mlua_derive: Switch from #[userdata] to [derive(UserData)]

examples/userdata.rs

@@ -1,7 +1,6 @@
-use mlua::{Lua, Result, chunk};
+use mlua::{Lua, Result, UserData, chunk};
 
-#[derive(Default)]
-#[mlua::userdata]
+#[derive(Default, UserData)]
 struct Rectangle {
     length: u32,
     width: u32,

mlua_derive/src/lib.rs

@@ -33,11 +33,11 @@ pub fn from_lua(input: TokenStream) -> TokenStream {
     from_lua::from_lua(input)
 }
 
-/// Attribute macro for exposing a Rust type as a Lua userdata.
+/// Derive macro for implementing `UserData` for a Rust type.
 #[cfg(feature = "macros")]
-#[proc_macro_attribute]
-pub fn userdata(attr: TokenStream, item: TokenStream) -> TokenStream {
-    userdata::userdata_type(attr, item)
+#[proc_macro_derive(UserData, attributes(lua))]
+pub fn userdata(item: TokenStream) -> TokenStream {
+    userdata::userdata_type(item)
 }
 
 /// Attribute macro for exposing impl block methods to Lua userdata.

mlua_derive/src/userdata/mod.rs

@@ -34,35 +34,18 @@ fn parse_field_lua_attr(attrs: &[Attribute]) -> syn::Result<LuaAttr> {
     Ok(lua_attr)
 }
 
-/// Strip `#[lua(...)]` attributes from a field, keeping all others.
-fn strip_lua_attrs(attrs: &[Attribute]) -> Vec<Attribute> {
-    (attrs.iter())
-        .filter(|attr| !attr.path().is_ident("lua"))
-        .cloned()
-        .collect()
-}
-
-pub fn userdata_type(attr: TokenStream, item: TokenStream) -> TokenStream {
-    if !attr.is_empty() {
-        return Error::new_spanned(
-            proc_macro2::TokenStream::from(attr),
-            "`#[userdata]` does not accept arguments",
-        )
-        .to_compile_error()
-        .into();
-    }
-
-    let mut input = parse_macro_input!(item as DeriveInput);
+pub fn userdata_type(item: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(item as DeriveInput);
     let type_name = &input.ident;
 
-    let mut named_fields: Option<&mut FieldsNamed> = match &mut input.data {
-        Data::Struct(data) => match &mut data.fields {
+    let named_fields: Option<&FieldsNamed> = match &input.data {
+        Data::Struct(data) => match &data.fields {
             Fields::Named(fields) => Some(fields),
             Fields::Unnamed(_) | Fields::Unit => None,
         },
         Data::Enum(_) => None,
         Data::Union(_) => {
-            return Error::new_spanned(&input, "`#[userdata]` cannot be applied to unions")
+            return Error::new_spanned(&input, "`#[derive(UserData)]` cannot be applied to unions")
                 .to_compile_error()
                 .into();
         }
@@ -73,14 +56,14 @@ pub fn userdata_type(attr: TokenStream, item: TokenStream) -> TokenStream {
     if has_type_params {
         return Error::new_spanned(
             &input.generics,
-            "`#[userdata]` does not support generic type parameters. Wrap the generic type in a concrete newtype instead."
+            "`#[derive(UserData)]` does not support generic type parameters. Wrap the generic type in a concrete newtype instead."
         )
         .to_compile_error()
         .into();
     }
 
     let mut field_registrations = Vec::new();
-    if let Some(fields) = &mut named_fields {
+    if let Some(fields) = &named_fields {
         for field in &fields.named {
             let field_name = field.ident.as_ref().unwrap();
 
@@ -114,19 +97,12 @@ pub fn userdata_type(attr: TokenStream, item: TokenStream) -> TokenStream {
                 field_registrations.push(with_cfg(tokens, &field.attrs));
             }
         }
-
-        // Strip mlua-specific attributes from fields before re-emitting
-        for field in &mut fields.named {
-            field.attrs = strip_lua_attrs(&field.attrs);
-        }
     }
 
     let registration_type_name = format_ident!("__MluaUserDataRegistration_{type_name}");
     let register_fields_fn_name = format_ident!("__mlua_register_{type_name}_fields");
 
     let output = quote! {
-        #input
-
         #[doc(hidden)]
         #[allow(non_camel_case_types)]
         struct #registration_type_name {

src/lib.rs

@@ -233,16 +233,14 @@ pub use mlua_derive::chunk;
 #[cfg_attr(docsrs, doc(cfg(feature = "macros")))]
 pub use mlua_derive::FromLua;
 
-/// Attribute macro for exposing a struct as Lua userdata.
+/// Derive macro for implementing [`UserData`] for a Rust type.
 ///
-/// All fields are auto-exposed as get/set.
+/// Named fields are auto-exposed as get/set.
 ///
 /// Use `#[lua(...)]` to customize.
-///
-/// This generates a [`UserData`] trait implementation.
 #[cfg(feature = "macros")]
 #[cfg_attr(docsrs, doc(cfg(feature = "macros")))]
-pub use mlua_derive::userdata;
+pub use mlua_derive::UserData;
 
 /// Attribute macro for exposing impl block methods to Lua userdata.
 ///

tests/compile/userdata_const_getter.rs

@@ -1,5 +1,4 @@
-#[derive(Default)]
-#[mlua::userdata]
+#[derive(Default, mlua::UserData)]
 struct Foo;
 
 #[mlua::userdata_impl]

tests/compile/userdata_const_getter.stderr

@@ -1,5 +1,5 @@
 error: const items do not support `getter` or `setter`
- --> tests/compile/userdata_const_getter.rs:8:11
+ --> tests/compile/userdata_const_getter.rs:7:11
   |
-8 |     const X: u32 = 42;
+7 |     const X: u32 = 42;
   |           ^

tests/compile/userdata_field_async.rs

@@ -1,7 +1,6 @@
 use mlua::Result;
 
-#[derive(Clone, Debug)]
-#[mlua::userdata]
+#[derive(Clone, Debug, mlua::UserData)]
 struct Foo;
 
 #[mlua::userdata_impl]

tests/compile/userdata_field_async.stderr

@@ -1,8 +1,8 @@
 error: async field function is not supported
-  --> tests/compile/userdata_field_async.rs:10:5
-   |
-10 |     async fn description() -> Result<String> {
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ --> tests/compile/userdata_field_async.rs:9:5
+  |
+9 |     async fn description() -> Result<String> {
+  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused import: `mlua::Result`
  --> tests/compile/userdata_field_async.rs:1:5

tests/compile/userdata_field_with_args.rs

@@ -1,5 +1,4 @@
-#[derive(Default)]
-#[mlua::userdata]
+#[derive(Default, mlua::UserData)]
 struct Foo {
     x: u32,
 }

tests/compile/userdata_field_with_args.stderr

@@ -1,5 +1,5 @@
 error: field function must not take arguments
-  --> tests/compile/userdata_field_with_args.rs:10:5
-   |
-10 |     fn as_name(name: &str) -> String {
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ --> tests/compile/userdata_field_with_args.rs:9:5
+  |
+9 |     fn as_name(name: &str) -> String {
+  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

tests/compile/userdata_getter_and_meta.rs

@@ -1,5 +1,4 @@
-#[derive(Default)]
-#[mlua::userdata]
+#[derive(Default, mlua::UserData)]
 struct Foo;
 
 #[mlua::userdata_impl]

tests/compile/userdata_getter_and_meta.stderr

@@ -1,5 +1,5 @@
 error: `meta` can only be combined with `field`
- --> tests/compile/userdata_getter_and_meta.rs:8:5
+ --> tests/compile/userdata_getter_and_meta.rs:7:5
   |
-8 |     fn bar(&self) -> mlua::Result<u32> {
+7 |     fn bar(&self) -> mlua::Result<u32> {
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

tests/compile/userdata_getter_and_setter.rs

@@ -1,5 +1,4 @@
-#[derive(Default)]
-#[mlua::userdata]
+#[derive(Default, mlua::UserData)]
 struct Foo {
     x: u32,
 }

tests/compile/userdata_getter_and_setter.stderr

@@ -1,5 +1,5 @@
 error: at most one of `getter`, `setter`, `field` can be specified
-  --> tests/compile/userdata_getter_and_setter.rs:10:5
-   |
-10 |     fn x(&self) -> mlua::Result<u32> {
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ --> tests/compile/userdata_getter_and_setter.rs:9:5
+  |
+9 |     fn x(&self) -> mlua::Result<u32> {
+  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

tests/compile/userdata_getter_async.rs

@@ -1,7 +1,6 @@
 use mlua::Result;
 
-#[derive(Clone, Debug)]
-#[mlua::userdata]
+#[derive(Clone, Debug, mlua::UserData)]
 struct Foo(u64);
 
 #[mlua::userdata_impl]

tests/compile/userdata_getter_async.stderr

@@ -1,8 +1,8 @@
 error: async field getter is not supported
-  --> tests/compile/userdata_getter_async.rs:10:5
-   |
-10 |     async fn value(&self) -> Result<u64> {
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ --> tests/compile/userdata_getter_async.rs:9:5
+  |
+9 |     async fn value(&self) -> Result<u64> {
+  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused import: `mlua::Result`
  --> tests/compile/userdata_getter_async.rs:1:5

tests/compile/userdata_getter_extra_arg.rs

@@ -1,5 +1,4 @@
-#[derive(Default)]
-#[mlua::userdata]
+#[derive(Default, mlua::UserData)]
 struct Foo {
     x: u32,
 }

tests/compile/userdata_getter_extra_arg.stderr

@@ -1,5 +1,5 @@
 error: field getter must not take additional arguments
-  --> tests/compile/userdata_getter_extra_arg.rs:10:5
-   |
-10 |     fn x(&self, extra: u32) -> mlua::Result<u32> {
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ --> tests/compile/userdata_getter_extra_arg.rs:9:5
+  |
+9 |     fn x(&self, extra: u32) -> mlua::Result<u32> {
+  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

tests/compile/userdata_getter_mut_self.rs

@@ -1,5 +1,4 @@
-#[derive(Default)]
-#[mlua::userdata]
+#[derive(Default, mlua::UserData)]
 struct Foo {
     x: u32,
 }

tests/compile/userdata_getter_mut_self.stderr

@@ -1,5 +1,5 @@
 error: field getter must take `&self`
-  --> tests/compile/userdata_getter_mut_self.rs:10:5
-   |
-10 |     fn x(&mut self) -> mlua::Result<u32> {
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ --> tests/compile/userdata_getter_mut_self.rs:9:5
+  |
+9 |     fn x(&mut self) -> mlua::Result<u32> {
+  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

tests/compile/userdata_meta_owned_self.rs

@@ -1,5 +1,4 @@
-#[derive(Default)]
-#[mlua::userdata]
+#[derive(Default, mlua::UserData)]
 struct Foo;
 
 #[mlua::userdata_impl]

tests/compile/userdata_meta_owned_self.stderr

@@ -1,5 +1,5 @@
 error: meta methods cannot take `self`, use `&[mut] self` instead
- --> tests/compile/userdata_meta_owned_self.rs:8:5
+ --> tests/compile/userdata_meta_owned_self.rs:7:5
   |
-8 |     fn __gc(self) -> mlua::Result<()> {
+7 |     fn __gc(self) -> mlua::Result<()> {
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

tests/compile/userdata_mut_slice_arg.rs

@@ -1,5 +1,4 @@
-#[derive(Default)]
-#[mlua::userdata]
+#[derive(Default, mlua::UserData)]
 struct Foo(Vec<u8>);
 
 #[mlua::userdata_impl]

tests/compile/userdata_mut_slice_arg.stderr

@@ -1,5 +1,5 @@
 error: this reference type is not supported as a callback parameter
- --> tests/compile/userdata_mut_slice_arg.rs:7:27
+ --> tests/compile/userdata_mut_slice_arg.rs:6:27
   |
-7 |     fn first(&self, data: &mut [u8]) -> mlua::Result<u8> {
+6 |     fn first(&self, data: &mut [u8]) -> mlua::Result<u8> {
   |                           ^^^^^^^^^

tests/compile/userdata_setter_async.rs

@@ -1,7 +1,6 @@
 use mlua::Result;
 
-#[derive(Clone, Debug)]
-#[mlua::userdata]
+#[derive(Clone, Debug, mlua::UserData)]
 struct Foo(u64);
 
 #[mlua::userdata_impl]

tests/compile/userdata_setter_async.stderr

@@ -1,8 +1,8 @@
 error: async field setter is not supported
-  --> tests/compile/userdata_setter_async.rs:10:5
-   |
-10 |     async fn set_value(&mut self, val: u64) -> Result<()> {
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ --> tests/compile/userdata_setter_async.rs:9:5
+  |
+9 |     async fn set_value(&mut self, val: u64) -> Result<()> {
+  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 warning: unused import: `mlua::Result`
  --> tests/compile/userdata_setter_async.rs:1:5

tests/compile/userdata_setter_no_value.rs

@@ -1,5 +1,4 @@
-#[derive(Default)]
-#[mlua::userdata]
+#[derive(Default, mlua::UserData)]
 struct Foo {
     x: u32,
 }

tests/compile/userdata_setter_no_value.stderr

@@ -1,5 +1,5 @@
 error: field setter must take exactly one value argument
-  --> tests/compile/userdata_setter_no_value.rs:10:5
-   |
-10 |     fn set_x(&mut self) -> mlua::Result<()> {
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ --> tests/compile/userdata_setter_no_value.rs:9:5
+  |
+9 |     fn set_x(&mut self) -> mlua::Result<()> {
+  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

tests/compile/userdata_setter_ref_self.rs

@@ -1,5 +1,4 @@
-#[derive(Default)]
-#[mlua::userdata]
+#[derive(Default, mlua::UserData)]
 struct Foo {
     x: u32,
 }

tests/compile/userdata_setter_ref_self.stderr

@@ -1,5 +1,5 @@
 error: field setter must take `&[mut] self`
-  --> tests/compile/userdata_setter_ref_self.rs:10:5
-   |
-10 |     fn set_x(self, val: u32) -> mlua::Result<()> {
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ --> tests/compile/userdata_setter_ref_self.rs:9:5
+  |
+9 |     fn set_x(self, val: u32) -> mlua::Result<()> {
+  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

tests/compile/userdata_static_with_self.rs

@@ -1,5 +1,4 @@
-#[derive(Default)]
-#[mlua::userdata]
+#[derive(Default, mlua::UserData)]
 struct Foo {
     x: u32,
 }

tests/compile/userdata_static_with_self.stderr

@@ -1,5 +1,5 @@
 error: field function must not take `self`
-  --> tests/compile/userdata_static_with_self.rs:10:5
-   |
-10 |     fn get_x(&self) -> mlua::Result<u32> {
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+ --> tests/compile/userdata_static_with_self.rs:9:5
+  |
+9 |     fn get_x(&self) -> mlua::Result<u32> {
+  |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

tests/userdata_macro.rs

@@ -1,9 +1,8 @@
 #![cfg(feature = "macros")]
 
-use mlua::{Lua, Result};
+use mlua::{Lua, Result, UserData};
 
-#[derive(Default, Clone, Debug)]
-#[mlua::userdata]
+#[derive(Default, Clone, Debug, UserData)]
 struct Rectangle {
     length: u32,
     #[lua]
@@ -208,8 +207,7 @@ fn test_rectangle() {
     .unwrap();
 }
 
-#[derive(Clone, Debug)]
-#[mlua::userdata]
+#[derive(Clone, Debug, UserData)]
 enum Color {
     Red,
     Green,
@@ -274,8 +272,7 @@ fn test_color() {
     .unwrap();
 }
 
-#[derive(Clone, Debug)]
-#[mlua::userdata]
+#[derive(Clone, Debug, UserData)]
 struct Point(i32, i32);
 
 fn make_lua_point() -> Lua {
@@ -328,8 +325,7 @@ fn test_point() {
     .unwrap();
 }
 
-#[derive(Clone, Debug)]
-#[mlua::userdata]
+#[derive(Clone, Debug, UserData)]
 struct Bytes(Vec<u8>);
 
 #[mlua::userdata_impl]
@@ -375,10 +371,9 @@ fn test_known_borrow_wrappers() -> Result<()> {
 
 #[cfg(feature = "async")]
 mod async_tests {
-    use mlua::{Lua, Result};
+    use mlua::{Lua, Result, UserData};
 
-    #[derive(Clone, Debug)]
-    #[mlua::userdata]
+    #[derive(Clone, Debug, UserData)]
     struct AsyncCounter(u64);
 
     #[mlua::userdata_impl]