Bug 1546603 - Don't finalize stream sources from JS if creating the stream object failed, r=arai.

Differential Revision: https://phabricator.services.mozilla.com/D28931

--HG--
extra : rebase_source : 558bd2bfdba22088906449c3388f25edc8c62786
extra : histedit_source : 643d9c253e5d00159c571651cf85e61956f1eca5

js/src/builtin/Stream.cpp

@@ -3467,6 +3467,28 @@ bool ReadableByteStreamController::constructor(JSContext* cx, unsigned argc,
   return false;
 }
 
+// Disconnect the source from a controller without calling finalize() on it,
+// unless this class is reset(). This ensures that finalize() will not be called
+// on the source if setting up the controller fails.
+class MOZ_RAII AutoClearUnderlyingSource {
+  Rooted<ReadableStreamController*> controller_;
+
+ public:
+  AutoClearUnderlyingSource(JSContext* cx, ReadableStreamController* controller)
+      : controller_(cx, controller) {}
+
+  ~AutoClearUnderlyingSource() {
+    if (controller_) {
+      ReadableStreamController::clearUnderlyingSource(
+          controller_, /* finalizeSource */ false);
+    }
+  }
+
+  void reset() {
+    controller_ = nullptr;
+  }
+};
+
 /**
  * Version of SetUpReadableByteStreamController that's specialized for handling
  * external, embedding-provided, underlying sources.
@@ -3481,6 +3503,8 @@ static MOZ_MUST_USE bool SetUpExternalReadableByteStreamController(
     return false;
   }
 
+  AutoClearUnderlyingSource autoClear(cx, controller);
+
   // Step 1: Assert: stream.[[readableStreamController]] is undefined.
   MOZ_ASSERT(!stream->hasController());
 
@@ -3556,6 +3580,7 @@ static MOZ_MUST_USE bool SetUpExternalReadableByteStreamController(
     return false;
   }
 
+  autoClear.reset();
   return true;
 }
 

js/src/builtin/Stream.h

@@ -317,9 +317,12 @@ class ReadableStreamController : public StreamController {
     addFlags(Flag_ExternalSource);
   }
   static void clearUnderlyingSource(
-      JS::Handle<ReadableStreamController*> controller) {
+      JS::Handle<ReadableStreamController*> controller,
+      bool finalizeSource = true) {
     if (controller->hasExternalSource()) {
-      controller->externalSource()->finalize();
+      if (finalizeSource) {
+        controller->externalSource()->finalize();
+      }
       controller->setFlags(controller->flags() & ~Flag_ExternalSource);
     }
     controller->setUnderlyingSource(JS::UndefinedHandleValue);