua, is
less convenient than a hand rolled error type.
So, if we decide not to use error_chain, we now have a new set of problems if we
decide interoperability with error_chain is important. The first problem we run
into is that there are two natural bounds for wrapped errors that we would
pick, (Error + Send + Sync), or just Error, and neither of them will
interoperate well with error_chain. (Error + Send + Sync) means we can't wrap
error chain errors into LuaError::ExternalError (they're missing the Sync
bound), and having the bounds be just Error means the opposite, that we can't
hold a LuaError inside an error_chain error.
We could just decide that interoperability with error_chain is the most
important qualification, and pick (Error + Send), but this causes a DIFFERENT
set of problems. The rust ecosystem has the two primary error bounds as Error
or (Error + Send + Sync), and there are Into impls from &str / String to
Box<Error + Send + Sync> for example, but NOT (Error + Send). This means that
we are forced to manually recreate the conversions from &str / String to
LuaError rather than relying on a single Into<Box<Error + Send + Sync>> bound,
but this means that string conversions have a different set of methods than
other error types for external error conversion. I have not been able to figure
out an API that I am happy with that uses the (Error + Send) bound. Box<Error>
is obnoxious because not having errors implement Send causes needless problems
in a multithreaded context, so that leaves (Error + Send + Sync). This is
actually a completely reasonable bound for external errors, and has the nice
String Into impls that we would want, the ONLY problem is that it is a pain to
interoperate with the current version of error_chain.
It would be nice to be able to specify the traits that an error generated by the
error_chain macro would implement, and this is apparently in progress in the
error_chain library. This would solve both the problem with not being able to
implement Clone and the problems with (Error + Send) bounds. I am not convinced
that this library should go back to using error_chain when that functionality is
in stable error_chain though, because of the other minor usability problems with
using error_chain.
In that theoretical situation, the downside of NOT using error_chain is simply
that there would not be automatic stacktraces of LuaError. This is not a huge
problem, because stack traces of lua errors are not extremely useful, and for
external errors it is not too hard to create a different version of the
LuaExternalResult / LuaExternalError traits and do conversion from an
error_chain type into a type that will print the stacktrace on display, or
use downcasting in the error causes.
So in summary, this library is no longer using error_chain, and probably will
not use it again in the future. Currently this means that to interoperate with
error_chain, you should use error_chain 0.8.1, which derives Sync on errors, or
wait for a version that supports user defined trait derives. In the future
when error_chain supports user defined trait derives, users may have to take an
extra step to make wrapped external errors print the stacktrace that they
capture.
This change works, but is not entirely complete. There is no error
documentation yet, and the change brought to a head an ugly module organization
problem. There will be more commits for documentation and reorganization, then
a new stable version of rlua.
2017-06-24 18:11:56 -04:00
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}
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2017-07-24 07:30:29 -04:00
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pub type Result<T> = StdResult<T, Error>;
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2017-05-21 19:50:59 -04:00
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2017-07-18 16:21:12 -04:00
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impl fmt::Display for Error {
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fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
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match *self {
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Error::SyntaxError(ref msg) => write!(fmt, "Lua syntax error: {}", msg),
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Error::IncompleteStatement(ref msg) => {
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2017-06-25 04:25:48 -04:00
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write!(fmt, "Lua syntax error (incomplete statement): {}", msg)
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2017-06-24 20:57:04 -04:00
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}
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2017-07-18 16:21:12 -04:00
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Error::RuntimeError(ref msg) => write!(fmt, "Lua runtime error: {}", msg),
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Error::ErrorError(ref msg) => write!(fmt, "Lua error in error handler: {}", msg),
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Error::ToLuaConversionError(ref msg) => {
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2017-06-24 20:57:04 -04:00
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write!(fmt, "Error converting rust type to lua: {}", msg)
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}
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2017-07-18 16:21:12 -04:00
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Error::FromLuaConversionError(ref msg) => {
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2017-06-24 20:57:04 -04:00
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write!(fmt, "Error converting lua type to rust: {}", msg)
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}
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2017-07-18 16:21:12 -04:00
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Error::CoroutineInactive => write!(fmt, "Cannot resume inactive coroutine"),
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Error::UserDataTypeMismatch => write!(fmt, "Userdata not expected type"),
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Error::UserDataBorrowError => write!(fmt, "Userdata already mutably borrowed"),
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Error::UserDataBorrowMutError => write!(fmt, "Userdata already borrowed"),
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2017-07-24 10:40:00 -04:00
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Error::CallbackError(ref msg, _) => write!(fmt, "Error during lua callback: {}", msg),
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2017-07-18 16:21:12 -04:00
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Error::ExternalError(ref err) => err.fmt(fmt),
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Big API incompatible error change, remove dependency on error_chain
The current situation with error_chain is less than ideal, and there are lots of
conflicting interests that are impossible to meet at once. Here is an
unorganized brain dump of the current situation, stay awhile and listen!
This change was triggered ultimately by the desire to make LuaError implement
Clone, and this is currently impossible with error_chain. LuaError must
implement Clone to be a proper lua citizen that can live as userdata within a
lua runtime, because there is no way to limit what the lua runtime can do with a
received error. Currently, this is solved by there being a rule that the error
will "expire" if the error is passed back into rust, and this is very
sub-optimal. In fact, one could easily imagine a scenario where lua is for
example memoizing some function, and if the function has ever errored in the
past the function should continue returning the same error, and this situation
immediately fails with this restriciton in place.
Additionally, there are other more minor problems with error_chain which make
the API less good than it could be, or limit how we can use error_chain. This
change has already solved a small bug in a Chucklefish project, where the
conversion from an external error type (Borrow[Mut]Error) was allowed but not
intended for user code, and was accidentally used. Additionally, pattern
matching on error_chain errors, which should be common when dealing with Lua, is
less convenient than a hand rolled error type.
So, if we decide not to use error_chain, we now have a new set of problems if we
decide interoperability with error_chain is important. The first problem we run
into is that there are two natural bounds for wrapped errors that we would
pick, (Error + Send + Sync), or just Error, and neither of them will
interoperate well with error_chain. (Error + Send + Sync) means we can't wrap
error chain errors into LuaError::ExternalError (they're missing the Sync
bound), and having the bounds be just Error means the opposite, that we can't
hold a LuaError inside an error_chain error.
We could just decide that interoperability with error_chain is the most
important qualification, and pick (Error + Send), but this causes a DIFFERENT
set of problems. The rust ecosystem has the two primary error bounds as Error
or (Error + Send + Sync), and there are Into impls from &str / String to
Box<Error + Send + Sync> for example, but NOT (Error + Send). This means that
we are forced to manually recreate the conversions from &str / String to
LuaError rather than relying on a single Into<Box<Error + Send + Sync>> bound,
but this means that string conversions have a different set of methods than
other error types for external error conversion. I have not been able to figure
out an API that I am happy with that uses the (Error + Send) bound. Box<Error>
is obnoxious because not having errors implement Send causes needless problems
in a multithreaded context, so that leaves (Error + Send + Sync). This is
actually a completely reasonable bound for external errors, and has the nice
String Into impls that we would want, the ONLY problem is that it is a pain to
interoperate with the current version of error_chain.
It would be nice to be able to specify the traits that an error generated by the
error_chain macro would implement, and this is apparently in progress in the
error_chain library. This would solve both the problem with not being able to
implement Clone and the problems with (Error + Send) bounds. I am not convinced
that this library should go back to using error_chain when that functionality is
in stable error_chain though, because of the other minor usability problems with
using error_chain.
In that theoretical situation, the downside of NOT using error_chain is simply
that there would not be automatic stacktraces of LuaError. This is not a huge
problem, because stack traces of lua errors are not extremely useful, and for
external errors it is not too hard to create a different version of the
LuaExternalResult / LuaExternalError traits and do conversion from an
error_chain type into a type that will print the stacktrace on display, or
use downcasting in the error causes.
So in summary, this library is no longer using error_chain, and probably will
not use it again in the future. Currently this means that to interoperate with
error_chain, you should use error_chain 0.8.1, which derives Sync on errors, or
wait for a version that supports user defined trait derives. In the future
when error_chain supports user defined trait derives, users may have to take an
extra step to make wrapped external errors print the stacktrace that they
capture.
This change works, but is not entirely complete. There is no error
documentation yet, and the change brought to a head an ugly module organization
problem. There will be more commits for documentation and reorganization, then
a new stable version of rlua.
2017-06-24 18:11:56 -04:00
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}
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2017-05-21 19:50:59 -04:00
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}
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}
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2017-07-24 07:30:29 -04:00
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impl StdError for Error {
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2017-05-21 19:50:59 -04:00
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fn description(&self) -> &str {
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2017-07-18 16:21:12 -04:00
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match *self {
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Error::SyntaxError(_) => "lua syntax error",
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Error::IncompleteStatement(_) => "lua incomplete statement",
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Error::RuntimeError(_) => "lua runtime error",
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Error::ErrorError(_) => "lua error handling error",
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Error::ToLuaConversionError(_) => "conversion error to lua",
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Error::FromLuaConversionError(_) => "conversion error from lua",
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Error::CoroutineInactive => "lua coroutine inactive",
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Error::UserDataTypeMismatch => "lua userdata type mismatch",
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Error::UserDataBorrowError => "lua userdata already mutably borrowed",
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Error::UserDataBorrowMutError => "lua userdata already borrowed",
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Error::CallbackError(_, _) => "lua callback error",
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Error::ExternalError(ref err) => err.description(),
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Big API incompatible error change, remove dependency on error_chain
The current situation with error_chain is less than ideal, and there are lots of
conflicting interests that are impossible to meet at once. Here is an
unorganized brain dump of the current situation, stay awhile and listen!
This change was triggered ultimately by the desire to make LuaError implement
Clone, and this is currently impossible with error_chain. LuaError must
implement Clone to be a proper lua citizen that can live as userdata within a
lua runtime, because there is no way to limit what the lua runtime can do with a
received error. Currently, this is solved by there being a rule that the error
will "expire" if the error is passed back into rust, and this is very
sub-optimal. In fact, one could easily imagine a scenario where lua is for
example memoizing some function, and if the function has ever errored in the
past the function should continue returning the same error, and this situation
immediately fails with this restriciton in place.
Additionally, there are other more minor problems with error_chain which make
the API less good than it could be, or limit how we can use error_chain. This
change has already solved a small bug in a Chucklefish project, where the
conversion from an external error type (Borrow[Mut]Error) was allowed but not
intended for user code, and was accidentally used. Additionally, pattern
matching on error_chain errors, which should be common when dealing with Lua, is
less convenient than a hand rolled error type.
So, if we decide not to use error_chain, we now have a new set of problems if we
decide interoperability with error_chain is important. The first problem we run
into is that there are two natural bounds for wrapped errors that we would
pick, (Error + Send + Sync), or just Error, and neither of them will
interoperate well with error_chain. (Error + Send + Sync) means we can't wrap
error chain errors into LuaError::ExternalError (they're missing the Sync
bound), and having the bounds be just Error means the opposite, that we can't
hold a LuaError inside an error_chain error.
We could just decide that interoperability with error_chain is the most
important qualification, and pick (Error + Send), but this causes a DIFFERENT
set of problems. The rust ecosystem has the two primary error bounds as Error
or (Error + Send + Sync), and there are Into impls from &str / String to
Box<Error + Send + Sync> for example, but NOT (Error + Send). This means that
we are forced to manually recreate the conversions from &str / String to
LuaError rather than relying on a single Into<Box<Error + Send + Sync>> bound,
but this means that string conversions have a different set of methods than
other error types for external error conversion. I have not been able to figure
out an API that I am happy with that uses the (Error + Send) bound. Box<Error>
is obnoxious because not having errors implement Send causes needless problems
in a multithreaded context, so that leaves (Error + Send + Sync). This is
actually a completely reasonable bound for external errors, and has the nice
String Into impls that we would want, the ONLY problem is that it is a pain to
interoperate with the current version of error_chain.
It would be nice to be able to specify the traits that an error generated by the
error_chain macro would implement, and this is apparently in progress in the
error_chain library. This would solve both the problem with not being able to
implement Clone and the problems with (Error + Send) bounds. I am not convinced
that this library should go back to using error_chain when that functionality is
in stable error_chain though, because of the other minor usability problems with
using error_chain.
In that theoretical situation, the downside of NOT using error_chain is simply
that there would not be automatic stacktraces of LuaError. This is not a huge
problem, because stack traces of lua errors are not extremely useful, and for
external errors it is not too hard to create a different version of the
LuaExternalResult / LuaExternalError traits and do conversion from an
error_chain type into a type that will print the stacktrace on display, or
use downcasting in the error causes.
So in summary, this library is no longer using error_chain, and probably will
not use it again in the future. Currently this means that to interoperate with
error_chain, you should use error_chain 0.8.1, which derives Sync on errors, or
wait for a version that supports user defined trait derives. In the future
when error_chain supports user defined trait derives, users may have to take an
extra step to make wrapped external errors print the stacktrace that they
capture.
This change works, but is not entirely complete. There is no error
documentation yet, and the change brought to a head an ugly module organization
problem. There will be more commits for documentation and reorganization, then
a new stable version of rlua.
2017-06-24 18:11:56 -04:00
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}
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2017-05-21 19:50:59 -04:00
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}
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2017-07-24 07:30:29 -04:00
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fn cause(&self) -> Option<&StdError> {
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2017-07-18 16:21:12 -04:00
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match *self {
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Error::CallbackError(_, ref cause) => Some(cause.as_ref()),
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Error::ExternalError(ref err) => err.cause(),
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Big API incompatible error change, remove dependency on error_chain
The current situation with error_chain is less than ideal, and there are lots of
conflicting interests that are impossible to meet at once. Here is an
unorganized brain dump of the current situation, stay awhile and listen!
This change was triggered ultimately by the desire to make LuaError implement
Clone, and this is currently impossible with error_chain. LuaError must
implement Clone to be a proper lua citizen that can live as userdata within a
lua runtime, because there is no way to limit what the lua runtime can do with a
received error. Currently, this is solved by there being a rule that the error
will "expire" if the error is passed back into rust, and this is very
sub-optimal. In fact, one could easily imagine a scenario where lua is for
example memoizing some function, and if the function has ever errored in the
past the function should continue returning the same error, and this situation
immediately fails with this restriciton in place.
Additionally, there are other more minor problems with error_chain which make
the API less good than it could be, or limit how we can use error_chain. This
change has already solved a small bug in a Chucklefish project, where the
conversion from an external error type (Borrow[Mut]Error) was allowed but not
intended for user code, and was accidentally used. Additionally, pattern
matching on error_chain errors, which should be common when dealing with Lua, is
less convenient than a hand rolled error type.
So, if we decide not to use error_chain, we now have a new set of problems if we
decide interoperability with error_chain is important. The first problem we run
into is that there are two natural bounds for wrapped errors that we would
pick, (Error + Send + Sync), or just Error, and neither of them will
interoperate well with error_chain. (Error + Send + Sync) means we can't wrap
error chain errors into LuaError::ExternalError (they're missing the Sync
bound), and having the bounds be just Error means the opposite, that we can't
hold a LuaError inside an error_chain error.
We could just decide that interoperability with error_chain is the most
important qualification, and pick (Error + Send), but this causes a DIFFERENT
set of problems. The rust ecosystem has the two primary error bounds as Error
or (Error + Send + Sync), and there are Into impls from &str / String to
Box<Error + Send + Sync> for example, but NOT (Error + Send). This means that
we are forced to manually recreate the conversions from &str / String to
LuaError rather than relying on a single Into<Box<Error + Send + Sync>> bound,
but this means that string conversions have a different set of methods than
other error types for external error conversion. I have not been able to figure
out an API that I am happy with that uses the (Error + Send) bound. Box<Error>
is obnoxious because not having errors implement Send causes needless problems
in a multithreaded context, so that leaves (Error + Send + Sync). This is
actually a completely reasonable bound for external errors, and has the nice
String Into impls that we would want, the ONLY problem is that it is a pain to
interoperate with the current version of error_chain.
It would be nice to be able to specify the traits that an error generated by the
error_chain macro would implement, and this is apparently in progress in the
error_chain library. This would solve both the problem with not being able to
implement Clone and the problems with (Error + Send) bounds. I am not convinced
that this library should go back to using error_chain when that functionality is
in stable error_chain though, because of the other minor usability problems with
using error_chain.
In that theoretical situation, the downside of NOT using error_chain is simply
that there would not be automatic stacktraces of LuaError. This is not a huge
problem, because stack traces of lua errors are not extremely useful, and for
external errors it is not too hard to create a different version of the
LuaExternalResult / LuaExternalError traits and do conversion from an
error_chain type into a type that will print the stacktrace on display, or
use downcasting in the error causes.
So in summary, this library is no longer using error_chain, and probably will
not use it again in the future. Currently this means that to interoperate with
error_chain, you should use error_chain 0.8.1, which derives Sync on errors, or
wait for a version that supports user defined trait derives. In the future
when error_chain supports user defined trait derives, users may have to take an
extra step to make wrapped external errors print the stacktrace that they
capture.
This change works, but is not entirely complete. There is no error
documentation yet, and the change brought to a head an ugly module organization
problem. There will be more commits for documentation and reorganization, then
a new stable version of rlua.
2017-06-24 18:11:56 -04:00
|
|
|
_ => None,
|
|
|
|
}
|
2017-05-21 19:50:59 -04:00
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2017-07-18 16:21:12 -04:00
|
|
|
impl Error {
|
2017-07-24 07:30:29 -04:00
|
|
|
pub fn external<T: 'static + StdError + Send + Sync>(err: T) -> Error {
|
2017-07-18 16:21:12 -04:00
|
|
|
Error::ExternalError(Arc::new(err))
|
2017-05-21 19:50:59 -04:00
|
|
|
}
|
Big API incompatible error change, remove dependency on error_chain
The current situation with error_chain is less than ideal, and there are lots of
conflicting interests that are impossible to meet at once. Here is an
unorganized brain dump of the current situation, stay awhile and listen!
This change was triggered ultimately by the desire to make LuaError implement
Clone, and this is currently impossible with error_chain. LuaError must
implement Clone to be a proper lua citizen that can live as userdata within a
lua runtime, because there is no way to limit what the lua runtime can do with a
received error. Currently, this is solved by there being a rule that the error
will "expire" if the error is passed back into rust, and this is very
sub-optimal. In fact, one could easily imagine a scenario where lua is for
example memoizing some function, and if the function has ever errored in the
past the function should continue returning the same error, and this situation
immediately fails with this restriciton in place.
Additionally, there are other more minor problems with error_chain which make
the API less good than it could be, or limit how we can use error_chain. This
change has already solved a small bug in a Chucklefish project, where the
conversion from an external error type (Borrow[Mut]Error) was allowed but not
intended for user code, and was accidentally used. Additionally, pattern
matching on error_chain errors, which should be common when dealing with Lua, is
less convenient than a hand rolled error type.
So, if we decide not to use error_chain, we now have a new set of problems if we
decide interoperability with error_chain is important. The first problem we run
into is that there are two natural bounds for wrapped errors that we would
pick, (Error + Send + Sync), or just Error, and neither of them will
interoperate well with error_chain. (Error + Send + Sync) means we can't wrap
error chain errors into LuaError::ExternalError (they're missing the Sync
bound), and having the bounds be just Error means the opposite, that we can't
hold a LuaError inside an error_chain error.
We could just decide that interoperability with error_chain is the most
important qualification, and pick (Error + Send), but this causes a DIFFERENT
set of problems. The rust ecosystem has the two primary error bounds as Error
or (Error + Send + Sync), and there are Into impls from &str / String to
Box<Error + Send + Sync> for example, but NOT (Error + Send). This means that
we are forced to manually recreate the conversions from &str / String to
LuaError rather than relying on a single Into<Box<Error + Send + Sync>> bound,
but this means that string conversions have a different set of methods than
other error types for external error conversion. I have not been able to figure
out an API that I am happy with that uses the (Error + Send) bound. Box<Error>
is obnoxious because not having errors implement Send causes needless problems
in a multithreaded context, so that leaves (Error + Send + Sync). This is
actually a completely reasonable bound for external errors, and has the nice
String Into impls that we would want, the ONLY problem is that it is a pain to
interoperate with the current version of error_chain.
It would be nice to be able to specify the traits that an error generated by the
error_chain macro would implement, and this is apparently in progress in the
error_chain library. This would solve both the problem with not being able to
implement Clone and the problems with (Error + Send) bounds. I am not convinced
that this library should go back to using error_chain when that functionality is
in stable error_chain though, because of the other minor usability problems with
using error_chain.
In that theoretical situation, the downside of NOT using error_chain is simply
that there would not be automatic stacktraces of LuaError. This is not a huge
problem, because stack traces of lua errors are not extremely useful, and for
external errors it is not too hard to create a different version of the
LuaExternalResult / LuaExternalError traits and do conversion from an
error_chain type into a type that will print the stacktrace on display, or
use downcasting in the error causes.
So in summary, this library is no longer using error_chain, and probably will
not use it again in the future. Currently this means that to interoperate with
error_chain, you should use error_chain 0.8.1, which derives Sync on errors, or
wait for a version that supports user defined trait derives. In the future
when error_chain supports user defined trait derives, users may have to take an
extra step to make wrapped external errors print the stacktrace that they
capture.
This change works, but is not entirely complete. There is no error
documentation yet, and the change brought to a head an ugly module organization
problem. There will be more commits for documentation and reorganization, then
a new stable version of rlua.
2017-06-24 18:11:56 -04:00
|
|
|
}
|
2017-05-21 19:50:59 -04:00
|
|
|
|
2017-07-24 07:12:52 -04:00
|
|
|
pub trait ExternalError {
|
2017-07-18 16:21:12 -04:00
|
|
|
fn to_lua_err(self) -> Error;
|
Big API incompatible error change, remove dependency on error_chain
The current situation with error_chain is less than ideal, and there are lots of
conflicting interests that are impossible to meet at once. Here is an
unorganized brain dump of the current situation, stay awhile and listen!
This change was triggered ultimately by the desire to make LuaError implement
Clone, and this is currently impossible with error_chain. LuaError must
implement Clone to be a proper lua citizen that can live as userdata within a
lua runtime, because there is no way to limit what the lua runtime can do with a
received error. Currently, this is solved by there being a rule that the error
will "expire" if the error is passed back into rust, and this is very
sub-optimal. In fact, one could easily imagine a scenario where lua is for
example memoizing some function, and if the function has ever errored in the
past the function should continue returning the same error, and this situation
immediately fails with this restriciton in place.
Additionally, there are other more minor problems with error_chain which make
the API less good than it could be, or limit how we can use error_chain. This
change has already solved a small bug in a Chucklefish project, where the
conversion from an external error type (Borrow[Mut]Error) was allowed but not
intended for user code, and was accidentally used. Additionally, pattern
matching on error_chain errors, which should be common when dealing with Lua, is
less convenient than a hand rolled error type.
So, if we decide not to use error_chain, we now have a new set of problems if we
decide interoperability with error_chain is important. The first problem we run
into is that there are two natural bounds for wrapped errors that we would
pick, (Error + Send + Sync), or just Error, and neither of them will
interoperate well with error_chain. (Error + Send + Sync) means we can't wrap
error chain errors into LuaError::ExternalError (they're missing the Sync
bound), and having the bounds be just Error means the opposite, that we can't
hold a LuaError inside an error_chain error.
We could just decide that interoperability with error_chain is the most
important qualification, and pick (Error + Send), but this causes a DIFFERENT
set of problems. The rust ecosystem has the two primary error bounds as Error
or (Error + Send + Sync), and there are Into impls from &str / String to
Box<Error + Send + Sync> for example, but NOT (Error + Send). This means that
we are forced to manually recreate the conversions from &str / String to
LuaError rather than relying on a single Into<Box<Error + Send + Sync>> bound,
but this means that string conversions have a different set of methods than
other error types for external error conversion. I have not been able to figure
out an API that I am happy with that uses the (Error + Send) bound. Box<Error>
is obnoxious because not having errors implement Send causes needless problems
in a multithreaded context, so that leaves (Error + Send + Sync). This is
actually a completely reasonable bound for external errors, and has the nice
String Into impls that we would want, the ONLY problem is that it is a pain to
interoperate with the current version of error_chain.
It would be nice to be able to specify the traits that an error generated by the
error_chain macro would implement, and this is apparently in progress in the
error_chain library. This would solve both the problem with not being able to
implement Clone and the problems with (Error + Send) bounds. I am not convinced
that this library should go back to using error_chain when that functionality is
in stable error_chain though, because of the other minor usability problems with
using error_chain.
In that theoretical situation, the downside of NOT using error_chain is simply
that there would not be automatic stacktraces of LuaError. This is not a huge
problem, because stack traces of lua errors are not extremely useful, and for
external errors it is not too hard to create a different version of the
LuaExternalResult / LuaExternalError traits and do conversion from an
error_chain type into a type that will print the stacktrace on display, or
use downcasting in the error causes.
So in summary, this library is no longer using error_chain, and probably will
not use it again in the future. Currently this means that to interoperate with
error_chain, you should use error_chain 0.8.1, which derives Sync on errors, or
wait for a version that supports user defined trait derives. In the future
when error_chain supports user defined trait derives, users may have to take an
extra step to make wrapped external errors print the stacktrace that they
capture.
This change works, but is not entirely complete. There is no error
documentation yet, and the change brought to a head an ugly module organization
problem. There will be more commits for documentation and reorganization, then
a new stable version of rlua.
2017-06-24 18:11:56 -04:00
|
|
|
}
|
|
|
|
|
2017-07-24 07:12:52 -04:00
|
|
|
impl<E> ExternalError for E
|
Big API incompatible error change, remove dependency on error_chain
The current situation with error_chain is less than ideal, and there are lots of
conflicting interests that are impossible to meet at once. Here is an
unorganized brain dump of the current situation, stay awhile and listen!
This change was triggered ultimately by the desire to make LuaError implement
Clone, and this is currently impossible with error_chain. LuaError must
implement Clone to be a proper lua citizen that can live as userdata within a
lua runtime, because there is no way to limit what the lua runtime can do with a
received error. Currently, this is solved by there being a rule that the error
will "expire" if the error is passed back into rust, and this is very
sub-optimal. In fact, one could easily imagine a scenario where lua is for
example memoizing some function, and if the function has ever errored in the
past the function should continue returning the same error, and this situation
immediately fails with this restriciton in place.
Additionally, there are other more minor problems with error_chain which make
the API less good than it could be, or limit how we can use error_chain. This
change has already solved a small bug in a Chucklefish project, where the
conversion from an external error type (Borrow[Mut]Error) was allowed but not
intended for user code, and was accidentally used. Additionally, pattern
matching on error_chain errors, which should be common when dealing with Lua, is
less convenient than a hand rolled error type.
So, if we decide not to use error_chain, we now have a new set of problems if we
decide interoperability with error_chain is important. The first problem we run
into is that there are two natural bounds for wrapped errors that we would
pick, (Error + Send + Sync), or just Error, and neither of them will
interoperate well with error_chain. (Error + Send + Sync) means we can't wrap
error chain errors into LuaError::ExternalError (they're missing the Sync
bound), and having the bounds be just Error means the opposite, that we can't
hold a LuaError inside an error_chain error.
We could just decide that interoperability with error_chain is the most
important qualification, and pick (Error + Send), but this causes a DIFFERENT
set of problems. The rust ecosystem has the two primary error bounds as Error
or (Error + Send + Sync), and there are Into impls from &str / String to
Box<Error + Send + Sync> for example, but NOT (Error + Send). This means that
we are forced to manually recreate the conversions from &str / String to
LuaError rather than relying on a single Into<Box<Error + Send + Sync>> bound,
but this means that string conversions have a different set of methods than
other error types for external error conversion. I have not been able to figure
out an API that I am happy with that uses the (Error + Send) bound. Box<Error>
is obnoxious because not having errors implement Send causes needless problems
in a multithreaded context, so that leaves (Error + Send + Sync). This is
actually a completely reasonable bound for external errors, and has the nice
String Into impls that we would want, the ONLY problem is that it is a pain to
interoperate with the current version of error_chain.
It would be nice to be able to specify the traits that an error generated by the
error_chain macro would implement, and this is apparently in progress in the
error_chain library. This would solve both the problem with not being able to
implement Clone and the problems with (Error + Send) bounds. I am not convinced
that this library should go back to using error_chain when that functionality is
in stable error_chain though, because of the other minor usability problems with
using error_chain.
In that theoretical situation, the downside of NOT using error_chain is simply
that there would not be automatic stacktraces of LuaError. This is not a huge
problem, because stack traces of lua errors are not extremely useful, and for
external errors it is not too hard to create a different version of the
LuaExternalResult / LuaExternalError traits and do conversion from an
error_chain type into a type that will print the stacktrace on display, or
use downcasting in the error causes.
So in summary, this library is no longer using error_chain, and probably will
not use it again in the future. Currently this means that to interoperate with
error_chain, you should use error_chain 0.8.1, which derives Sync on errors, or
wait for a version that supports user defined trait derives. In the future
when error_chain supports user defined trait derives, users may have to take an
extra step to make wrapped external errors print the stacktrace that they
capture.
This change works, but is not entirely complete. There is no error
documentation yet, and the change brought to a head an ugly module organization
problem. There will be more commits for documentation and reorganization, then
a new stable version of rlua.
2017-06-24 18:11:56 -04:00
|
|
|
where
|
2017-07-24 07:30:29 -04:00
|
|
|
E: Into<Box<StdError + Send + Sync>>,
|
Big API incompatible error change, remove dependency on error_chain
The current situation with error_chain is less than ideal, and there are lots of
conflicting interests that are impossible to meet at once. Here is an
unorganized brain dump of the current situation, stay awhile and listen!
This change was triggered ultimately by the desire to make LuaError implement
Clone, and this is currently impossible with error_chain. LuaError must
implement Clone to be a proper lua citizen that can live as userdata within a
lua runtime, because there is no way to limit what the lua runtime can do with a
received error. Currently, this is solved by there being a rule that the error
will "expire" if the error is passed back into rust, and this is very
sub-optimal. In fact, one could easily imagine a scenario where lua is for
example memoizing some function, and if the function has ever errored in the
past the function should continue returning the same error, and this situation
immediately fails with this restriciton in place.
Additionally, there are other more minor problems with error_chain which make
the API less good than it could be, or limit how we can use error_chain. This
change has already solved a small bug in a Chucklefish project, where the
conversion from an external error type (Borrow[Mut]Error) was allowed but not
intended for user code, and was accidentally used. Additionally, pattern
matching on error_chain errors, which should be common when dealing with Lua, is
less convenient than a hand rolled error type.
So, if we decide not to use error_chain, we now have a new set of problems if we
decide interoperability with error_chain is important. The first problem we run
into is that there are two natural bounds for wrapped errors that we would
pick, (Error + Send + Sync), or just Error, and neither of them will
interoperate well with error_chain. (Error + Send + Sync) means we can't wrap
error chain errors into LuaError::ExternalError (they're missing the Sync
bound), and having the bounds be just Error means the opposite, that we can't
hold a LuaError inside an error_chain error.
We could just decide that interoperability with error_chain is the most
important qualification, and pick (Error + Send), but this causes a DIFFERENT
set of problems. The rust ecosystem has the two primary error bounds as Error
or (Error + Send + Sync), and there are Into impls from &str / String to
Box<Error + Send + Sync> for example, but NOT (Error + Send). This means that
we are forced to manually recreate the conversions from &str / String to
LuaError rather than relying on a single Into<Box<Error + Send + Sync>> bound,
but this means that string conversions have a different set of methods than
other error types for external error conversion. I have not been able to figure
out an API that I am happy with that uses the (Error + Send) bound. Box<Error>
is obnoxious because not having errors implement Send causes needless problems
in a multithreaded context, so that leaves (Error + Send + Sync). This is
actually a completely reasonable bound for external errors, and has the nice
String Into impls that we would want, the ONLY problem is that it is a pain to
interoperate with the current version of error_chain.
It would be nice to be able to specify the traits that an error generated by the
error_chain macro would implement, and this is apparently in progress in the
error_chain library. This would solve both the problem with not being able to
implement Clone and the problems with (Error + Send) bounds. I am not convinced
that this library should go back to using error_chain when that functionality is
in stable error_chain though, because of the other minor usability problems with
using error_chain.
In that theoretical situation, the downside of NOT using error_chain is simply
that there would not be automatic stacktraces of LuaError. This is not a huge
problem, because stack traces of lua errors are not extremely useful, and for
external errors it is not too hard to create a different version of the
LuaExternalResult / LuaExternalError traits and do conversion from an
error_chain type into a type that will print the stacktrace on display, or
use downcasting in the error causes.
So in summary, this library is no longer using error_chain, and probably will
not use it again in the future. Currently this means that to interoperate with
error_chain, you should use error_chain 0.8.1, which derives Sync on errors, or
wait for a version that supports user defined trait derives. In the future
when error_chain supports user defined trait derives, users may have to take an
extra step to make wrapped external errors print the stacktrace that they
capture.
This change works, but is not entirely complete. There is no error
documentation yet, and the change brought to a head an ugly module organization
problem. There will be more commits for documentation and reorganization, then
a new stable version of rlua.
2017-06-24 18:11:56 -04:00
|
|
|
{
|
2017-07-18 16:21:12 -04:00
|
|
|
fn to_lua_err(self) -> Error {
|
Big API incompatible error change, remove dependency on error_chain
The current situation with error_chain is less than ideal, and there are lots of
conflicting interests that are impossible to meet at once. Here is an
unorganized brain dump of the current situation, stay awhile and listen!
This change was triggered ultimately by the desire to make LuaError implement
Clone, and this is currently impossible with error_chain. LuaError must
implement Clone to be a proper lua citizen that can live as userdata within a
lua runtime, because there is no way to limit what the lua runtime can do with a
received error. Currently, this is solved by there being a rule that the error
will "expire" if the error is passed back into rust, and this is very
sub-optimal. In fact, one could easily imagine a scenario where lua is for
example memoizing some function, and if the function has ever errored in the
past the function should continue returning the same error, and this situation
immediately fails with this restriciton in place.
Additionally, there are other more minor problems with error_chain which make
the API less good than it could be, or limit how we can use error_chain. This
change has already solved a small bug in a Chucklefish project, where the
conversion from an external error type (Borrow[Mut]Error) was allowed but not
intended for user code, and was accidentally used. Additionally, pattern
matching on error_chain errors, which should be common when dealing with Lua, is
less convenient than a hand rolled error type.
So, if we decide not to use error_chain, we now have a new set of problems if we
decide interoperability with error_chain is important. The first problem we run
into is that there are two natural bounds for wrapped errors that we would
pick, (Error + Send + Sync), or just Error, and neither of them will
interoperate well with error_chain. (Error + Send + Sync) means we can't wrap
error chain errors into LuaError::ExternalError (they're missing the Sync
bound), and having the bounds be just Error means the opposite, that we can't
hold a LuaError inside an error_chain error.
We could just decide that interoperability with error_chain is the most
important qualification, and pick (Error + Send), but this causes a DIFFERENT
set of problems. The rust ecosystem has the two primary error bounds as Error
or (Error + Send + Sync), and there are Into impls from &str / String to
Box<Error + Send + Sync> for example, but NOT (Error + Send). This means that
we are forced to manually recreate the conversions from &str / String to
LuaError rather than relying on a single Into<Box<Error + Send + Sync>> bound,
but this means that string conversions have a different set of methods than
other error types for external error conversion. I have not been able to figure
out an API that I am happy with that uses the (Error + Send) bound. Box<Error>
is obnoxious because not having errors implement Send causes needless problems
in a multithreaded context, so that leaves (Error + Send + Sync). This is
actually a completely reasonable bound for external errors, and has the nice
String Into impls that we would want, the ONLY problem is that it is a pain to
interoperate with the current version of error_chain.
It would be nice to be able to specify the traits that an error generated by the
error_chain macro would implement, and this is apparently in progress in the
error_chain library. This would solve both the problem with not being able to
implement Clone and the problems with (Error + Send) bounds. I am not convinced
that this library should go back to using error_chain when that functionality is
in stable error_chain though, because of the other minor usability problems with
using error_chain.
In that theoretical situation, the downside of NOT using error_chain is simply
that there would not be automatic stacktraces of LuaError. This is not a huge
problem, because stack traces of lua errors are not extremely useful, and for
external errors it is not too hard to create a different version of the
LuaExternalResult / LuaExternalError traits and do conversion from an
error_chain type into a type that will print the stacktrace on display, or
use downcasting in the error causes.
So in summary, this library is no longer using error_chain, and probably will
not use it again in the future. Currently this means that to interoperate with
error_chain, you should use error_chain 0.8.1, which derives Sync on errors, or
wait for a version that supports user defined trait derives. In the future
when error_chain supports user defined trait derives, users may have to take an
extra step to make wrapped external errors print the stacktrace that they
capture.
This change works, but is not entirely complete. There is no error
documentation yet, and the change brought to a head an ugly module organization
problem. There will be more commits for documentation and reorganization, then
a new stable version of rlua.
2017-06-24 18:11:56 -04:00
|
|
|
#[derive(Debug)]
|
2017-07-24 07:30:29 -04:00
|
|
|
struct WrapError(Box<StdError + Send + Sync>);
|
Big API incompatible error change, remove dependency on error_chain
The current situation with error_chain is less than ideal, and there are lots of
conflicting interests that are impossible to meet at once. Here is an
unorganized brain dump of the current situation, stay awhile and listen!
This change was triggered ultimately by the desire to make LuaError implement
Clone, and this is currently impossible with error_chain. LuaError must
implement Clone to be a proper lua citizen that can live as userdata within a
lua runtime, because there is no way to limit what the lua runtime can do with a
received error. Currently, this is solved by there being a rule that the error
will "expire" if the error is passed back into rust, and this is very
sub-optimal. In fact, one could easily imagine a scenario where lua is for
example memoizing some function, and if the function has ever errored in the
past the function should continue returning the same error, and this situation
immediately fails with this restriciton in place.
Additionally, there are other more minor problems with error_chain which make
the API less good than it could be, or limit how we can use error_chain. This
change has already solved a small bug in a Chucklefish project, where the
conversion from an external error type (Borrow[Mut]Error) was allowed but not
intended for user code, and was accidentally used. Additionally, pattern
matching on error_chain errors, which should be common when dealing with Lua, is
less convenient than a hand rolled error type.
So, if we decide not to use error_chain, we now have a new set of problems if we
decide interoperability with error_chain is important. The first problem we run
into is that there are two natural bounds for wrapped errors that we would
pick, (Error + Send + Sync), or just Error, and neither of them will
interoperate well with error_chain. (Error + Send + Sync) means we can't wrap
error chain errors into LuaError::ExternalError (they're missing the Sync
bound), and having the bounds be just Error means the opposite, that we can't
hold a LuaError inside an error_chain error.
We could just decide that interoperability with error_chain is the most
important qualification, and pick (Error + Send), but this causes a DIFFERENT
set of problems. The rust ecosystem has the two primary error bounds as Error
or (Error + Send + Sync), and there are Into impls from &str / String to
Box<Error + Send + Sync> for example, but NOT (Error + Send). This means that
we are forced to manually recreate the conversions from &str / String to
LuaError rather than relying on a single Into<Box<Error + Send + Sync>> bound,
but this means that string conversions have a different set of methods than
other error types for external error conversion. I have not been able to figure
out an API that I am happy with that uses the (Error + Send) bound. Box<Error>
is obnoxious because not having errors implement Send causes needless problems
in a multithreaded context, so that leaves (Error + Send + Sync). This is
actually a completely reasonable bound for external errors, and has the nice
String Into impls that we would want, the ONLY problem is that it is a pain to
interoperate with the current version of error_chain.
It would be nice to be able to specify the traits that an error generated by the
error_chain macro would implement, and this is apparently in progress in the
error_chain library. This would solve both the problem with not being able to
implement Clone and the problems with (Error + Send) bounds. I am not convinced
that this library should go back to using error_chain when that functionality is
in stable error_chain though, because of the other minor usability problems with
using error_chain.
In that theoretical situation, the downside of NOT using error_chain is simply
that there would not be automatic stacktraces of LuaError. This is not a huge
problem, because stack traces of lua errors are not extremely useful, and for
external errors it is not too hard to create a different version of the
LuaExternalResult / LuaExternalError traits and do conversion from an
error_chain type into a type that will print the stacktrace on display, or
use downcasting in the error causes.
So in summary, this library is no longer using error_chain, and probably will
not use it again in the future. Currently this means that to interoperate with
error_chain, you should use error_chain 0.8.1, which derives Sync on errors, or
wait for a version that supports user defined trait derives. In the future
when error_chain supports user defined trait derives, users may have to take an
extra step to make wrapped external errors print the stacktrace that they
capture.
This change works, but is not entirely complete. There is no error
documentation yet, and the change brought to a head an ugly module organization
problem. There will be more commits for documentation and reorganization, then
a new stable version of rlua.
2017-06-24 18:11:56 -04:00
|
|
|
|
|
|
|
impl fmt::Display for WrapError {
|
|
|
|
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
|
|
|
|
self.0.fmt(f)
|
|
|
|
}
|
2017-05-22 14:24:19 -04:00
|
|
|
}
|
Big API incompatible error change, remove dependency on error_chain
The current situation with error_chain is less than ideal, and there are lots of
conflicting interests that are impossible to meet at once. Here is an
unorganized brain dump of the current situation, stay awhile and listen!
This change was triggered ultimately by the desire to make LuaError implement
Clone, and this is currently impossible with error_chain. LuaError must
implement Clone to be a proper lua citizen that can live as userdata within a
lua runtime, because there is no way to limit what the lua runtime can do with a
received error. Currently, this is solved by there being a rule that the error
will "expire" if the error is passed back into rust, and this is very
sub-optimal. In fact, one could easily imagine a scenario where lua is for
example memoizing some function, and if the function has ever errored in the
past the function should continue returning the same error, and this situation
immediately fails with this restriciton in place.
Additionally, there are other more minor problems with error_chain which make
the API less good than it could be, or limit how we can use error_chain. This
change has already solved a small bug in a Chucklefish project, where the
conversion from an external error type (Borrow[Mut]Error) was allowed but not
intended for user code, and was accidentally used. Additionally, pattern
matching on error_chain errors, which should be common when dealing with Lua, is
less convenient than a hand rolled error type.
So, if we decide not to use error_chain, we now have a new set of problems if we
decide interoperability with error_chain is important. The first problem we run
into is that there are two natural bounds for wrapped errors that we would
pick, (Error + Send + Sync), or just Error, and neither of them will
interoperate well with error_chain. (Error + Send + Sync) means we can't wrap
error chain errors into LuaError::ExternalError (they're missing the Sync
bound), and having the bounds be just Error means the opposite, that we can't
hold a LuaError inside an error_chain error.
We could just decide that interoperability with error_chain is the most
important qualification, and pick (Error + Send), but this causes a DIFFERENT
set of problems. The rust ecosystem has the two primary error bounds as Error
or (Error + Send + Sync), and there are Into impls from &str / String to
Box<Error + Send + Sync> for example, but NOT (Error + Send). This means that
we are forced to manually recreate the conversions from &str / String to
LuaError rather than relying on a single Into<Box<Error + Send + Sync>> bound,
but this means that string conversions have a different set of methods than
other error types for external error conversion. I have not been able to figure
out an API that I am happy with that uses the (Error + Send) bound. Box<Error>
is obnoxious because not having errors implement Send causes needless problems
in a multithreaded context, so that leaves (Error + Send + Sync). This is
actually a completely reasonable bound for external errors, and has the nice
String Into impls that we would want, the ONLY problem is that it is a pain to
interoperate with the current version of error_chain.
It would be nice to be able to specify the traits that an error generated by the
error_chain macro would implement, and this is apparently in progress in the
error_chain library. This would solve both the problem with not being able to
implement Clone and the problems with (Error + Send) bounds. I am not convinced
that this library should go back to using error_chain when that functionality is
in stable error_chain though, because of the other minor usability problems with
using error_chain.
In that theoretical situation, the downside of NOT using error_chain is simply
that there would not be automatic stacktraces of LuaError. This is not a huge
problem, because stack traces of lua errors are not extremely useful, and for
external errors it is not too hard to create a different version of the
LuaExternalResult / LuaExternalError traits and do conversion from an
error_chain type into a type that will print the stacktrace on display, or
use downcasting in the error causes.
So in summary, this library is no longer using error_chain, and probably will
not use it again in the future. Currently this means that to interoperate with
error_chain, you should use error_chain 0.8.1, which derives Sync on errors, or
wait for a version that supports user defined trait derives. In the future
when error_chain supports user defined trait derives, users may have to take an
extra step to make wrapped external errors print the stacktrace that they
capture.
This change works, but is not entirely complete. There is no error
documentation yet, and the change brought to a head an ugly module organization
problem. There will be more commits for documentation and reorganization, then
a new stable version of rlua.
2017-06-24 18:11:56 -04:00
|
|
|
|
2017-07-24 07:30:29 -04:00
|
|
|
impl StdError for WrapError {
|
Big API incompatible error change, remove dependency on error_chain
The current situation with error_chain is less than ideal, and there are lots of
conflicting interests that are impossible to meet at once. Here is an
unorganized brain dump of the current situation, stay awhile and listen!
This change was triggered ultimately by the desire to make LuaError implement
Clone, and this is currently impossible with error_chain. LuaError must
implement Clone to be a proper lua citizen that can live as userdata within a
lua runtime, because there is no way to limit what the lua runtime can do with a
received error. Currently, this is solved by there being a rule that the error
will "expire" if the error is passed back into rust, and this is very
sub-optimal. In fact, one could easily imagine a scenario where lua is for
example memoizing some function, and if the function has ever errored in the
past the function should continue returning the same error, and this situation
immediately fails with this restriciton in place.
Additionally, there are other more minor problems with error_chain which make
the API less good than it could be, or limit how we can use error_chain. This
change has already solved a small bug in a Chucklefish project, where the
conversion from an external error type (Borrow[Mut]Error) was allowed but not
intended for user code, and was accidentally used. Additionally, pattern
matching on error_chain errors, which should be common when dealing with Lua, is
less convenient than a hand rolled error type.
So, if we decide not to use error_chain, we now have a new set of problems if we
decide interoperability with error_chain is important. The first problem we run
into is that there are two natural bounds for wrapped errors that we would
pick, (Error + Send + Sync), or just Error, and neither of them will
interoperate well with error_chain. (Error + Send + Sync) means we can't wrap
error chain errors into LuaError::ExternalError (they're missing the Sync
bound), and having the bounds be just Error means the opposite, that we can't
hold a LuaError inside an error_chain error.
We could just decide that interoperability with error_chain is the most
important qualification, and pick (Error + Send), but this causes a DIFFERENT
set of problems. The rust ecosystem has the two primary error bounds as Error
or (Error + Send + Sync), and there are Into impls from &str / String to
Box<Error + Send + Sync> for example, but NOT (Error + Send). This means that
we are forced to manually recreate the conversions from &str / String to
LuaError rather than relying on a single Into<Box<Error + Send + Sync>> bound,
but this means that string conversions have a different set of methods than
other error types for external error conversion. I have not been able to figure
out an API that I am happy with that uses the (Error + Send) bound. Box<Error>
is obnoxious because not having errors implement Send causes needless problems
in a multithreaded context, so that leaves (Error + Send + Sync). This is
actually a completely reasonable bound for external errors, and has the nice
String Into impls that we would want, the ONLY problem is that it is a pain to
interoperate with the current version of error_chain.
It would be nice to be able to specify the traits that an error generated by the
error_chain macro would implement, and this is apparently in progress in the
error_chain library. This would solve both the problem with not being able to
implement Clone and the problems with (Error + Send) bounds. I am not convinced
that this library should go back to using error_chain when that functionality is
in stable error_chain though, because of the other minor usability problems with
using error_chain.
In that theoretical situation, the downside of NOT using error_chain is simply
that there would not be automatic stacktraces of LuaError. This is not a huge
problem, because stack traces of lua errors are not extremely useful, and for
external errors it is not too hard to create a different version of the
LuaExternalResult / LuaExternalError traits and do conversion from an
error_chain type into a type that will print the stacktrace on display, or
use downcasting in the error causes.
So in summary, this library is no longer using error_chain, and probably will
not use it again in the future. Currently this means that to interoperate with
error_chain, you should use error_chain 0.8.1, which derives Sync on errors, or
wait for a version that supports user defined trait derives. In the future
when error_chain supports user defined trait derives, users may have to take an
extra step to make wrapped external errors print the stacktrace that they
capture.
This change works, but is not entirely complete. There is no error
documentation yet, and the change brought to a head an ugly module organization
problem. There will be more commits for documentation and reorganization, then
a new stable version of rlua.
2017-06-24 18:11:56 -04:00
|
|
|
fn description(&self) -> &str {
|
|
|
|
self.0.description()
|
|
|
|
}
|
2017-06-17 23:50:40 -04:00
|
|
|
}
|
2017-05-21 19:50:59 -04:00
|
|
|
|
2017-07-18 16:21:12 -04:00
|
|
|
Error::external(WrapError(self.into()))
|
2017-05-21 19:50:59 -04:00
|
|
|
}
|
|
|
|
}
|
|
|
|
|
2017-07-24 07:12:52 -04:00
|
|
|
pub trait ExternalResult<T> {
|
2017-07-18 16:21:12 -04:00
|
|
|
fn to_lua_err(self) -> Result<T>;
|
2017-05-21 19:50:59 -04:00
|
|
|
}
|
|
|
|
|
2017-07-24 07:30:29 -04:00
|
|
|
impl<T, E> ExternalResult<T> for StdResult<T, E>
|
2017-06-15 10:26:39 -04:00
|
|
|
where
|
2017-07-24 07:12:52 -04:00
|
|
|
E: ExternalError,
|
2017-05-21 19:50:59 -04:00
|
|
|
{
|
2017-07-18 16:21:12 -04:00
|
|
|
fn to_lua_err(self) -> Result<T> {
|
Big API incompatible error change, remove dependency on error_chain
The current situation with error_chain is less than ideal, and there are lots of
conflicting interests that are impossible to meet at once. Here is an
unorganized brain dump of the current situation, stay awhile and listen!
This change was triggered ultimately by the desire to make LuaError implement
Clone, and this is currently impossible with error_chain. LuaError must
implement Clone to be a proper lua citizen that can live as userdata within a
lua runtime, because there is no way to limit what the lua runtime can do with a
received error. Currently, this is solved by there being a rule that the error
will "expire" if the error is passed back into rust, and this is very
sub-optimal. In fact, one could easily imagine a scenario where lua is for
example memoizing some function, and if the function has ever errored in the
past the function should continue returning the same error, and this situation
immediately fails with this restriciton in place.
Additionally, there are other more minor problems with error_chain which make
the API less good than it could be, or limit how we can use error_chain. This
change has already solved a small bug in a Chucklefish project, where the
conversion from an external error type (Borrow[Mut]Error) was allowed but not
intended for user code, and was accidentally used. Additionally, pattern
matching on error_chain errors, which should be common when dealing with Lua, is
less convenient than a hand rolled error type.
So, if we decide not to use error_chain, we now have a new set of problems if we
decide interoperability with error_chain is important. The first problem we run
into is that there are two natural bounds for wrapped errors that we would
pick, (Error + Send + Sync), or just Error, and neither of them will
interoperate well with error_chain. (Error + Send + Sync) means we can't wrap
error chain errors into LuaError::ExternalError (they're missing the Sync
bound), and having the bounds be just Error means the opposite, that we can't
hold a LuaError inside an error_chain error.
We could just decide that interoperability with error_chain is the most
important qualification, and pick (Error + Send), but this causes a DIFFERENT
set of problems. The rust ecosystem has the two primary error bounds as Error
or (Error + Send + Sync), and there are Into impls from &str / String to
Box<Error + Send + Sync> for example, but NOT (Error + Send). This means that
we are forced to manually recreate the conversions from &str / String to
LuaError rather than relying on a single Into<Box<Error + Send + Sync>> bound,
but this means that string conversions have a different set of methods than
other error types for external error conversion. I have not been able to figure
out an API that I am happy with that uses the (Error + Send) bound. Box<Error>
is obnoxious because not having errors implement Send causes needless problems
in a multithreaded context, so that leaves (Error + Send + Sync). This is
actually a completely reasonable bound for external errors, and has the nice
String Into impls that we would want, the ONLY problem is that it is a pain to
interoperate with the current version of error_chain.
It would be nice to be able to specify the traits that an error generated by the
error_chain macro would implement, and this is apparently in progress in the
error_chain library. This would solve both the problem with not being able to
implement Clone and the problems with (Error + Send) bounds. I am not convinced
that this library should go back to using error_chain when that functionality is
in stable error_chain though, because of the other minor usability problems with
using error_chain.
In that theoretical situation, the downside of NOT using error_chain is simply
that there would not be automatic stacktraces of LuaError. This is not a huge
problem, because stack traces of lua errors are not extremely useful, and for
external errors it is not too hard to create a different version of the
LuaExternalResult / LuaExternalError traits and do conversion from an
error_chain type into a type that will print the stacktrace on display, or
use downcasting in the error causes.
So in summary, this library is no longer using error_chain, and probably will
not use it again in the future. Currently this means that to interoperate with
error_chain, you should use error_chain 0.8.1, which derives Sync on errors, or
wait for a version that supports user defined trait derives. In the future
when error_chain supports user defined trait derives, users may have to take an
extra step to make wrapped external errors print the stacktrace that they
capture.
This change works, but is not entirely complete. There is no error
documentation yet, and the change brought to a head an ugly module organization
problem. There will be more commits for documentation and reorganization, then
a new stable version of rlua.
2017-06-24 18:11:56 -04:00
|
|
|
self.map_err(|e| e.to_lua_err())
|
2017-05-21 19:50:59 -04:00
|
|
|
}
|
|
|
|
}
|