Add support for renaming a struct field with js_name (#2360)

* Add support for renaming a field on the JS side using js_name

* Fix cargo fmt

crates/backend/src/ast.rs

@@ -238,7 +238,8 @@ pub struct Struct {
 #[cfg_attr(feature = "extra-traits", derive(Debug, PartialEq, Eq))]
 #[derive(Clone)]
 pub struct StructField {
-    pub name: syn::Member,
+    pub rust_name: syn::Member,
+    pub js_name: String,
     pub struct_name: Ident,
     pub readonly: bool,
     pub ty: syn::Type,

crates/backend/src/codegen.rs

@@ -264,7 +264,7 @@ impl ToTokens for ast::Struct {
 
 impl ToTokens for ast::StructField {
     fn to_tokens(&self, tokens: &mut TokenStream) {
-        let name = &self.name;
+        let rust_name = &self.rust_name;
         let struct_name = &self.struct_name;
         let ty = &self.ty;
         let getter = &self.getter;
@@ -287,7 +287,7 @@ impl ToTokens for ast::StructField {
 
                 let js = js as *mut WasmRefCell<#struct_name>;
                 assert_not_null(js);
-                let val = (*js).borrow().#name;
+                let val = (*js).borrow().#rust_name;
                 <#ty as IntoWasmAbi>::into_abi(val)
             }
         })
@@ -321,7 +321,7 @@ impl ToTokens for ast::StructField {
                 let js = js as *mut WasmRefCell<#struct_name>;
                 assert_not_null(js);
                 let val = <#ty as FromWasmAbi>::from_abi(val);
-                (*js).borrow_mut().#name = val;
+                (*js).borrow_mut().#rust_name = val;
             }
         })
         .to_tokens(tokens);

crates/backend/src/encode.rs

@@ -314,12 +314,9 @@ fn shared_struct<'a>(s: &'a ast::Struct, intern: &'a Interner) -> Struct<'a> {
     }
 }
 
-fn shared_struct_field<'a>(s: &'a ast::StructField, intern: &'a Interner) -> StructField<'a> {
+fn shared_struct_field<'a>(s: &'a ast::StructField, _intern: &'a Interner) -> StructField<'a> {
     StructField {
-        name: match &s.name {
-            syn::Member::Named(ident) => intern.intern(ident),
-            syn::Member::Unnamed(index) => intern.intern_str(&index.index.to_string()),
-        },
+        name: &s.js_name,
         readonly: s.readonly,
         comments: s.comments.iter().map(|s| &**s).collect(),
         generate_typescript: s.generate_typescript,

crates/macro-support/src/parser.rs

@@ -380,7 +380,7 @@ impl<'a> ConvertToAst<BindgenAttrs> for &'a mut syn::ItemStruct {
                 syn::Visibility::Public(..) => {}
                 _ => continue,
             }
-            let (name_str, member) = match &field.ident {
+            let (js_field_name, member) = match &field.ident {
                 Some(ident) => (ident.to_string(), syn::Member::Named(ident.clone())),
                 None => (i.to_string(), syn::Member::Unnamed(i.into())),
             };
@@ -392,12 +392,18 @@ impl<'a> ConvertToAst<BindgenAttrs> for &'a mut syn::ItemStruct {
                 continue;
             }
 
+            let js_field_name = match attrs.js_name() {
+                Some((name, _)) => name.to_string(),
+                None => js_field_name,
+            };
+
             let comments = extract_doc_comments(&field.attrs);
-            let getter = shared::struct_field_get(&js_name, &name_str);
-            let setter = shared::struct_field_set(&js_name, &name_str);
+            let getter = shared::struct_field_get(&js_name, &js_field_name);
+            let setter = shared::struct_field_set(&js_name, &js_field_name);
 
             fields.push(ast::StructField {
-                name: member,
+                rust_name: member,
+                js_name: js_field_name,
                 struct_name: self.ident.clone(),
                 readonly: attrs.readonly().is_some(),
                 ty: field.ty.clone(),

tests/wasm/classes.js

@@ -147,6 +147,13 @@ exports.js_renamed_export = () => {
     x.bar(x);
 };
 
+exports.js_renamed_field = () => {
+    const x = new wasm.RenamedField();
+    assert.ok(x.bar === 3);
+
+    x.foo();
+}
+
 exports.js_conditional_bindings = () => {
     const x = new wasm.ConditionalBindings();
     x.free();

tests/wasm/classes.rs

@@ -22,6 +22,7 @@ extern "C" {
     fn js_js_rename();
     fn js_access_fields();
     fn js_renamed_export();
+    fn js_renamed_field();
     fn js_conditional_bindings();
 
     fn js_assert_none(a: Option<OptionClass>);
@@ -426,6 +427,27 @@ fn renamed_export() {
     js_renamed_export();
 }
 
+#[wasm_bindgen]
+pub struct RenamedField {
+    #[wasm_bindgen(js_name = bar)]
+    pub foo: u32,
+}
+
+#[wasm_bindgen(js_class = RenamedField)]
+impl RenamedField {
+    #[wasm_bindgen(constructor)]
+    pub fn new() -> RenamedField {
+        RenamedField { foo: 3 }
+    }
+
+    pub fn foo(&self) {}
+}
+
+#[wasm_bindgen_test]
+fn renamed_field() {
+    js_renamed_field();
+}
+
 #[cfg_attr(target_arch = "wasm32", wasm_bindgen)]
 pub struct ConditionalBindings {}