request.post_body() can only be called once

[simonw]

This code here:

datasette/datasette/utils/asgi.py

Lines 127 to 135 in 452a587

	async def post_body(self):
	body = b""
	more_body = True
	while more_body:
	message = await self.receive()
	assert message["type"] == "http.request", message
	body += message.get("body", b"")
	more_body = message.get("more_body", False)
	return body

It consumes the messages, which means if you try to call it a second time you won't be able to get at the body.

This is efficient - we don't end up with a request object property with potentially megabytes of content that we never look at again - but it's inconvenient for cases like middleware or functions where we don't know if the body has been consumed yet or not.

Potential solution: set request._body the first time it is called, and return that on subsequent calls.

Potential optimization: only do this for bodies that are shorter than a certain threshold - maybe 1MB - and raise an exception if you attempt to call post_body() multiple times against one of those larger bodies.

I'm a bit nervous about that option though, since it could result in errors that don't show up in testing but do show up in production.