Error calling BaseHTTPRequestHandler.end_headers()

Bug report

Bug description:

If a call is made to BaseHTTPRequestHandler.end_headers() but no headers or response have been queued, an exception is raised exposing implementation details.

    class request_handler(BaseHTTPRequestHandler):
        def do_GET(self):
            self.end_headers()

Actual result

AttributeError("'request_handler' object has no attribute '_headers_buffer'")

Expected result:

pass

flush_headers has a guard to check if the buffer has been allocated which is missing from end_headers

if hasattr(self, '_headers_buffer'):

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Linked PRs

• gh-131718

Start by locating CPython's BaseHTTPRequestHandler.end_headers() and compare its handling with flush_headers(), especially the _headers_buffer guard described in the report. Done means calling end_headers() without queued headers or a response completes without exposing an AttributeError; check linked PR gh-131718 before starting.