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Immutable module type can't be used as package in custom loader #83517
Description
| BPO | 39336 |
|---|---|
| Nosy | @brettcannon, @vstinner, @DinoV, @corona10 |
| PRs |
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 = 'https://github.com/DinoV'
closed_at = <Date 2020-01-23.00:57:27.184>
created_at = <Date 2020-01-14.21:33:31.500>
labels = ['interpreter-core', 'type-bug']
title = "Immutable module type can't be used as package in custom loader"
updated_at = <Date 2020-01-28.02:21:01.711>
user = 'https://github.com/DinoV'bugs.python.org fields:
activity = <Date 2020-01-28.02:21:01.711>
actor = 'vstinner'
assignee = 'dino.viehland'
closed = True
closed_date = <Date 2020-01-23.00:57:27.184>
closer = 'dino.viehland'
components = ['Interpreter Core']
creation = <Date 2020-01-14.21:33:31.500>
creator = 'dino.viehland'
dependencies = []
files = []
hgrepos = []
issue_num = 39336
keywords = ['patch']
message_count = 7.0
messages = ['360000', '360006', '360014', '360164', '360525', '360745', '360832']
nosy_count = 4.0
nosy_names = ['brett.cannon', 'vstinner', 'dino.viehland', 'corona10']
pr_nums = ['18006']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue39336'
versions = []
Activity
DinoV commentedon Jan 14, 2020
I'm trying to create a custom module type for a custom loader where the returned modules are immutable. But I'm running into an issue where the immutable module type can't be used as a module for a package. That's because the import machinery calls setattr to set the module as an attribute on it's parent in _boostrap.py
I'd be okay if for these immutable module types they simply didn't have their children packages published on them.
A simple simulation of this is a package which replaces its self with an object which doesn't support adding arbitrary attributes:
x/init.py:
import sys
sys.modules['x'] = MyMod()
x/y.py:
# Empty file
There's a few different options I could see on how this could be supported:
1) Simply handle the attribute error and allow things to continue
2) Add ability for the modules loader to perform the set, and fallback to setattr if one isn't available. Such as:
getattr(parent_module, 'add_child_module', setattr)(parent_module, name.rpartition('.')[2], module)
3) Add the ability for the module type to handle the setattr:
getattr(type(parent_module), 'add_child_module', fallback)(parent_module,
, name.rpartition('.')[2], module)
brettcannon commentedon Jan 14, 2020
So I think this is way too marginal a use-case to expand the API to let loaders inject themselves into the semantics of it.
I assume going with option 1 but raising an ImportWarning would be too noisy for your use-case? If not I'm totally fine with that solution.
DinoV commentedon Jan 14, 2020
I think the warning shouldn't be too bad. It looks like ImportWarnings are filtered by default already, and the extra overhead of raising a warning in this case probably is nothing compared to the actual work in loading the module.
corona10 commentedon Jan 17, 2020
I apologize for the noise caused by the wrong PR connection.
DinoV commentedon Jan 23, 2020
New changeset 9b6fec4 by Dino Viehland in branch 'master':
bpo-39336: Allow packages to not let their child modules be set on them (bpo-18006)
9b6fec4
vstinner commentedon Jan 27, 2020
test_unwritable_module() fails on AMD64 Fedora Stable Clang Installed 3.x: bpo-39459.
vstinner commentedon Jan 28, 2020
commit 2528a6c
Author: Dino Viehland <dinoviehland@gmail.com>
Date: Mon Jan 27 14:04:56 2020 -0800