Summary

QuerystringParser.finalize() doesn't emit field_end when the parser ends in FIELD_NAME state, silently dropping trailing bare field names.

Problem

When a querystring ends with a bare field name (no = sign), e.g. a=1&foo, the parser emits field_start and field_name for "foo" but finishes in FIELD_NAME state. The finalize() method only checks for FIELD_DATA:

def finalize(self) -> None:
    if self.state == QuerystringState.FIELD_DATA:
        self.callback("field_end")
    self.callback("end")

Since the state is FIELD_NAME, not FIELD_DATA, the field_end callback is never emitted. This causes unbalanced callbacks — the FormParser's on_field_end closure (which creates and delivers the field to the user) is never called, so the field is silently dropped.

Note: bare field names within a chunk (e.g. foo&a=1) are handled correctly — only trailing bare names at end-of-input are affected.

Fix

Check for both FIELD_DATA and FIELD_NAME states:

if self.state in (QuerystringState.FIELD_DATA, QuerystringState.FIELD_NAME):
    self.callback("field_end")