Apply only allowed attributes to generated functions

crates/backend/src/codegen.rs

@@ -678,6 +678,14 @@ impl TryToTokens for ast::Export {
         };
         let nargs = self.function.arguments.len() as u32;
         let attrs = &self.function.rust_attrs;
+        let safe_attrs = attrs
+            .iter()
+            .filter(|a| {
+                let path = a.path();
+                path.is_ident("cfg") || path.is_ident("cfg_attr")
+            })
+            .cloned()
+            .collect::<Vec<_>>();
 
         let start_check = if self.start {
             quote! { const _ASSERT: fn() = || -> #projection::Abi { loop {} }; }
@@ -688,7 +696,7 @@ impl TryToTokens for ast::Export {
         (quote! {
             #[automatically_derived]
             const _: () = {
-                #(#attrs)*
+                #(#safe_attrs)*
                 #[cfg_attr(
                     all(target_arch = "wasm32", not(any(target_os = "emscripten", target_os = "wasi"))),
                     export_name = #export_name,
@@ -745,7 +753,7 @@ impl TryToTokens for ast::Export {
                 #describe_args
                 #describe_ret
             },
-            attrs: attrs.clone(),
+            attrs: safe_attrs,
             wasm_bindgen: &self.wasm_bindgen,
         }
         .to_tokens(into);

tests/wasm/attributes.js

@@ -0,0 +1,9 @@
+const wasm = require("wasm-bindgen-test.js");
+const assert = require("assert");
+
+exports.js_works = () => {
+  assert.strictEqual(wasm.valid_export(), true);
+  assert.strictEqual(wasm.invalid_export, undefined);
+  assert.strictEqual(wasm.valid_attr_export(), true);
+  assert.strictEqual(wasm.invalid_attr_export, undefined);
+};

tests/wasm/attributes.rs

@@ -0,0 +1,36 @@
+use wasm_bindgen::prelude::*;
+use wasm_bindgen_test::*;
+
+#[wasm_bindgen(module = "tests/wasm/attributes.js")]
+extern "C" {
+    fn js_works();
+}
+
+#[wasm_bindgen_test]
+fn works() {
+    js_works();
+}
+
+#[wasm_bindgen]
+#[cfg(target_arch = "wasm32")]
+pub fn valid_export() -> bool {
+    true
+}
+
+#[wasm_bindgen]
+#[cfg(not(target_arch = "wasm32"))]
+pub fn invalid_export() -> bool {
+    false
+}
+
+#[wasm_bindgen]
+#[cfg_attr(not(target_arch = "wasm32"), cfg(feature = "missing-feature"))]
+pub fn valid_attr_export() -> bool {
+    true
+}
+
+#[wasm_bindgen]
+#[cfg_attr(target_arch = "wasm32", cfg(feature = "missing-feature"))]
+pub fn invalid_attr_export() -> bool {
+    false
+}

tests/wasm/main.rs

@@ -16,6 +16,7 @@ use wasm_bindgen::prelude::*;
 
 pub mod api;
 pub mod arg_names;
+pub mod attributes;
 pub mod bigint;
 pub mod char;
 pub mod classes;