[issue31271] an assertion failure in io.TextIOWrapper.write

[Oren Milman]

New submission from Oren Milman:

currently, the following causes an assertion in Modules/_io/textio.c in
_io_TextIOWrapper_write_impl() to fail:
import codecs
import io

class BadEncoder():
    def encode(self, dummy):
        return 42
def _get_bad_encoder(dummy):
    return BadEncoder()

quopri = codecs.lookup("quopri")
quopri._is_text_encoding = True
quopri.incrementalencoder = _get_bad_encoder
t = io.TextIOWrapper(io.BytesIO(b'foo'), encoding="quopri")
t.write('bar')


this is because _io_TextIOWrapper_write_impl() doesn't check whether the value
returned by encoder's encode() is a bytes object.

(I would open a PR to fix that soon.)

----------
components: IO
messages: 300795
nosy: Oren Milman
priority: normal
severity: normal
status: open
title: an assertion failure in io.TextIOWrapper.write
type: crash
versions: Python 3.7

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue31271>
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