"distributions can disable the encodings package"

[pitrou]

BPO	13722
Nosy	@loewis, @terryjreedy, @amauryfa, @pitrou, @merwok

^{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 2012-01-18.21:39:29.779>
created_at = <Date 2012-01-06.20:32:22.157>
labels = ['interpreter-core']
title = '"distributions can disable the encodings package"'
updated_at = <Date 2012-01-18.21:39:29.778>
user = 'https://github.com/pitrou'

bugs.python.org fields:

activity = <Date 2012-01-18.21:39:29.778>
actor = 'pitrou'
assignee = 'none'
closed = True
closed_date = <Date 2012-01-18.21:39:29.779>
closer = 'pitrou'
components = ['Interpreter Core']
creation = <Date 2012-01-06.20:32:22.157>
creator = 'pitrou'
dependencies = []
files = []
hgrepos = []
issue_num = 13722
keywords = []
message_count = 5.0
messages = ['150767', '150777', '151220', '151290', '151569']
nosy_count = 6.0
nosy_names = ['loewis', 'terry.reedy', 'amaury.forgeotdarc', 'pitrou', 'eric.araujo', 'python-dev']
pr_nums = []
priority = 'low'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue13722'
versions = ['Python 3.3']

[pitrou]

In _PyCodecRegistry_Init() (in Python/codecs.c), it is attempted to import the encodings module (so that the default search function gets registered) and failures get ignored following the same reasoning:

        /* Ignore ImportErrors... this is done so that
           distributions can disable the encodings package. Note
           that other errors are not masked, e.g. SystemErrors
           raised to inform the user of an error in the Python
           configuration are still reported back to the user. */

However, it is unlikely for Python 3 to start up at all without an encodings package (we needs some codecs to initialize stdio). Also, I'm not sure what the point would be. Distributions can simply distribute a dummy encodings module if they really want to disable the default encodings.
Not silencing the error would probably make it easier to diagnose early import issues.

[amauryfa]

Agreed. This behavior probably comes from the times when unicode was an optional feature.

[terryjreedy]

Those lines were whitespace reformed by Antoine in 61466/61463.
They previously came from 28325 which fixed bpo-663074 (2003).
I do not see any discussion in that issue of making the import optional.
I suspect there is no test of Python working with no encodings ;-)

Just for fun, I commented out the import and error checks. There is an error message during the build about python_d.exe not working and python_d.exe crashes (ungracefully) on explicit startup, as you expected. I presume the patch is to delete the entire block added in 28325:
        if (PyErr_ExceptionMatches(PyExc_ImportError)) {
            /* Ignore ImportErrors... this is done so that
               distributions can disable the encodings package. Note
               that other errors are not masked, e.g. SystemErrors
               raised to inform the user of an error in the Python
               configuration are still reported back to the user. */
            PyErr_Clear();
            return 0;

Only in 3.3 or further back? I can do it if you like.

[pitrou]

Actually, that code is from bc861add5d71.
But the error was also muted in the initial checkin in d0e06efb3165.
In any case, the silencing should be removed, both in 3.2 and 3.3 IMO.

[python-dev]

New changeset 46b245f03f54 by Antoine Pitrou in branch '3.2':
Issue bpo-13722: Avoid silencing ImportErrors when initializing the codecs registry.
http://hg.python.org/cpython/rev/46b245f03f54

New changeset f55529aa023d by Antoine Pitrou in branch 'default':
Issue bpo-13722: Avoid silencing ImportErrors when initializing the codecs registry.
http://hg.python.org/cpython/rev/f55529aa023d