Bug 1682632 - part1.1: WebExtensionStub extended attribute in WebIDL generator. r=peterv,mixedpuppy

Define a new WebExtensionStub extended attribute in the WebIDL generator
to be used in the WebExtensions API WebIDL definitions.

Depends on D70372

Differential Revision: https://phabricator.services.mozilla.com/D84681

dom/bindings/Codegen.py

@@ -9485,12 +9485,22 @@ class CGPerSignatureCall(CGThing):
             # Callee expects a quoted string for the context if
             # there's a context.
             context = '"%s"' % context
+
+            if idlNode.isMethod() and idlNode.getExtendedAttribute("WebExtensionStub"):
+                [
+                    nativeMethodName,
+                    argsPre,
+                    args,
+                ] = self.processWebExtensionStubAttribute(idlNode, cgThings)
+            else:
+                args = self.getArguments()
+
             cgThings.append(
                 CGCallGenerator(
                     self.needsErrorResult(),
                     needsCallerType(idlNode),
                     isChromeOnly(idlNode),
-                    self.getArguments(),
+                    args,
                     argsPre,
                     returnType,
                     self.extendedAttributes,
@@ -9547,6 +9557,95 @@ class CGPerSignatureCall(CGThing):
     def getArguments(self):
         return [(a, "arg" + str(i)) for i, a in enumerate(self.arguments)]
 
+    def processWebExtensionStubAttribute(self, idlNode, cgThings):
+        nativeMethodName = "CallWebExtMethod"
+        stubNameSuffix = idlNode.getExtendedAttribute("WebExtensionStub")
+        if isinstance(stubNameSuffix, list):
+            nativeMethodName += stubNameSuffix[0]
+
+        argsLength = len(self.getArguments())
+        singleVariadicArg = argsLength == 1 and self.getArguments()[0][0].variadic
+
+        # If the method signature does only include a single variadic arguments,
+        # then `arg0` is already a Sequence of JS values and we can pass that
+        # to the WebExtensions Stub method as is.
+        if singleVariadicArg:
+            argsPre = [
+                "cx",
+                'u"%s"_ns' % idlNode.identifier.name,
+                "Constify(%s)" % "arg0",
+            ]
+            args = []
+            return [nativeMethodName, argsPre, args]
+
+        argsPre = [
+            "cx",
+            'u"%s"_ns' % idlNode.identifier.name,
+            "Constify(%s)" % "args_sequence",
+        ]
+        args = []
+
+        # Determine the maximum number of elements of the js values sequence argument,
+        # skipping the last optional callback argument if any:
+        #
+        # if this WebExtensions API method does expect a last optional callback argument,
+        # then it is the callback parameter supported for chrome-compatibility
+        # reasons, and we want it as a separate argument passed to the WebExtension
+        # stub method and skip it from the js values sequence including all other
+        # arguments.
+        maxArgsSequenceLen = argsLength
+        if argsLength > 0:
+            lastArg = self.getArguments()[argsLength - 1]
+            isCallback = lastArg[0].type.tag() == IDLType.Tags.callback
+            if isCallback and lastArg[0].optional:
+                argsPre.append(
+                    "MOZ_KnownLive(NonNullHelper(Constify(%s)))" % lastArg[1]
+                )
+                maxArgsSequenceLen = argsLength - 1
+
+        cgThings.append(
+            CGGeneric(
+                dedent(
+                    fill(
+                        """
+            // Collecting all args js values into the single sequence argument
+            // passed to the webextensions stub method.
+            //
+            // NOTE: The stub method will receive the original non-normalized js values,
+            // but those arguments will still be normalized on the main thread by the 
+            // WebExtensions API request handler using the same JSONSchema defnition
+            // used by the non-webIDL webextensions API bindings.
+            AutoSequence<JS::Value> args_sequence;
+            SequenceRooter<JS::Value> args_sequence_holder(cx, &args_sequence);
+
+            // maximum number of arguments expected by the WebExtensions API method
+            // excluding the last optional chrome-compatible callback argument (which
+            // is being passed to the stub method as a separate additional argument).
+            uint32_t maxArgsSequenceLen = ${maxArgsSequenceLen};
+
+            uint32_t sequenceArgsLen = args.length() <= maxArgsSequenceLen ?
+              args.length() : maxArgsSequenceLen;
+
+            if (sequenceArgsLen > 0) {
+              if (!args_sequence.SetCapacity(sequenceArgsLen, mozilla::fallible)) {
+                JS_ReportOutOfMemory(cx);
+                return false;
+              }
+              for (uint32_t argIdx = 0; argIdx < sequenceArgsLen; ++argIdx) {
+                // OK to do infallible append here, since we ensured capacity already.
+                JS::Value& slot = *args_sequence.AppendElement();
+                slot = args[argIdx];
+              }
+            }
+            """,
+                        maxArgsSequenceLen=maxArgsSequenceLen,
+                    )
+                )
+            )
+        )
+
+        return [nativeMethodName, argsPre, args]
+
     def needsErrorResult(self):
         return "needsErrorResult" in self.extendedAttributes
 

dom/bindings/parser/WebIDL.py

@@ -6394,6 +6394,7 @@ class IDLMethod(IDLInterfaceMember, IDLScope):
             or identifier == "StaticClassOverride"
             or identifier == "NonEnumerable"
             or identifier == "Unexposed"
+            or identifier == "WebExtensionStub"
         ):
             # Known attributes that we don't need to do anything with here
             pass