Add asynchronous TextReader/TextWriter APIs

[Tarmil]

It would be useful to be able to read XML, JSON or CSV from a TextReader and write it to a TextWriter asynchronously. Especially now that ASP.NET Core 3.0 is disabling synchronous I/O on requests and responses by default. This would mean an AsyncLoad(TextReader) and AsyncWriteTo(TextWriter) method on each of these providers.

[github-actions]

🤖 This is an automated response from Repo Assist.

Thanks for this request! A quick note on the current state and design considerations:

What exists today

• CsvFile.Load(TextReader) and JsonValue.Load(TextReader) are available for synchronous parsing from a TextReader.
• AsyncLoad(string uri) exists for async loading from a URL or file path.
• There is no AsyncLoad(TextReader) or AsyncLoad(Stream) overload today.

Why it's non-trivial to add

The underlying parsers (CSV and JSON) call TextReader.ReadLine() / reader.Read() synchronously in tight loops. Adding a genuinely async AsyncLoad(TextReader) that calls ReadLineAsync() / ReadBlockAsync() internally would require significant refactoring of the parser internals.

A "fake async" wrapper that just does async { return Load(reader) } wouldn't help with ASP.NET Core's sync-I/O restriction, since it would still block a thread pool thread on I/O.

Recommended workaround today

Read the stream into memory asynchronously first, then parse synchronously:

// For CSV
let! text = reader.ReadToEndAsync() |> Async.AwaitTask
let csv = CsvFile.Parse(text)

// For JSON
let! text = reader.ReadToEndAsync() |> Async.AwaitTask
let json = JsonValue.Parse(text)

This is actually the safest approach for most payloads — it avoids holding a stream open while doing incremental parsing.

Contributions welcome! If someone wants to implement true async parsing (rewriting the parsers to use TextReader.ReadLineAsync()), that would be a valuable addition. The CSV parser in CsvFile.fs and JSON parser in JsonValue.fs would be the main starting points.

Generated by Repo Assist

To install this workflow, run gh aw add githubnext/agentics/workflows/repo-assist.md@b87234850bf9664d198f28a02df0f937d0447295. View source at https://github.com/githubnext/agentics/tree/b87234850bf9664d198f28a02df0f937d0447295/workflows/repo-assist.md.

[dsyme]

That's a good workaround