C++20: use view() instead of str() to avoid a copy, use starts_with (m…

…icrosoft#13218)

* Change files

* C++20: use view() instead of str() to avoid a copy, use starts_with

Signed-off-by: Nathanael Bracy <nate@bracy.dev>

* fix

* Apply changefile modifications from code review

Co-authored-by: Jon Thysell <thysell@gmail.com>

* Revert package.json

Signed-off-by: Nathanael Bracy <nate@bracy.dev>

---------

Signed-off-by: Nathanael Bracy <nate@bracy.dev>
Co-authored-by: Andrew Coates <30809111+acoates-ms@users.noreply.github.com>
Co-authored-by: Jon Thysell <thysell@gmail.com>

change/react-native-windows-f53a2b65-d364-49a5-978c-5d64e08c22ea.json

@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "Use view() instead of str(), starts_with() instead of _Starts_with()",
+  "packageName": "react-native-windows",
+  "email": "nate@bracy.dev",
+  "dependentChangeType": "patch"
+}

vnext/Microsoft.ReactNative/Utils/LocalBundleReader.cpp

@@ -59,11 +59,10 @@ std::future<std::string> LocalBundleReader::LoadBundleAsync(const std::wstring b
   winrt::Windows::Storage::StorageFile file{nullptr};
 
   // Supports "ms-appx://" or "ms-appdata://"
-  // TODO: Replace call to private string function with C++ 20 `starts_with`
-  if (bundleUri._Starts_with(L"ms-app")) {
+  if (bundleUri.starts_with(L"ms-app")) {
     winrt::Windows::Foundation::Uri uri(bundleUri);
     file = co_await winrt::Windows::Storage::StorageFile::GetFileFromApplicationUriAsync(uri);
-  } else if (bundleUri._Starts_with(L"resource://")) {
+  } else if (bundleUri.starts_with(L"resource://")) {
     winrt::Windows::Foundation::Uri uri(bundleUri);
     co_return GetBundleFromEmbeddedResource(uri);
   } else {

vnext/Shared/HermesSamplingProfiler.cpp

@@ -54,8 +54,7 @@ IAsyncOperation<winrt::hstring> getTraceFilePath() noexcept {
                  .count();
 
   os << hermesDataPath.c_str() << L"\\cpu_" << now << L".cpuprofile";
-  // TODO: Use C++ 20 `os.view()` to avoid a copy
-  co_return winrt::hstring(os.str());
+  co_return winrt::hstring(os.view());
 }
 
 } // namespace

vnext/Shared/OInstance.cpp

@@ -196,8 +196,7 @@ std::unique_ptr<const facebook::react::JSBigString> JsBigStringFromPath(
   return facebook::react::FileMappingBigString::fromPath(bundlePath);
 #else
   std::wstring bundlePath;
-  // TODO: Replace call to private string function with C++ 20 `starts_with`
-  if (devSettings->bundleRootPath._Starts_with("resource://")) {
+  if (devSettings->bundleRootPath.starts_with("resource://")) {
     auto uri = winrt::Windows::Foundation::Uri(
         winrt::to_hstring(devSettings->bundleRootPath), winrt::to_hstring(jsBundleRelativePath));
     bundlePath = uri.ToString();