Add option to overwrite UploadFile impl

In our case we’re streaming in-flight uploaded files directly to MongoDB GridFS, so if we lose/crash some asgi worker process that is actually using the uploaded yet unprocessed file, a schedule job can detect this and resume operation. With SpooledTemporaryFile this is impossible because we can’t guarantee that resume job will land in the same container.

This all works well with Starlette, only drawback is that we need to monkey-patch UploadedFile class with our implementation, that sends chunks to Mongo’s GridFS.

Can Startlette have UploadedFile class configurable?

[zevisert]

Bump here from discussion https://github.com/encode/starlette/discussions/1934 - I can provide my own complex parsing, but there’s overhead that I can’t get rid of by having to read the spooled file from start to finish a second time. I hoped to be able to have starlette use a custom UploadFile subclass, as that would be a great place for us to add the logic we wanted.

[tomchristie]

Going to close this off for now with the same justification as https://github.com/encode/starlette/issues/849

Out of scope. If ya need more complex parsing than we currently provide, you need to do so within your own project.