Support user generated custom native JS classes.

pkg/compiler/lib/src/js_emitter/native_emitter.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart2js.js_emitter;
 
 class NativeEmitter {
 
   // TODO(floitsch): the native-emitter should not know about ClassBuilders.
   final Map<Element, full_js_emitter.ClassBuilder> cachedBuilders;
@@ skipping 116 matching lines @@
         needed = true;
       } else if (interceptorClassesNeededByConstants.contains(classElement)) {
         needed = true;
       } else if (classesModifiedByEmitRTISupport.contains(classElement)) {
         // TODO(9556): Remove this test when [emitRuntimeTypeSupport] no longer
         // adds information to a class prototype or constructor.
         needed = true;
       } else if (extensionPoints.containsKey(cls)) {
         needed = true;
       }
-      if (cls.isNative &&
-          native.nativeTagsForcedNonLeaf(classElement)) {
+      if (classElement.isJsInterop) {
+        needed = true;  // TODO(jacobr): we don't need all interop classes.

[Siggi Cherem (dart-lang), 2015/09/18 20:34:10]

what are your thoughts on determining what is needed?

- types that are allocated from Dart
- types returned from interop-functions (using trust-type-annotations, or using
metadata to declare whether the return type of functions includes a new type not
seen in the Dart code?

[Jacob, 2015/10/01 00:47:33]

types allocated from Dart isn't adequate
types returned from interop-functions could work as long as we also include
types returned from "as" checks. That still might not be sufficient. BTW, while
the JS interop classes are "needed" we don't really need to generate metadata
for them as at the end of the day all that matters is that the correct
interceptors are added to JavaScriptObject.

+      } else if (cls.isNative && native.nativeTagsForcedNonLeaf(classElement)) {
         needed = true;
         nonLeafClasses.add(cls);
       }
 
       if (needed || neededClasses.contains(cls)) {
         neededClasses.add(cls);
         neededClasses.add(cls.superclass);
         nonLeafClasses.add(cls.superclass);
       }
     }
 
     // Collect all the tags that map to each native class.
 
     Map<Class, Set<String>> leafTags = new Map<Class, Set<String>>();
     Map<Class, Set<String>> nonleafTags = new Map<Class, Set<String>>();
 
     for (Class cls in classes) {
       if (!cls.isNative) continue;
+      if (cls.element.isJsInterop) continue;
       List<String> nativeTags = native.nativeTagsOfClass(cls.element);
 
       if (nonLeafClasses.contains(cls) ||
           extensionPoints.containsKey(cls)) {
         nonleafTags
             .putIfAbsent(cls, () => new Set<String>())
             .addAll(nativeTags);
       } else {
         Class sufficingInterceptor = cls;
         while (!neededClasses.contains(sufficingInterceptor)) {
@@ skipping 120 matching lines @@
   List<jsAst.Statement> generateParameterStubStatements(
       FunctionElement member,
       bool isInterceptedMethod,
       jsAst.Name invocationName,
       List<jsAst.Parameter> stubParameters,
       List<jsAst.Expression> argumentsBuffer,
       int indexOfLastOptionalArgumentInParameters) {
     // The target JS function may check arguments.length so we need to
     // make sure not to pass any unspecified optional arguments to it.
     // For example, for the following Dart method:
-    //   foo([x, y, z]);
+    //   foo({x, y, z});
     // The call:
     //   foo(y: 1)
     // must be turned into a JS call to:
     //   foo(null, y).
 
     List<jsAst.Statement> statements = <jsAst.Statement>[];
     potentiallyConvertDartClosuresToJs(statements, member, stubParameters);
 
     String target;
     jsAst.Expression receiver;
     List<jsAst.Expression> arguments;
 
     assert(invariant(member, nativeMethods.contains(member)));
     // When calling a JS method, we call it with the native name, and only the
     // arguments up until the last one provided.
     target = member.fixedBackendName;
 
     if (isInterceptedMethod) {
       receiver = argumentsBuffer[0];
       arguments = argumentsBuffer.sublist(1,
           indexOfLastOptionalArgumentInParameters + 1);
     } else {
       // Native methods that are not intercepted must be static.
       assert(invariant(member, member.isStatic));
-      receiver = js('this');
       arguments = argumentsBuffer.sublist(0,
           indexOfLastOptionalArgumentInParameters + 1);
+      if (member.isJsInterop) {
+        // target is allowed to have the form foo.bar.baz for interop.
+        // TODO(jacobr): replace js(target) with a version that doesn't cache.
+        statements.add(
+            js.statement('return #(#)', [js(target), arguments]));

[Siggi Cherem (dart-lang), 2015/09/18 20:34:10]

style nit: might be nice to keep the statements.add at the end and only massage
the receiver part a bit. For example, could we turn the #.# into a js('#.#',
receiver, target) for the other cases?

[Jacob, 2015/10/01 00:47:33]

yeah this code was ugly. done.

+        return statements;
+      } else {
+        receiver = js('this');
+      }
     }
     statements.add(
         js.statement('return #.#(#)', [receiver, target, arguments]));
 
     return statements;
   }
 
   bool isSupertypeOfNativeClass(ClassElement element) {
     if (backend.classesMixedIntoInterceptedClasses.contains(element)) {
       return true;
     }
 
     return subtypes[element] != null;
   }
 
   bool requiresNativeIsCheck(Element element) {
     // TODO(sra): Remove this function.  It determines if a native type may
     // satisfy a check against [element], in which case an interceptor must be
     // used.  We should also use an interceptor if the check can't be satisfied
     // by a native class in case we get a native instance that tries to spoof
     // the type info.  i.e the criteria for whether or not to use an interceptor
     // is whether the receiver can be native, not the type of the test.
     if (element == null || !element.isClass) return false;
     ClassElement cls = element;
     if (Elements.isNativeOrExtendsNative(cls)) return true;
     return isSupertypeOfNativeClass(element);
   }
 }