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

dom/file/FileReader.cpp

@@ -88,6 +88,33 @@ public:
   }
 };
 
+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;
+  }
+
+  void
+  Abort()
+  {
+    mReader = nullptr;
+  }
+
+public:
+  RefPtr<FileReader> mReader;
+};
+
 void
 FileReader::RootResultArrayBuffer()
 {
@@ -446,7 +473,8 @@ FileReader::ReadFileContent(Blob& aBlob,
     }
   }
 
-  aRv = DoAsyncWait();
+  mAsyncWaitRunnable = new AsyncWaitRunnable(this);
+  aRv = NS_DispatchToCurrentThread(mAsyncWaitRunnable);
   if (NS_WARN_IF(aRv.Failed())) {
     FreeFileData();
     return;
@@ -454,6 +482,20 @@ FileReader::ReadFileContent(Blob& aBlob,
 
   //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));
 }
 
@@ -774,6 +816,11 @@ FileReader::Abort()
 
   ClearProgressEventTimer();
 
+  if (mAsyncWaitRunnable) {
+    mAsyncWaitRunnable->Abort();
+    mAsyncWaitRunnable = nullptr;
+  }
+
   mReadyState = DONE;
 
   // XXX The spec doesn't say this
@@ -783,7 +830,19 @@ FileReader::Abort()
   SetDOMStringToNull(mResult);
   mResultArrayBuffer = nullptr;
 
-  mAsyncStream = nullptr;
+  if (mAsyncStream) {
+    if (mBusyCount) {
+      // This will abort any pending reading. See nsIAsyncInputStream.idl.
+      mAsyncStream->AsyncWait(/* callback */ nullptr,
+                              /* aFlags*/ 0,
+                              /* aRequestedCount */ 0,
+                              mTarget);
+      DecreaseBusyCounter();
+      MOZ_ASSERT(mBusyCount == 0);
+    }
+    mAsyncStream = nullptr;
+  }
+
   mBlob = nullptr;
 
   //Clean up memory buffer
@@ -831,6 +890,11 @@ FileReader::Shutdown()
 {
   mReadyState = DONE;
 
+  if (mAsyncWaitRunnable) {
+    mAsyncWaitRunnable->Abort();
+    mAsyncWaitRunnable = nullptr;
+  }
+
   if (mAsyncStream) {
     mAsyncStream->Close();
     mAsyncStream = nullptr;

dom/file/FileReader.h

@@ -128,6 +128,8 @@ public:
   eDataFormat DataFormat() const { return mDataFormat; }
   const nsString& Result() const { return mResult; }
 
+  void InitialAsyncWait();
+
 private:
   virtual ~FileReader();
 
@@ -207,6 +209,10 @@ private:
   // 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

@@ -257,7 +257,7 @@ 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");
   });
 }
 
@@ -280,7 +280,7 @@ 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");
   });
 }
 
@@ -303,7 +303,7 @@ function test_readAsArrayBuffer(blob, text) {
 
     is(r.readyState, FileReader.LOADING, "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
-