Lexemes with only escaped characters cause a crash

[François Freitag]

Searching for Lexeme('&') passes the provided value through psql_escape, which returns None. When UTF8Dumper calls bytes(None, "utf-8"):

ERROR: test_quote_lexeme (postgres_tests.test_search.TestLexemes.test_quote_lexeme) (lexeme='&')
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/pdi/dev/django/tests/postgres_tests/test_search.py", line 886, in test_quote_lexeme
    self.assertEqual(quote_lexeme(lexeme), quoted)
                     ~~~~~~~~~~~~^^^^^^^^
  File "/home/pdi/dev/django/django/contrib/postgres/search.py", line 26, in quote_lexeme
    return UTF8Dumper(str).quote(psql_escape(value)).decode()
           ~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^
  File "/home/pdi/dev/django/.venv/lib/python3.14/site-packages/psycopg/adapt.py", line 59, in quote
    if (value := self.dump(obj)) is None:
                 ~~~~~~~~~^^^^^
  File "/home/pdi/dev/django/django/contrib/postgres/search.py", line 23, in dump
    return bytes(obj, "utf-8")
TypeError: encoding without a string argument

See the attached patch to reproduce in the django test suite.

Lexeme is documented as:

Lexeme objects allow search operators to be safely used with strings from an untrusted source. The content of each lexeme is escaped so that any operators that may exist in the string itself will not be interpreted.

[Jacob Walls]

Thanks for the report! Appears to only affect the psycopg3 path. Would you like to submit a PR?