Bug 1502403 - FileReader should dispatch loadstart asynchronously, r=smaug,ssengupta

Differential Revision: https://phabricator.services.mozilla.com/D78852

dom/file/FileReader.cpp

@@ -84,6 +84,28 @@ class MOZ_RAII FileReaderDecreaseBusyCounter {
   ~FileReaderDecreaseBusyCounter() { mFileReader->DecreaseBusyCounter(); }
 };
 
+class FileReader::AsyncWaitRunnable final : public CancelableRunnable {
+ public:
+  explicit AsyncWaitRunnable(FileReader* aReader)
+      : CancelableRunnable("FileReader::AsyncWaitRunnable"), mReader(aReader) {}
+
+  NS_IMETHOD
+  Run() override {
+    if (mReader) {
+      mReader->InitialAsyncWait();
+    }
+    return NS_OK;
+  }
+
+  nsresult Cancel() override {
+    mReader = nullptr;
+    return NS_OK;
+  }
+
+ public:
+  RefPtr<FileReader> mReader;
+};
+
 void FileReader::RootResultArrayBuffer() { mozilla::HoldJSObjects(this); }
 
 // FileReader constructors/initializers
@@ -156,7 +178,7 @@ void FileReader::GetResult(JSContext* aCx,
     return;
   }
 
-  if (mResult.IsVoid()) {
+  if (mReadyState != DONE || mResult.IsVoid()) {
     aResult.SetNull();
     return;
   }
@@ -400,7 +422,8 @@ void FileReader::ReadFileContent(Blob& aBlob, const nsAString& aCharset,
     }
   }
 
-  aRv = DoAsyncWait();
+  mAsyncWaitRunnable = new AsyncWaitRunnable(this);
+  aRv = NS_DispatchToCurrentThread(mAsyncWaitRunnable);
   if (NS_WARN_IF(aRv.Failed())) {
     FreeFileData();
     return;
@@ -408,6 +431,18 @@ void FileReader::ReadFileContent(Blob& aBlob, const nsAString& aCharset,
 
   // FileReader should be in loading state here
   mReadyState = LOADING;
+}
+
+void FileReader::InitialAsyncWait() {
+  mAsyncWaitRunnable = nullptr;
+
+  nsresult rv = DoAsyncWait();
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    mReadyState = EMPTY;
+    FreeFileData();
+    return;
+  }
+
   DispatchProgressEvent(NS_LITERAL_STRING(LOADSTART_STR));
 }
 
@@ -694,6 +729,11 @@ void FileReader::Abort() {
 
   ClearProgressEventTimer();
 
+  if (mAsyncWaitRunnable) {
+    mAsyncWaitRunnable->Cancel();
+    mAsyncWaitRunnable = nullptr;
+  }
+
   mReadyState = DONE;
 
   // XXX The spec doesn't say this
@@ -703,6 +743,20 @@ void FileReader::Abort() {
   SetDOMStringToNull(mResult);
   mResultArrayBuffer = nullptr;
 
+  // If we have the stream and the busy-count is not 0, it means that we are
+  // waiting for an OnInputStreamReady() call. Let's abort the current
+  // AsyncWait() calling it again with a nullptr callback. See
+  // nsIAsyncInputStream.idl.
+  if (mAsyncStream && mBusyCount) {
+    mAsyncStream->AsyncWait(/* callback */ nullptr,
+                            /* aFlags*/ 0,
+                            /* aRequestedCount */ 0, mTarget);
+    DecreaseBusyCounter();
+    MOZ_ASSERT(mBusyCount == 0);
+
+    mAsyncStream->Close();
+  }
+
   mAsyncStream = nullptr;
   mBlob = nullptr;
 
@@ -712,7 +766,7 @@ void FileReader::Abort() {
   // Dispatch the events
   DispatchProgressEvent(NS_LITERAL_STRING(ABORT_STR));
   DispatchProgressEvent(NS_LITERAL_STRING(LOADEND_STR));
-}
+}  // namespace dom
 
 nsresult FileReader::IncreaseBusyCounter() {
   if (mWeakWorkerRef && mBusyCount++ == 0) {
@@ -745,6 +799,11 @@ void FileReader::DecreaseBusyCounter() {
 void FileReader::Shutdown() {
   mReadyState = DONE;
 
+  if (mAsyncWaitRunnable) {
+    mAsyncWaitRunnable->Cancel();
+    mAsyncWaitRunnable = nullptr;
+  }
+
   if (mAsyncStream) {
     mAsyncStream->Close();
     mAsyncStream = nullptr;

dom/file/FileReader.h

@@ -117,6 +117,8 @@ class FileReader final : public DOMEventTargetHelper,
   eDataFormat DataFormat() const { return mDataFormat; }
   const nsString& Result() const { return mResult; }
 
+  void InitialAsyncWait();
+
  private:
   virtual ~FileReader();
 
@@ -191,6 +193,10 @@ class FileReader final : public DOMEventTargetHelper,
   // This value is set when the reading starts in order to keep the worker alive
   // during the process.
   RefPtr<StrongWorkerRef> mStrongWorkerRef;
+
+  // Runnable to start the reading asynchronous.
+  class AsyncWaitRunnable;
+  RefPtr<AsyncWaitRunnable> mAsyncWaitRunnable;
 };
 
 NS_DEFINE_STATIC_IID_ACCESSOR(FileReader, FILEREADER_ID)

dom/file/tests/common_fileReader.js

@@ -344,7 +344,7 @@ function test_readAsText(blob, text) {
 
     is(r.readyState, FileReader.LOADING, "correct loading text readyState");
     is(onloadHasRun, false, "text loading must be async");
-    is(onloadStartHasRun, true, "text loadstart should fire sync");
+    is(onloadStartHasRun, false, "text loadstart should fire async");
   });
 }
 
@@ -378,7 +378,7 @@ function test_readAsBinaryString(blob, text) {
 
     is(r.readyState, FileReader.LOADING, "correct loading binary readyState");
     is(onloadHasRun, false, "binary loading must be async");
-    is(onloadStartHasRun, true, "binary loadstart should fire sync");
+    is(onloadStartHasRun, false, "binary loadstart should fire async");
   });
 }
 
@@ -419,7 +419,7 @@ function test_readAsArrayBuffer(blob, text) {
       "correct loading arrayBuffer readyState"
     );
     is(onloadHasRun, false, "arrayBuffer loading must be async");
-    is(onloadStartHasRun, true, "arrayBuffer loadstart should fire sync");
+    is(onloadStartHasRun, false, "arrayBuffer loadstart should fire sync");
   });
 }
 

testing/web-platform/meta/FileAPI/reading-data-section/filereader_abort.html.ini

@@ -1,4 +0,0 @@
-[filereader_abort.html]
-  [Aborting after read]
-    expected: FAIL
-

testing/web-platform/meta/FileAPI/reading-data-section/filereader_events.any.js.ini

@@ -1,15 +0,0 @@
-[filereader_events.any.html]
-  [events are dispatched in the correct order for a non-empty blob]
-    expected: FAIL
-
-  [events are dispatched in the correct order for an empty blob]
-    expected: FAIL
-
-
-[filereader_events.any.worker.html]
-  [events are dispatched in the correct order for a non-empty blob]
-    expected: FAIL
-
-  [events are dispatched in the correct order for an empty blob]
-    expected: FAIL
-

testing/web-platform/meta/FileAPI/reading-data-section/filereader_result.html.ini

@@ -1,16 +0,0 @@
-[filereader_result.html]
-  [result is null during "loadstart" event for readAsBinaryString]
-    expected: FAIL
-
-  [result is null during "loadstart" event for readAsDataURL]
-    expected: FAIL
-
-  [result is null during "progress" event for readAsBinaryString]
-    expected: FAIL
-
-  [result is null during "loadstart" event for readAsArrayBuffer]
-    expected: FAIL
-
-  [result is null during "loadstart" event for readAsText]
-    expected: FAIL
-