codecs.StreamRecoder.writelines is broken

[JelleZijlstra]

BPO	33482
Nosy	@gvanrossum, @JelleZijlstra, @miss-islington
PRs	bpo-33482: fix codecs.StreamRecoder.writelines #6779 [3.6] bpo-33482: fix codecs.StreamRecoder.writelines (GH-6779) #13501 [3.7] bpo-33482: fix codecs.StreamRecoder.writelines (GH-6779) #13502

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2019-05-22.17:30:28.300>
created_at = <Date 2018-05-13.14:33:47.481>
labels = ['3.7', '3.8']
title = 'codecs.StreamRecoder.writelines is broken'
updated_at = <Date 2019-05-22.17:30:28.300>
user = 'https://github.com/JelleZijlstra'

bugs.python.org fields:

activity = <Date 2019-05-22.17:30:28.300>
actor = 'gvanrossum'
assignee = 'none'
closed = True
closed_date = <Date 2019-05-22.17:30:28.300>
closer = 'gvanrossum'
components = []
creation = <Date 2018-05-13.14:33:47.481>
creator = 'JelleZijlstra'
dependencies = []
files = []
hgrepos = []
issue_num = 33482
keywords = ['patch']
message_count = 4.0
messages = ['316465', '319343', '343200', '343216']
nosy_count = 3.0
nosy_names = ['gvanrossum', 'JelleZijlstra', 'miss-islington']
pr_nums = ['6779', '13501', '13502']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue33482'
versions = ['Python 3.6', 'Python 3.7', 'Python 3.8']

[JelleZijlstra]

codecs.StreamRecoder.writelines is implemented as:

    def writelines(self, list):

    data = ''.join(list)
    data, bytesdecoded = self.decode(data, self.errors)
    return self.writer.write(data)

It can't take a list of bytes because then the ''.join throws an error, and it can't take a list of str because self.decode takes bytes.

It looks like bytes are intended (self.write takes bytes), so I'll submit a simple PR to fix this.

[gvanrossum]

LGTM. Though sad there's no test that caught this. Could you add one.

[miss-islington]

New changeset b3be407 by Miss Islington (bot) (Jelle Zijlstra) in branch 'master':
bpo-33482: fix codecs.StreamRecoder.writelines (GH-6779)
b3be407

[miss-islington]

New changeset 81c5ec9 by Miss Islington (bot) (Jelle Zijlstra) in branch '3.7':
[3.7] bpo-33482: fix codecs.StreamRecoder.writelines (GH-6779) (GH-13502)
81c5ec9