Only generate JS values for string enums if used (#4193)

CHANGELOG.md

@@ -16,6 +16,9 @@
 * Fixed methods with `self: &Self` consuming the object.
   [#4178](https://github.com/rustwasm/wasm-bindgen/pull/4178)
 
+* Fixed unused string enums generating JS values.
+  [#4193](https://github.com/rustwasm/wasm-bindgen/pull/4193)
+
 --------------------------------------------------------------------------------
 
 ## [0.2.95](https://github.com/rustwasm/wasm-bindgen/compare/0.2.94...0.2.95)

crates/cli-support/src/js/binding.rs

@@ -701,6 +701,7 @@ fn instruction(
 
         Instruction::WasmToStringEnum { name } => {
             let index = js.pop();
+            js.cx.expose_string_enum(name);
             js.push(wasm_to_string_enum(name, &index))
         }
 
@@ -709,11 +710,13 @@ fn instruction(
             // ["a","b","c"][index], the lookup will implicitly return map
             // the hole to undefined, because OOB indexes will return undefined.
             let index = js.pop();
+            js.cx.expose_string_enum(name);
             js.push(wasm_to_string_enum(name, &index))
         }
 
         Instruction::StringEnumToWasm { name, invalid } => {
             let enum_val = js.pop();
+            js.cx.expose_string_enum(name);
             js.push(string_enum_to_wasm(name, *invalid, &enum_val))
         }
 
@@ -723,6 +726,7 @@ fn instruction(
             hole,
         } => {
             let enum_val = js.pop();
+            js.cx.expose_string_enum(name);
             let enum_val_expr = string_enum_to_wasm(name, *invalid, &enum_val);
             js.cx.expose_is_like_none();
 

crates/cli-support/src/js/mod.rs

@@ -52,6 +52,13 @@ pub struct Context<'a> {
     /// function signatures, etc.
     typescript_refs: HashSet<TsReference>,
 
+    /// String enums that are used internally by the generated bindings.
+    ///
+    /// This tracks which string enums are used independently from whether their
+    /// type is used, because users may only use them in a way that doesn't
+    /// require the type or requires only the type.
+    used_string_enums: HashSet<String>,
+
     exported_classes: Option<BTreeMap<String, ExportedClass>>,
 
     /// A map of the name of npm dependencies we've loaded so far to the path
@@ -114,6 +121,7 @@ impl<'a> Context<'a> {
             defined_identifiers: Default::default(),
             wasm_import_definitions: Default::default(),
             typescript_refs: Default::default(),
+            used_string_enums: Default::default(),
             exported_classes: Some(Default::default()),
             config,
             threads_enabled: config.threads.is_enabled(module),
@@ -3852,15 +3860,22 @@ __wbg_set_wasm(wasm);"
             self.typescript.push_str(";\n");
         }
 
-        self.global(&format!(
-            "const __wbindgen_enum_{name} = [{values}];\n",
-            name = string_enum.name,
-            values = variants.join(", ")
-        ));
+        if self.used_string_enums.contains(&string_enum.name) {
+            // only generate the internal string enum array if it's actually used
+            self.global(&format!(
+                "const __wbindgen_enum_{name} = [{values}];\n",
+                name = string_enum.name,
+                values = variants.join(", ")
+            ));
+        }
 
         Ok(())
     }
 
+    fn expose_string_enum(&mut self, string_enum_name: &str) {
+        self.used_string_enums.insert(string_enum_name.to_string());
+    }
+
     fn generate_struct(&mut self, struct_: &AuxStruct) -> Result<(), Error> {
         let class = require_class(&mut self.exported_classes, &struct_.name);
         class.comments = format_doc_comments(&struct_.comments, None);

crates/cli/tests/reference/enums.js

@@ -83,10 +83,6 @@ export const ImplicitDiscriminant = Object.freeze({ A:0,"0":"A",B:1,"1":"B",C:42
 
 const __wbindgen_enum_ColorName = ["green", "yellow", "red"];
 
-const __wbindgen_enum_FooBar = ["foo", "bar"];
-
-const __wbindgen_enum_PrivateStringEnum = ["foo", "bar"];
-
 export function __wbindgen_throw(arg0, arg1) {
     throw new Error(getStringFromWasm0(arg0, arg1));
 };

crates/cli/tests/reference/web-sys.js

@@ -210,8 +210,6 @@ function handleError(f, args) {
 
 const __wbindgen_enum_MediaSourceEnum = ["camera", "screen", "application", "window", "browser", "microphone", "audioCapture", "other"];
 
-const __wbindgen_enum_MediaSourceReadyState = ["closed", "open", "ended"];
-
 export function __wbg_new_1cabf49927794f50() { return handleError(function (arg0, arg1) {
     const ret = new URL(getStringFromWasm0(arg0, arg1));
     return addHeapObject(ret);