site.py reporting user site info even if ENABLE_USER_SITE=False

[bjmuld]

BPO	38238
Nosy	@tiran, @bjmuld
PRs	bpo-38238: site.py report user paths contingent on ENABLE_USER_SITE #16303

^{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 = None
created_at = <Date 2019-09-20.19:34:35.686>
labels = ['3.7', 'type-bug', 'library']
title = 'site.py reporting user site info even if ENABLE_USER_SITE=False'
updated_at = <Date 2019-09-23.10:58:24.685>
user = 'https://github.com/bjmuld'

bugs.python.org fields:

activity = <Date 2019-09-23.10:58:24.685>
actor = 'christian.heimes'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2019-09-20.19:34:35.686>
creator = 'bjmuld'
dependencies = []
files = []
hgrepos = []
issue_num = 38238
keywords = ['patch']
message_count = 2.0
messages = ['352884', '353008']
nosy_count = 2.0
nosy_names = ['christian.heimes', 'bjmuld']
pr_nums = ['16303']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue38238'
versions = ['Python 3.7']

Linked PRs

• gh-82419: improve doc for ENABLE_USER_SITE #121684
• gh-82419: Improve site docs to clarify user site-packages disabling #125083

[bjmuld]

site info is accessed externally via getusersitepackages() and getuserbase()... for example see "pip/_internal/locations.py"

If ENABLE_USER_SITE is set to "False," or otherwise disabled,
accesses to these methods should return '' or None (shouldn't they?).

Currently, I have ENABLE_USER_SITE globally disabled (by various means), but pip's call to getusersitepackages() is still returning "~/.local/lib/...".

This seems wrong. An alternative would be for external tools to manually import site.ENABLE_USER_SITE, but this seems incorrect.

[tiran]

getusersitepackages() and getuserbase() don't take ENABLE_USER_SITE into account. The function simply return the location of the user site-package directory independently of the value of ENABLE_USER_SITE. The check for ENABLE_USER_SITE and modification of sys.path occurs later. The design allows applications to get the hypothetical path for user site-packages independently from the ENABLE_USER_SITE flag.

The API is mature, old, and around since Python 2.6. We can't change it without breaking backwards compatibility.

[merwok]

I would review a patch to clarify the docs about this.

[pelson]

Just to say that, as a result of #107344, with Python 3.11+, even if you set the ENABLE_USER_SITE variable to False in site.py, it doesn't disable user site-packages (this is because Python no longer reads site.py at runtime, and rather falls back to the frozen version of site.py found at build-time).