Bug 1580014. Don't force methods into the "can throw any exception" bucket just because they always return a new JS object. r=peterv

Instead, mark them as "can OOM", since we have that concept now.

Differential Revision: https://phabricator.services.mozilla.com/D45251

--HG--
extra : moz-landing-system : lando

dom/bindings/Configuration.py

@@ -286,8 +286,6 @@ class NoSuchDescriptorError(TypeError):
 
 def methodReturnsJSObject(method):
     assert method.isMethod()
-    if method.returnsPromise():
-        return True
 
     for signature in method.signatures():
         returnType = signature[0]
@@ -656,9 +654,11 @@ class Descriptor(DescriptorProvider):
         if member.isMethod():
             # JSObject-returning [NewObject] methods must be fallible,
             # since they have to (fallibly) allocate the new JSObject.
-            if (member.getExtendedAttribute("NewObject") and
-                methodReturnsJSObject(member)):
-                throws = True
+            if member.getExtendedAttribute("NewObject"):
+                if member.returnsPromise():
+                    throws = True
+                elif methodReturnsJSObject(member):
+                    canOOM = True
             attrs = self.extendedAttributes['all'].get(name, [])
             maybeAppendInfallibleToAttrs(attrs, throws)
             maybeAppendCanOOMToAttrs(attrs, canOOM)

dom/encoding/TextEncoder.cpp

@@ -15,12 +15,12 @@ namespace dom {
 void TextEncoder::Encode(JSContext* aCx, JS::Handle<JSObject*> aObj,
                          JS::Handle<JSString*> aString,
                          JS::MutableHandle<JSObject*> aRetval,
-                         ErrorResult& aRv) {
+                         OOMReporter& aRv) {
   CheckedInt<size_t> bufLen(JS::GetStringLength(aString));
   bufLen *= 3;  // from the contract for JS_EncodeStringToUTF8BufferPartial
   // Uint8Array::Create takes uint32_t as the length.
   if (!bufLen.isValid() || bufLen.value() > UINT32_MAX) {
-    aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
+    aRv.ReportOOM();
     return;
   }
 
@@ -28,7 +28,7 @@ void TextEncoder::Encode(JSContext* aCx, JS::Handle<JSObject*> aObj,
   // is small.
   auto data = mozilla::MakeUniqueFallible<uint8_t[]>(bufLen.value());
   if (!data) {
-    aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
+    aRv.ReportOOM();
     return;
   }
 
@@ -37,7 +37,7 @@ void TextEncoder::Encode(JSContext* aCx, JS::Handle<JSObject*> aObj,
   auto maybe = JS_EncodeStringToUTF8BufferPartial(
       aCx, aString, AsWritableChars(MakeSpan(data.get(), bufLen.value())));
   if (!maybe) {
-    aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
+    aRv.ReportOOM();
     return;
   }
   Tie(read, written) = *maybe;
@@ -47,7 +47,7 @@ void TextEncoder::Encode(JSContext* aCx, JS::Handle<JSObject*> aObj,
   JSAutoRealm ar(aCx, aObj);
   JSObject* outView = Uint8Array::Create(aCx, written, data.get());
   if (!outView) {
-    aRv.Throw(NS_ERROR_OUT_OF_MEMORY);
+    aRv.ReportOOM();
     return;
   }
 

dom/encoding/TextEncoder.h

@@ -53,7 +53,7 @@ class TextEncoder final : public NonRefcountedDOMObject {
    */
   void Encode(JSContext* aCx, JS::Handle<JSObject*> aObj,
               JS::Handle<JSString*> aString,
-              JS::MutableHandle<JSObject*> aRetval, ErrorResult& aRv);
+              JS::MutableHandle<JSObject*> aRetval, OOMReporter& aRv);
 
   void EncodeInto(JSContext* aCx, JS::Handle<JSString*> aSrc,
                   const Uint8Array& aDst, TextEncoderEncodeIntoResult& aResult,

dom/webidl/Blob.webidl

@@ -31,7 +31,7 @@ interface Blob {
              optional DOMString contentType);
 
   // read from the Blob.
-  [NewObject] ReadableStream stream();
+  [NewObject, Throws] ReadableStream stream();
   [NewObject] Promise<USVString> text();
   [NewObject] Promise<ArrayBuffer> arrayBuffer();
 };