[WASM] JsInterop - In preparation for interfaces and other changes, remove the unused JS prototype from interface vtables

Some refactoring around AstUtils utility methods to allow interfaces to be treated separately.

PiperOrigin-RevId: 890019615

Author: Googler

transpiler/java/com/google/j2cl/transpiler/ast/AstUtils.java

@@ -1340,24 +1340,39 @@ public static boolean isAnnotatedWithWasm(HasAnnotations node) {
    * <p>A new prototype is populated if the type adds exported members.
    */
   public static boolean hasWasmJsPrototype(TypeDeclaration typeDeclaration) {
+    return !typeDeclaration.isInterface() && declaresWasmJsExports(typeDeclaration);
+  }
+
+  /** Returns true if the given type has any exported members in Wasm. */
+  public static boolean declaresWasmJsExports(TypeDeclaration typeDeclaration) {
     return !typeDeclaration.isNative()
-        && !typeDeclaration.isInterface()
         && (typeDeclaration.getDeclaredMethodDescriptors().stream()
                 .anyMatch(methodDescriptor -> AstUtils.needsWasmJsExport(methodDescriptor))
             || typeDeclaration.getDeclaredFieldDescriptors().stream()
                 .anyMatch(fieldDescriptor -> AstUtils.needsWasmJsExport(fieldDescriptor)));
   }
 
+  /** Returns true if this type defined in Wasm is exported to/visible in JS. */
+  public static boolean isWasmJsExportedType(TypeDeclaration typeDeclaration) {
+    return findSuperTypeWithWasmJsExportsIncludingSelf(typeDeclaration) != null;
+  }
+
+  /** Returns true if this type defined in Wasm is exported to/visible in JS. */
+  public static boolean isWasmJsExportedType(TypeDescriptor typeDescriptor) {
+    return typeDescriptor instanceof DeclaredTypeDescriptor dtd
+        && findSuperTypeWithWasmJsExportsIncludingSelf(dtd) != null;
+  }
+
   /**
    * Returns the first supertype of the given type that has a JS prototype in Wasm, including the
    * type itself.
    *
    * <p>If no supertype has a JS prototype, returns null.
    */
   @Nullable
-  public static DeclaredTypeDescriptor findSuperTypeWithWasmJsPrototypeIncludingSelf(
+  public static DeclaredTypeDescriptor findSuperTypeWithWasmJsExportsIncludingSelf(
       TypeDeclaration typeDeclaration) {
-    return findSuperTypeWithWasmJsPrototypeIncludingSelf(typeDeclaration.toDescriptor());
+    return findSuperTypeWithWasmJsExportsIncludingSelf(typeDeclaration.toDescriptor());
   }
 
   /**
@@ -1367,14 +1382,13 @@ public static DeclaredTypeDescriptor findSuperTypeWithWasmJsPrototypeIncludingSe
    * <p>If no supertype has a JS prototype, returns null.
    */
   @Nullable
-  public static DeclaredTypeDescriptor findSuperTypeWithWasmJsPrototypeIncludingSelf(
+  public static DeclaredTypeDescriptor findSuperTypeWithWasmJsExportsIncludingSelf(
       @Nullable DeclaredTypeDescriptor typeDescriptor) {
-    DeclaredTypeDescriptor superTypeWithJsPrototype = typeDescriptor;
-    while (superTypeWithJsPrototype != null) {
-      if (hasWasmJsPrototype(superTypeWithJsPrototype.getTypeDeclaration())) {
-        return superTypeWithJsPrototype;
+    while (typeDescriptor != null) {
+      if (declaresWasmJsExports(typeDescriptor.getTypeDeclaration())) {
+        return typeDescriptor;
       }
-      superTypeWithJsPrototype = superTypeWithJsPrototype.getSuperTypeDescriptor();
+      typeDescriptor = typeDescriptor.getSuperTypeDescriptor();
     }
     return null;
   }

transpiler/java/com/google/j2cl/transpiler/backend/wasm/JsExternsGenerator.java

@@ -15,7 +15,7 @@
  */
 package com.google.j2cl.transpiler.backend.wasm;
 
-import static com.google.j2cl.transpiler.ast.AstUtils.findSuperTypeWithWasmJsPrototypeIncludingSelf;
+import static com.google.j2cl.transpiler.ast.AstUtils.isWasmJsExportedType;
 
 import com.google.j2cl.common.OutputUtils.Output;
 import com.google.j2cl.transpiler.ast.AstUtils;
@@ -74,10 +74,8 @@ private boolean shouldGenerateExtern(DeclaredTypeDescriptor typeDescriptor) {
       return false;
     }
 
-    // Generate externs if the type has a JS prototype or if the type has a supertype with a JS
-    // prototype. In practice, because j.l.Object has a JS prototype, this nearly all types (some
-    // exclusions such as interfaces and native types)
-    return findSuperTypeWithWasmJsPrototypeIncludingSelf(typeDescriptor) != null;
+    // Generate externs if this type or a supertype is visible to JS.
+    return isWasmJsExportedType(typeDescriptor);
   }
 
   private void generateExtern(Type type) {

transpiler/java/com/google/j2cl/transpiler/backend/wasm/WasmConstructsGenerator.java

@@ -17,7 +17,7 @@
 
 import static com.google.common.base.Predicates.not;
 import static com.google.common.collect.ImmutableList.toImmutableList;
-import static com.google.j2cl.transpiler.ast.AstUtils.findSuperTypeWithWasmJsPrototypeIncludingSelf;
+import static com.google.j2cl.transpiler.ast.AstUtils.findSuperTypeWithWasmJsExportsIncludingSelf;
 import static com.google.j2cl.transpiler.ast.AstUtils.hasWasmJsPrototype;
 import static com.google.j2cl.transpiler.backend.wasm.WasmGenerationEnvironment.getWasmInfo;
 import static java.lang.String.format;
@@ -209,11 +209,11 @@ private void renderVtableStruct(Type type, Collection<MethodDescriptor> methods)
         /* descriptorClause= */ type.isInterface()
             ? null
             : format("describes %s", environment.getWasmTypeName(type.getTypeDescriptor())),
-        () -> renderVtableEntries(methods));
+        () -> renderVtableEntries(type, methods));
   }
 
-  private void renderVtableEntries(Collection<MethodDescriptor> methodDescriptors) {
-    if (environment.isCustomDescriptorsJsInteropEnabled()) {
+  private void renderVtableEntries(Type type, Collection<MethodDescriptor> methodDescriptors) {
+    if (environment.isCustomDescriptorsJsInteropEnabled() && !type.isInterface()) {
       // The first entry of the vtable is the JS prototype. This is used to export JsTypes to JS.
       // Because all types extend j.l.Object, they must have this first field to allow vtables to
       // extend each other.
@@ -596,9 +596,9 @@ private void emitVtableInitialization(
     builder.append(format("(struct.new %s", environment.getWasmVtableTypeName(implementedType)));
 
     builder.indent();
-    if (environment.isCustomDescriptorsJsInteropEnabled()) {
+    if (environment.isCustomDescriptorsJsInteropEnabled() && !implementedType.isInterface()) {
       // The first field of the vtable for JsTypes is the JS prototype.
-      var jsPrototypeType = findSuperTypeWithWasmJsPrototypeIncludingSelf(implementedType);
+      var jsPrototypeType = findSuperTypeWithWasmJsExportsIncludingSelf(implementedType);
       builder.newLine();
       if (jsPrototypeType != null) {
         builder.append(

transpiler/java/com/google/j2cl/transpiler/passes/JsInteropRestrictionsChecker.java

@@ -1745,10 +1745,7 @@ private boolean canCrossWasmJavaScriptBoundary(TypeDescriptor typeDescriptor) {
     return typeDescriptor.isPrimitive()
         || TypeDescriptors.isJavaLangString(typeDescriptor)
         || typeDescriptor.isNative()
-        || (checkWasmCustomDescriptorsJsInterop
-            && typeDescriptor instanceof DeclaredTypeDescriptor declaredTypeDescriptor
-            && AstUtils.findSuperTypeWithWasmJsPrototypeIncludingSelf(declaredTypeDescriptor)
-                != null);
+        || (checkWasmCustomDescriptorsJsInterop && AstUtils.isWasmJsExportedType(typeDescriptor));
   }
 
   private void checkMethodSignature(

transpiler/javatests/com/google/j2cl/readable/java/jsmethod/output_wasm/contents.wat.txt

@@ -99,7 +99,6 @@
 )
 (global $jsmethod.JsMethodExample.I.vtable@$jsmethod.JsMethodExample.Sub (ref $jsmethod.JsMethodExample.I.vtable)
  (struct.new $jsmethod.JsMethodExample.I.vtable
-  (ref.null extern)
   (ref.func $m_m__java_lang_String__void@jsmethod.JsMethodExample.Sub)
  )
 )
@@ -158,7 +157,6 @@
 )
 (global $jsmethod.JsMethodExample.InterfaceExposingJsMethods.vtable@$jsmethod.JsMethodExample.ExposesOverrideableJsMethod (ref $jsmethod.JsMethodExample.InterfaceExposingJsMethods.vtable)
  (struct.new $jsmethod.JsMethodExample.InterfaceExposingJsMethods.vtable
-  (ref.null extern)
   (ref.func $m_m__void@jsmethod.JsMethodExample.ExposesOverrideableJsMethod)
   (ref.func $m_n__void@jsmethod.JsMethodExample.SuperClassWithFinalMethod)
  )

transpiler/javatests/com/google/j2cl/readable/java/jsmethod/output_wasm/types.wat.txt

@@ -1,11 +1,9 @@
 
 (type $jsmethod.JsMethodExample.I.vtable (sub (struct
- (field $js_prototype (ref null extern))
  (field $m_m__java_lang_String__void (ref $function.m_m__java_lang_String__void))
  ))
 )
 (type $jsmethod.JsMethodExample.InterfaceWithMethod.vtable (sub (struct
- (field $js_prototype (ref null extern))
  (field $m_m__void (ref $function.m_m__void))
  (field $m_n__void (ref $function.m_n__void))
  ))
@@ -52,7 +50,6 @@
  ))
 )
 (type $jsmethod.JsMethodExample.InterfaceExposingJsMethods.vtable (sub $jsmethod.JsMethodExample.InterfaceWithMethod.vtable (struct
- (field $js_prototype (ref null extern))
  (field $m_m__void (ref $function.m_m__void))
  (field $m_n__void (ref $function.m_n__void))
  ))

transpiler/javatests/com/google/j2cl/readable/java/jsproperties/output_wasm/contents.wat.txt

@@ -89,7 +89,6 @@
 )
 (global $jsproperties.InterfaceWithDefaultJsProperties.vtable@$jsproperties.ImplementsInterfaceWithDefaultJsProperties (ref $jsproperties.InterfaceWithDefaultJsProperties.vtable)
  (struct.new $jsproperties.InterfaceWithDefaultJsProperties.vtable
-  (ref.null extern)
   (ref.func $m_getM__int@jsproperties.ImplementsInterfaceWithDefaultJsProperties)
   (ref.func $m_setM__int__void@jsproperties.ImplementsInterfaceWithDefaultJsProperties)
  )

transpiler/javatests/com/google/j2cl/readable/java/jsproperties/output_wasm/types.wat.txt

@@ -1,6 +1,5 @@
 
 (type $jsproperties.InterfaceWithDefaultJsProperties.vtable (sub (struct
- (field $js_prototype (ref null extern))
  (field $m_getM__int (ref $function.m_getM__int))
  (field $m_setM__int__void (ref $function.m_setM__int__void))
  ))

transpiler/javatests/com/google/j2cl/readable/java/jstype/output_wasm/types.wat.txt

@@ -1,10 +1,8 @@
 
 (type $jstype.SomeJsType.Star.$Overlay.vtable (sub (struct
- (field $js_prototype (ref null extern))
  ))
 )
 (type $jstype.SomeJsType.Wildcard.$Overlay.vtable (sub (struct
- (field $js_prototype (ref null extern))
  ))
 )
 (type $jstype.SomeJsType (sub $java.lang.Object (descriptor $jstype.SomeJsType.vtable) (struct