FileSystemWritableFileStream write, seek and truncate description methods are not calling out the case of writable being locked

[youennf]

What is the issue with the File System Standard?

The spec currently says to acquire writer before writing.
Given acquiring the writer can throw, this should trigger a promise rejection as per my webIDL understanding.
This was not immediately clear from reading the spec so I wonder whether the spec should mention this somehow.

[annevk]

I think the non-normative description (aimed at web developers) should definitely mention it can be rejected.

The normative description I'm less clear on. As per https://infra.spec.whatwg.org/#algorithm-control-flow modern practice is to not state something can rethrow, but I do remember @domenic not being entirely comfortable with relying on the Web IDL layer for wrapping a thrown exception into a rejected promise return value. I don't think we ever settled on guidance for it though.