Remove Result from lua.null() and lua.array_metatable(). They never fail.

examples/async_http_reqwest.rs

@@ -4,7 +4,7 @@ use mlua::{Error, Lua, LuaSerdeExt, Result};
 async fn main() -> Result<()> {
     let lua = Lua::new();
     let globals = lua.globals();
-    globals.set("null", lua.null()?)?;
+    globals.set("null", lua.null())?;
 
     let fetch_json = lua.create_async_function(|lua, uri: String| async move {
         let resp = reqwest::get(&uri)

examples/serialize.rs

@@ -33,8 +33,8 @@ fn main() -> Result<()> {
     "#).eval()?)?;
 
     // Set it as (serializable) userdata
-    globals.set("null", lua.null()?)?;
+    globals.set("null", lua.null())?;
-    globals.set("array_mt", lua.array_metatable()?)?;
+    globals.set("array_mt", lua.array_metatable())?;
     globals.set("car", lua.create_ser_userdata(car)?)?;
 
     // Create a Lua table with multiple data types

src/serde/mod.rs

@@ -26,7 +26,7 @@ pub trait LuaSerdeExt<'lua> {
     ///
     /// fn main() -> Result<()> {
     ///     let lua = Lua::new();
-    ///     lua.globals().set("null", lua.null()?)?;
+    ///     lua.globals().set("null", lua.null())?;
     ///
     ///     let val = lua.load(r#"{a = null}"#).eval()?;
     ///     let map: HashMap<String, Option<String>> = lua.from_value(val)?;
@@ -35,7 +35,7 @@ pub trait LuaSerdeExt<'lua> {
     ///     Ok(())
     /// }
     /// ```
-    fn null(&'lua self) -> Result<Value<'lua>>;
+    fn null(&'lua self) -> Value<'lua>;
 
     /// A metatable attachable to a Lua table to systematically encode it as Array (instead of Map).
     /// As result, encoded Array will contain only sequence part of the table, with the same length
@@ -51,7 +51,7 @@ pub trait LuaSerdeExt<'lua> {
     ///
     /// fn main() -> Result<()> {
     ///     let lua = Lua::new();
-    ///     lua.globals().set("array_mt", lua.array_metatable()?)?;
+    ///     lua.globals().set("array_mt", lua.array_metatable())?;
     ///
     ///     // Encode as an empty array (no sequence part in the lua table)
     ///     let val = lua.load("setmetatable({a = 5}, array_mt)").eval()?;
@@ -66,7 +66,7 @@ pub trait LuaSerdeExt<'lua> {
     ///     Ok(())
     /// }
     /// ```
-    fn array_metatable(&'lua self) -> Result<Table<'lua>>;
+    fn array_metatable(&'lua self) -> Table<'lua>;
 
     /// Converts `T` into a `Value` instance.
     ///
@@ -162,19 +162,18 @@ pub trait LuaSerdeExt<'lua> {
 }
 
 impl<'lua> LuaSerdeExt<'lua> for Lua {
-    fn null(&'lua self) -> Result<Value<'lua>> {
+    fn null(&'lua self) -> Value<'lua> {
-        // TODO: Remove Result?
+        Value::LightUserData(LightUserData(ptr::null_mut()))
-        Ok(Value::LightUserData(LightUserData(ptr::null_mut())))
     }
 
-    fn array_metatable(&'lua self) -> Result<Table<'lua>> {
+    fn array_metatable(&'lua self) -> Table<'lua> {
         unsafe {
             let _sg = StackGuard::new(self.state);
             assert_stack(self.state, 1);
 
             push_array_metatable(self.state);
 
-            Ok(Table(self.pop_ref()))
+            Table(self.pop_ref())
         }
     }
 

src/serde/ser.rs

@@ -128,7 +128,7 @@ impl<'lua> ser::Serializer for Serializer<'lua> {
     #[inline]
     fn serialize_none(self) -> Result<Value<'lua>> {
         if self.options.serialize_none_to_null {
-            self.lua.null()
+            Ok(self.lua.null())
         } else {
             Ok(Value::Nil)
         }
@@ -145,7 +145,7 @@ impl<'lua> ser::Serializer for Serializer<'lua> {
     #[inline]
     fn serialize_unit(self) -> Result<Value<'lua>> {
         if self.options.serialize_unit_to_null {
-            self.lua.null()
+            Ok(self.lua.null())
         } else {
             Ok(Value::Nil)
         }
@@ -154,7 +154,7 @@ impl<'lua> ser::Serializer for Serializer<'lua> {
     #[inline]
     fn serialize_unit_struct(self, _name: &'static str) -> Result<Value<'lua>> {
         if self.options.serialize_unit_to_null {
-            self.lua.null()
+            Ok(self.lua.null())
         } else {
             Ok(Value::Nil)
         }
@@ -201,7 +201,7 @@ impl<'lua> ser::Serializer for Serializer<'lua> {
         let len = len.unwrap_or(0) as c_int;
         let table = self.lua.create_table_with_capacity(len, 0)?;
         if self.options.set_array_metatable {
-            table.set_metatable(Some(self.lua.array_metatable()?));
+            table.set_metatable(Some(self.lua.array_metatable()));
         }
         let options = self.options;
         Ok(SerializeVec { table, options })

tests/serde.rs

@@ -17,10 +17,10 @@ fn test_serialize() -> Result<(), Box<dyn std::error::Error>> {
 
     let ud = lua.create_ser_userdata(MyUserData(123, "test userdata".into()))?;
     globals.set("ud", ud)?;
-    globals.set("null", lua.null()?)?;
+    globals.set("null", lua.null())?;
 
     let empty_array = lua.create_table()?;
-    empty_array.set_metatable(Some(lua.array_metatable()?));
+    empty_array.set_metatable(Some(lua.array_metatable()));
     globals.set("empty_array", empty_array)?;
 
     let val = lua
@@ -145,7 +145,7 @@ fn test_serialize_failure() -> Result<(), Box<dyn std::error::Error>> {
 fn test_to_value_struct() -> LuaResult<()> {
     let lua = Lua::new();
     let globals = lua.globals();
-    globals.set("null", lua.null()?)?;
+    globals.set("null", lua.null())?;
 
     #[derive(Serialize)]
     struct Test {
@@ -175,7 +175,7 @@ fn test_to_value_struct() -> LuaResult<()> {
 fn test_to_value_enum() -> LuaResult<()> {
     let lua = Lua::new();
     let globals = lua.globals();
-    globals.set("null", lua.null()?)?;
+    globals.set("null", lua.null())?;
 
     #[derive(Serialize)]
     struct Test {
@@ -236,7 +236,7 @@ fn test_to_value_enum() -> LuaResult<()> {
 fn test_to_value_with_options() -> Result<(), Box<dyn std::error::Error>> {
     let lua = Lua::new();
     let globals = lua.globals();
-    globals.set("null", lua.null()?)?;
+    globals.set("null", lua.null())?;
 
     // set_array_metatable
     let data = lua.to_value_with(
@@ -386,7 +386,7 @@ fn test_from_value_enum() -> Result<(), Box<dyn std::error::Error>> {
 #[test]
 fn test_from_value_enum_untagged() -> Result<(), Box<dyn std::error::Error>> {
     let lua = Lua::new();
-    lua.globals().set("null", lua.null()?)?;
+    lua.globals().set("null", lua.null())?;
 
     #[derive(Deserialize, PartialEq, Debug)]
     #[serde(untagged)]