Use async ChangeToken.OnChange overload in KeyPerFileConfigurationProvider

[svick]

Uses the new async (Func<Task>) overload of ChangeToken.OnChange (see dotnet/runtime#69099) in KeyPerFileConfigurationProvider.

The reload callback previously blocked the file-watcher callback thread for the whole reload delay via Thread.Sleep(Source.ReloadDelay) (default 250 ms). It now awaits Task.Delay(...) instead, so no thread is blocked while waiting out the debounce delay before reloading:

_changeTokenRegistration = ChangeToken.OnChange(
    () => Source.FileProvider.Watch("*"),
    async () =>
    {
        await Task.Delay(Source.ReloadDelay).ConfigureAwait(false);
        Load(reload: true);
    });

The same change for FileConfigurationProvider is at dotnet/runtime#130492.

Test changes

Two reload tests asserted the reloaded configuration synchronously immediately after triggering a change, which only worked because the old Thread.Sleep ran the reload inline on the change-notification thread. With the non-blocking async reload, the reload now completes on a thread-pool thread, so these tests now await the config reload token before asserting — matching the existing RaiseChangeEventWhenReloadOnChangeIsTrue test:

• ReloadConfigWhenReloadOnChangeIsTrue
• NoFilesReloadWhenAddedFiles

Note

This PR description was generated by GitHub Copilot.

[Copilot]

Pull request overview

This PR updates the KeyPerFile configuration provider to use the async (Func<Task>) ChangeToken.OnChange overload so reload debouncing (ReloadDelay) no longer blocks the file-watcher callback thread, and adjusts related tests to await reload completion.

Changes:

• Switch KeyPerFileConfigurationProvider reload callback from Thread.Sleep to await Task.Delay(...) before reloading.
• Add a try/catch around Load(reload: true) in the change callback to avoid exceptions escaping the async callback.
• Update reload-related tests to be async, await the reload token, and apply timeouts.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/Configuration.KeyPerFile/src/KeyPerFileConfigurationProvider.cs	Uses async OnChange callback and Task.Delay for non-blocking debounce before reload.
src/Configuration.KeyPerFile/test/KeyPerFileTests.cs	Converts relevant tests to async and waits for the reload token before asserting.