Add #[wasm_bindgen(assert_no_shim)] on imported functions for testing

This should not be used outside of wasm-bindgen's test suite.

crates/backend/src/ast.rs

@@ -122,6 +122,7 @@ pub struct ImportFunction {
     pub catch: bool,
     pub variadic: bool,
     pub structural: bool,
+    pub assert_no_shim: bool,
     pub kind: ImportFunctionKind,
     pub shim: Ident,
     pub doc_comment: Option<String>,

crates/backend/src/encode.rs

@@ -272,6 +272,7 @@ fn shared_import_function<'a>(
         shim: intern.intern(&i.shim),
         catch: i.catch,
         method,
+        assert_no_shim: i.assert_no_shim,
         structural: i.structural,
         function: shared_function(&i.function, intern),
         variadic: i.variadic,

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

@@ -1839,7 +1839,8 @@ impl<'a> Context<'a> {
         for (id, import) in sorted_iter(&aux.import_map) {
             let variadic = aux.imports_with_variadic.contains(&id);
             let catch = aux.imports_with_catch.contains(&id);
-            self.generate_import(*id, import, bindings, variadic, catch)
+            let assert_no_shim = aux.imports_with_assert_no_shim.contains(&id);
+            self.generate_import(*id, import, bindings, variadic, catch, assert_no_shim)
                 .with_context(|_| {
                     format!("failed to generate bindings for import `{:?}`", import,)
                 })?;
@@ -1978,6 +1979,7 @@ impl<'a> Context<'a> {
         bindings: &NonstandardWebidlSection,
         variadic: bool,
         catch: bool,
+        assert_no_shim: bool,
     ) -> Result<(), Error> {
         let binding = &bindings.imports[&id];
         let webidl = bindings
@@ -1996,6 +1998,13 @@ impl<'a> Context<'a> {
                 )
             }
             _ => {
+                if assert_no_shim {
+                    panic!(
+                        "imported function was annotated with `#[wasm_bindgen(assert_no_shim)]` \
+                         but we need to generate a JS shim for it"
+                    );
+                }
+
                 let mut builder = binding::Builder::new(self);
                 builder.catch(catch)?;
                 let js = builder.process(

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

@@ -163,6 +163,7 @@ pub struct WasmBindgenAux {
     /// Small bits of metadata about imports.
     pub imports_with_catch: HashSet<ImportId>,
     pub imports_with_variadic: HashSet<ImportId>,
+    pub imports_with_assert_no_shim: HashSet<ImportId>,
 
     /// Auxiliary information to go into JS/TypeScript bindings describing the
     /// exported enums from Rust.
@@ -793,6 +794,7 @@ impl<'a> Context<'a> {
             method,
             structural,
             function,
+            assert_no_shim,
         } = function;
         let (import_id, _id) = match self.function_imports.get(*shim) {
             Some(pair) => *pair,
@@ -811,6 +813,9 @@ impl<'a> Context<'a> {
         if *catch {
             self.aux.imports_with_catch.insert(import_id);
         }
+        if *assert_no_shim {
+            self.aux.imports_with_assert_no_shim.insert(import_id);
+        }
 
         // Perform two functions here. First we're saving off our WebIDL
         // bindings signature, indicating what we think our import is going to

crates/macro-support/src/parser.rs

@@ -52,6 +52,9 @@ macro_rules! attrgen {
             (typescript_custom_section, TypescriptCustomSection(Span)),
             (start, Start(Span)),
             (skip, Skip(Span)),
+
+            // For testing purposes only.
+            (assert_no_shim, AssertNoShim(Span)),
         }
     };
 }
@@ -496,8 +499,10 @@ impl<'a> ConvertToAst<(BindgenAttrs, &'a ast::ImportModule)> for syn::ForeignIte
                 return Err(Diagnostic::span_error(*span, msg));
             }
         }
+        let assert_no_shim = opts.assert_no_shim().is_some();
         let ret = ast::ImportKind::Function(ast::ImportFunction {
             function: wasm,
+            assert_no_shim,
             kind,
             js_ret,
             catch,

crates/shared/src/lib.rs

@@ -44,6 +44,7 @@ macro_rules! shared_api {
             shim: &'a str,
             catch: bool,
             variadic: bool,
+            assert_no_shim: bool,
             method: Option<MethodData<'a>>,
             structural: bool,
             function: Function<'a>,

crates/webidl/src/util.rs

@@ -314,6 +314,7 @@ impl<'src> FirstPassRecord<'src> {
             variadic,
             catch,
             structural,
+            assert_no_shim: false,
             shim: {
                 let ns = match kind {
                     ast::ImportFunctionKind::Normal => "",

tests/wasm/no_shims.rs

@@ -35,20 +35,30 @@ use wasm_bindgen_test::*;
     };
 ")]
 extern "C" {
+    #[wasm_bindgen(assert_no_shim)]
     fn trivial();
 
+    #[wasm_bindgen(assert_no_shim)]
     fn incoming_i32() -> i32;
+    #[wasm_bindgen(assert_no_shim)]
     fn incoming_f32() -> f32;
+    #[wasm_bindgen(assert_no_shim)]
     fn incoming_f64() -> f64;
 
+    #[wasm_bindgen(assert_no_shim)]
     fn outgoing_i32(x: i32);
+    #[wasm_bindgen(assert_no_shim)]
     fn outgoing_f32(y: f32);
+    #[wasm_bindgen(assert_no_shim)]
     fn outgoing_f64(z: f64);
 
+    #[wasm_bindgen(assert_no_shim)]
     fn many(x: i32, y: f32, z: f64) -> i32;
 
     // Note that this should only skip the JS shim if we have anyref support
     // enabled.
+    //
+    // #[wasm_bindgen(assert_no_shim)]
     fn works_when_anyref_support_is_enabled(v: JsValue) -> JsValue;
 }