Improved errors returned from FileDataPipeProducer.

If a file read failed only MOJO_RESULT_ABORTED was returned.
This change does a best effort mapping of base::File::Error
values to the MojoResult value.

Bug: none
Change-Id: Iead2b3ce3b790960d5796ceeb15cfa1ff9c80741
Reviewed-on: https://chromium-review.googlesource.com/804615
Commit-Queue: Chris Mumford <cmumford@chromium.org>
Reviewed-by: Ken Rockot <rockot@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521543}

mojo/public/cpp/system/file_data_pipe_producer.cc

@@ -28,6 +28,27 @@ namespace {
 // 64 MB chunks whenever a producer is writable.
 constexpr uint32_t kDefaultMaxReadSize = 64 * 1024 * 1024;
 
+MojoResult FileErrorToMojoResult(base::File::Error error) {
+  switch (error) {
+    case base::File::FILE_OK:
+      return MOJO_RESULT_OK;
+    case base::File::FILE_ERROR_EXISTS:
+      return MOJO_RESULT_ALREADY_EXISTS;
+    case base::File::FILE_ERROR_NOT_FOUND:
+      return MOJO_RESULT_NOT_FOUND;
+    case base::File::FILE_ERROR_SECURITY:
+    case base::File::FILE_ERROR_ACCESS_DENIED:
+      return MOJO_RESULT_PERMISSION_DENIED;
+    case base::File::FILE_ERROR_TOO_MANY_OPENED:
+    case base::File::FILE_ERROR_NO_MEMORY:
+      return MOJO_RESULT_RESOURCE_EXHAUSTED;
+    case base::File::FILE_ERROR_ABORT:
+      return MOJO_RESULT_ABORTED;
+    default:
+      return MOJO_RESULT_UNKNOWN;
+  }
+}
+
 }  // namespace
 
 class FileDataPipeProducer::FileSequenceState
@@ -74,6 +95,10 @@ class FileDataPipeProducer::FileSequenceState
   ~FileSequenceState() = default;
 
   void StartFromFileOnFileSequence(base::File file, size_t max_bytes) {
+    if (file.error_details() != base::File::FILE_OK) {
+      Finish(FileErrorToMojoResult(file.error_details()));
+      return;
+    }
     file_ = std::move(file);
     max_bytes_ = max_bytes;
     TransferSomeBytes();
@@ -138,11 +163,18 @@ class FileDataPipeProducer::FileSequenceState
           std::min(static_cast<size_t>(size), max_bytes_remaining));
       int read_size = file_.ReadAtCurrentPos(static_cast<char*>(pipe_buffer),
                                              attempted_read_size);
+      base::File::Error read_error;
+      if (read_size < 0) {
+        read_error = base::File::GetLastFileError();
+        DCHECK_NE(base::File::FILE_OK, read_error);
+      } else {
+        read_error = base::File::FILE_OK;
+      }
       producer_handle_->EndWriteData(
           read_size >= 0 ? static_cast<uint32_t>(read_size) : 0);
 
       if (read_size < 0) {
-        Finish(MOJO_RESULT_ABORTED);
+        Finish(FileErrorToMojoResult(read_error));
         return;
       }
 

mojo/public/cpp/system/tests/file_data_pipe_producer_unittest.cc

@@ -180,6 +180,24 @@ TEST_F(FileDataPipeProducerTest, WriteFromFilePartial) {
   EXPECT_EQ(kTestString.substr(0, kBytesToWrite), reader.data());
 }
 
+TEST_F(FileDataPipeProducerTest, WriteFromInvalidFile) {
+  base::FilePath path(FILE_PATH_LITERAL("<nonexistent-file>"));
+  constexpr size_t kBytesToWrite = 7;
+
+  base::RunLoop loop;
+  DataPipe pipe(kBytesToWrite);
+  DataPipeReader reader(std::move(pipe.consumer_handle), kBytesToWrite,
+                        loop.QuitClosure());
+
+  base::File file(path, base::File::FLAG_OPEN | base::File::FLAG_READ);
+  WriteFromFileThenCloseWriter(
+      base::MakeUnique<FileDataPipeProducer>(std::move(pipe.producer_handle)),
+      std::move(file), kBytesToWrite);
+  loop.Run();
+
+  EXPECT_EQ(0UL, reader.data().size());
+}
+
 TEST_F(FileDataPipeProducerTest, WriteFromPath) {
   const std::string kTestStringFragment = "Hello, world!";
   constexpr size_t kNumRepetitions = 1000;