Preserve WinRT async error details in LocalBundleReader

vnext/Microsoft.ReactNative/Utils/LocalBundleReader.cpp

@@ -54,7 +54,29 @@ std::string GetBundleFromEmbeddedResource(const winrt::Windows::Foundation::Uri
   return std::string(start, start + size);
 }
 
-std::future<std::string> LocalBundleReader::LoadBundleAsync(const std::wstring bundleUri) {
+namespace {
+
+std::string BufferToString(const winrt::Windows::Storage::Streams::IBuffer &buffer) {
+  std::string result(buffer.Length(), '\0');
+  if (!result.empty()) {
+    auto reader = winrt::Windows::Storage::Streams::DataReader::FromBuffer(buffer);
+    reader.ReadBytes(winrt::array_view<uint8_t>{
+        reinterpret_cast<uint8_t *>(&result[0]), reinterpret_cast<uint8_t *>(&result[result.length()])});
+  }
+  return result;
+}
+
+winrt::Windows::Storage::Streams::IBuffer BytesToBuffer(const void *data, uint32_t size) {
+  winrt::Windows::Storage::Streams::DataWriter writer;
+  auto bytes = static_cast<const uint8_t *>(data);
+  writer.WriteBytes(winrt::array_view<const uint8_t>(bytes, bytes + size));
+  return writer.DetachBuffer();
+}
+
+} // namespace
+
+winrt::Windows::Foundation::IAsyncOperation<winrt::Windows::Storage::Streams::IBuffer>
+LocalBundleReader::LoadBundleAsync(const std::wstring bundleUri) {
   try {
     co_await winrt::resume_background();
 
@@ -66,41 +88,25 @@ std::future<std::string> LocalBundleReader::LoadBundleAsync(const std::wstring b
       file = co_await winrt::Windows::Storage::StorageFile::GetFileFromApplicationUriAsync(uri);
     } else if (bundleUri.starts_with(L"resource://")) {
       winrt::Windows::Foundation::Uri uri(bundleUri);
-      co_return GetBundleFromEmbeddedResource(uri);
+      auto bytes = GetBundleFromEmbeddedResource(uri);
+      co_return BytesToBuffer(bytes.data(), static_cast<uint32_t>(bytes.size()));
     } else {
       file = co_await winrt::Windows::Storage::StorageFile::GetFileFromPathAsync(bundleUri);
     }
 
-    // Read the buffer manually to avoid a Utf8 -> Utf16 -> Utf8 encoding
-    // roundtrip.
-    auto fileBuffer{co_await winrt::Windows::Storage::FileIO::ReadBufferAsync(file)};
-    auto dataReader{winrt::Windows::Storage::Streams::DataReader::FromBuffer(fileBuffer)};
-
-    // No need to use length + 1, STL guarantees that string storage is null-terminated.
-    std::string script(fileBuffer.Length(), '\0');
-
-    // Construct the array_view to slice into the first fileBuffer.Length bytes.
-    // DataReader.ReadBytes will read as many bytes as are present in the
-    // array_view. The backing string has fileBuffer.Length() + 1 bytes, without
-    // an explicit end it will read 1 byte to many and throw.
-    dataReader.ReadBytes(winrt::array_view<uint8_t>{
-        reinterpret_cast<uint8_t *>(&script[0]), reinterpret_cast<uint8_t *>(&script[script.length()])});
-    dataReader.Close();
-
-    co_return script;
+    co_return co_await winrt::Windows::Storage::FileIO::ReadBufferAsync(file);
   }
-  // RuntimeScheduler only handles std::exception or jsi::JSError
-  catch (winrt::hresult_error const &e) {
-    throw std::exception(winrt::to_string(e.message()).c_str());
+  catch (winrt::hresult_error const &) {
+    throw;
   }
 }
 
 std::string LocalBundleReader::LoadBundle(const std::wstring &bundlePath) {
-  return LoadBundleAsync(bundlePath).get();
+  return BufferToString(LoadBundleAsync(bundlePath).get());
 }
 
 StorageFileBigString::StorageFileBigString(const std::wstring &path) {
-  m_futureBuffer = LocalBundleReader::LoadBundleAsync(path);
+  m_pendingLoad = LocalBundleReader::LoadBundleAsync(path);
 }
 
 bool StorageFileBigString::isAscii() const {
@@ -118,8 +124,9 @@ size_t StorageFileBigString::size() const {
 }
 
 void StorageFileBigString::ensure() const {
-  if (m_string.empty()) {
-    m_string = m_futureBuffer.get();
+  if (m_pendingLoad) {
+    m_string = BufferToString(m_pendingLoad.get());
+    m_pendingLoad = nullptr;
   }
 }
 

vnext/Microsoft.ReactNative/Utils/LocalBundleReader.h

@@ -3,14 +3,16 @@
 
 #pragma once
 #include <cxxreact/JSBigString.h>
-#include <future>
+#include <winrt/Windows.Foundation.h>
+#include <winrt/Windows.Storage.Streams.h>
 #include <string>
 
 namespace Microsoft::ReactNative {
 
 class LocalBundleReader {
  public:
-  static std::future<std::string> LoadBundleAsync(const std::wstring bundlePath);
+  static winrt::Windows::Foundation::IAsyncOperation<winrt::Windows::Storage::Streams::IBuffer> LoadBundleAsync(
+      const std::wstring bundlePath);
   static std::string LoadBundle(const std::wstring &bundlePath);
 };
 
@@ -24,7 +26,7 @@ class StorageFileBigString : public facebook::react::JSBigString {
   void ensure() const;
 
  private:
-  mutable std::future<std::string> m_futureBuffer;
+  mutable winrt::Windows::Foundation::IAsyncOperation<winrt::Windows::Storage::Streams::IBuffer> m_pendingLoad;
   mutable std::string m_string;
 };