Add mlua_derive proc macro module

Cargo.toml

@@ -13,6 +13,11 @@ license = "MIT"
 # [badges]
 # travis-ci = { repository = "khvzak/mlua", branch = "master" }
 
+[workspace]
+members = [
+    "mlua_derive",
+]
+
 [dependencies]
 libc = { version = "0.2" }
 num-traits = { version = "0.2.6" }

mlua_derive/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "mlua_derive"
+version = "0.1.0"
+authors = ["Alex Orlenko <zxteam@protonmail.com>"]
+edition = "2018"
+
+[lib]
+proc-macro = true
+
+[dependencies]
+proc-macro2 = "1.0"
+quote = "1.0"
+syn = { version = "1.0", features = ["full"] }

mlua_derive/src/lib.rs

@@ -0,0 +1,35 @@
+extern crate proc_macro;
+
+use proc_macro::TokenStream;
+use proc_macro2::{Ident, Span};
+use quote::quote_spanned;
+use syn::{parse_macro_input, spanned::Spanned, AttributeArgs, Error, ItemFn};
+
+#[proc_macro_attribute]
+pub fn lua_module(attr: TokenStream, item: TokenStream) -> TokenStream {
+    let args = parse_macro_input!(attr as AttributeArgs);
+    let item = parse_macro_input!(item as ItemFn);
+
+    if args.len() > 0 {
+        let err = Error::new(Span::call_site(), "the number of arguments must be zero")
+            .to_compile_error();
+        return err.into();
+    }
+
+    let span = item.span();
+    let item_name = item.sig.ident.clone();
+    let ext_entrypoint_name = Ident::new(&format!("luaopen_{}", item.sig.ident), Span::call_site());
+
+    let wrapped = quote_spanned! { span =>
+        #[no_mangle]
+        unsafe extern "C" fn #ext_entrypoint_name(state: *mut mlua::lua_State) -> std::os::raw::c_int {
+            #item
+
+            mlua::Lua::init_from_ptr(state)
+                .entrypoint1(#item_name)
+                .unwrap()
+        }
+    };
+
+    wrapped.into()
+}

src/lua.rs

@@ -100,6 +100,18 @@ impl Lua {
         }
     }
 
+    // Executes module entrypoint function, which returns only one Value.
+    // The returned value then pushed to the Lua stack.
+    #[doc(hidden)]
+    pub fn entrypoint1<'lua, 'callback, R, F>(&'lua self, func: F) -> Result<c_int>
+    where
+        R: ToLua<'callback>,
+        F: 'static + Send + Fn(&'callback Lua) -> Result<R>,
+    {
+        let cb = self.create_callback(Box::new(move |lua, _| func(lua)?.to_lua_multi(lua)))?;
+        unsafe { self.push_value(cb.call(())?).map(|_| 1) }
+    }
+
     /// Returns true if the garbage collector is currently running automatically.
     pub fn gc_is_running(&self) -> bool {
         unsafe { ffi::lua_gc(self.main_state, ffi::LUA_GCISRUNNING, 0) != 0 }
@@ -718,8 +730,7 @@ impl Lua {
     }
 
     // Uses 2 stack spaces, does not call checkstack
-    // TODO: return to original
-    pub unsafe fn push_value(&self, value: Value) -> Result<()> {
+    pub(crate) unsafe fn push_value(&self, value: Value) -> Result<()> {
         match value {
             Value::Nil => {
                 ffi::lua_pushnil(self.state);
@@ -770,8 +781,7 @@ impl Lua {
     }
 
     // Uses 2 stack spaces, does not call checkstack
-    // TODO: return to original
-    pub unsafe fn pop_value(&self) -> Value {
+    pub(crate) unsafe fn pop_value(&self) -> Value {
         match ffi::lua_type(self.state, -1) {
             ffi::LUA_TNIL => {
                 ffi::lua_pop(self.state, 1);