Bug 963388. Add support for nullable dictionary return values in callbacks and js-implemented bindings. r=peterv

dom/bindings/Codegen.py

@@ -3844,12 +3844,15 @@ for (uint32_t i = 0; i < length; ++i) {
 
     if type.isDictionary():
         # There are no nullable dictionaries
-        assert not type.nullable()
+        assert not type.nullable() or isCallbackReturnValue
         # All optional dictionaries always have default values, so we
         # should be able to assume not isOptional here.
         assert not isOptional
+        # In the callback return value case we never have to worry
+        # about a default value; we always have a value.
+        assert not isCallbackReturnValue or defaultValue is None
 
-        typeName = CGDictionary.makeDictionaryName(type.inner)
+        typeName = CGDictionary.makeDictionaryName(type.unroll().inner)
         if not isMember and not isCallbackReturnValue:
             # Since we're not a member and not nullable or optional, no one will
             # see our real type, so we can do the fast version of the dictionary
@@ -3883,11 +3886,21 @@ for (uint32_t i = 0; i < length; ++i) {
         else:
             template = ""
 
-        template += ('if (!${declName}.Init(cx, %s, "%s")) {\n'
+        dictLoc = "${declName}"
+        if type.nullable():
+            dictLoc += ".SetValue()"
+
+        template += ('if (!%s.Init(cx, %s, "%s")) {\n'
                      "%s\n"
-                     "}" % (val, firstCap(sourceDescription),
+                     "}" % (dictLoc, val, firstCap(sourceDescription),
                             exceptionCodeIndented.define()))
 
+        if type.nullable():
+            declType = CGTemplatedType("Nullable", declType)
+            template = CGIfElseWrapper("${val}.isNullOrUndefined()",
+                                       CGGeneric("${declName}.SetNull();"),
+                                       CGGeneric(template)).define()
+
         # Dictionary arguments that might contain traceable things need to get
         # traced
         if not isMember and isCallbackReturnValue:

dom/bindings/test/TestCodeGen.webidl

@@ -29,6 +29,7 @@ callback interface TestCallbackInterface {
   sequence<TestCallbackInterface>? getNullableSequenceOfCallbackInterfaces();
   sequence<TestCallbackInterface?> getSequenceOfNullableCallbackInterfaces();
   sequence<TestCallbackInterface?>? getNullableSequenceOfNullableCallbackInterfaces();
+  Dict? getDictionary();
 };
 
 callback interface TestSingleOperationCallbackInterface {

dom/bindings/test/TestJSImplGen.webidl

@@ -469,21 +469,18 @@ interface TestJSImplInterface {
   void passDictionary(optional Dict x);
   [Cached, Pure]
   readonly attribute Dict readonlyDictionary;
-  // No support for nullable dictionary return values here yet
-  //  [Cached, Pure]
-  //  readonly attribute Dict? readonlyNullableDictionary;
+  [Cached, Pure]
+  readonly attribute Dict? readonlyNullableDictionary;
   [Cached, Pure]
   attribute Dict writableDictionary;
   [Cached, Pure, Frozen]
   readonly attribute Dict readonlyFrozenDictionary;
-  // No support for nullable dictionary return values here yet
-  //  [Cached, Pure, Frozen]
-  //  readonly attribute Dict? readonlyFrozenNullableDictionary;
+  [Cached, Pure, Frozen]
+  readonly attribute Dict? readonlyFrozenNullableDictionary;
   [Cached, Pure, Frozen]
   attribute Dict writableFrozenDictionary;
   Dict receiveDictionary();
-  // No support for nullable dictionary return values here yet
-  //  Dict? receiveNullableDictionary();
+  Dict? receiveNullableDictionary();
   void passOtherDictionary(optional GrandparentDict x);
   void passSequenceOfDictionaries(sequence<Dict> x);
   // No support for nullable dictionaries inside a sequence (nor should there be)