email.message_from_bytes not working on BytesIO() object

[cd311]

BPO	44870
Nosy	@warsaw, @ericvsmith, @bitdancer

^{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 2021-08-09.13:11:33.727>
created_at = <Date 2021-08-09.11:49:52.449>
labels = ['invalid', 'type-bug', '3.8', 'expert-email']
title = 'email.message_from_bytes not working on BytesIO() object'
updated_at = <Date 2021-08-09.13:11:33.725>
user = 'https://bugs.python.org/cd311'

bugs.python.org fields:

activity = <Date 2021-08-09.13:11:33.725>
actor = 'eric.smith'
assignee = 'none'
closed = True
closed_date = <Date 2021-08-09.13:11:33.727>
closer = 'eric.smith'
components = ['email']
creation = <Date 2021-08-09.11:49:52.449>
creator = 'cd311'
dependencies = []
files = []
hgrepos = []
issue_num = 44870
keywords = []
message_count = 2.0
messages = ['399259', '399262']
nosy_count = 4.0
nosy_names = ['barry', 'eric.smith', 'r.david.murray', 'cd311']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue44870'
versions = ['Python 3.8']

[cd311]

Hi,

the following minimal working example of the problem

from io import BytesIO
from os import read
import email

fp = BytesIO()

with open('mail.eml', 'rb') as f:
    filecontent = f.read()
    print("type(filecontent)= ", type(filecontent))
    fp.write(filecontent)

mailobj = email.message_from_bytes(fp)

produces the following exception

$ python testparser.py 
type(filecontent)=  <class 'bytes'>
Traceback (most recent call last):
  File "testparser.py", line 16, in <module>
    mailobj = email.message_from_bytes(fp)
  File "/usr/lib/python3.8/email/__init__.py", line 46, in message_from_bytes
    return BytesParser(*args, **kws).parsebytes(s)
  File "/usr/lib/python3.8/email/parser.py", line 122, in parsebytes
    text = text.decode('ASCII', errors='surrogateescape')
AttributeError: '_io.BytesIO' object has no attribute 'decode'

This is a python 3.8.10 on an Ubuntu 20.04 LTS installed from the packages.

The documentation for message_from_bytes https://docs.python.org/3.10/library/email.parser.html#email.message_from_bytes mentions bytes-like objects which links to https://docs.python.org/3.10/glossary.html#term-bytes-like-object and references object of type byte.

Shouldn't this work with BytesIO()? A'm I missing something?

with regards
Christian

[ericvsmith]

Use filecontent.getvalue(): https://docs.python.org/3/library/io.html#io.BytesIO.getvalue