Support the "attrs" library #1698

The-Compiler · 2017-10-11T06:34:32Z

Many projects (Twisted, Hypothesis, pytest, my own, and probably more) started using attrs because it makes it much more pleasant to write data classes.

However, pylint doesn't understand attrs' handling of default values:

import attr

@attr.s
class Foo:

    d = attr.ib(attr.Factory(dict))

f = Foo()
f.d['answer'] = 42

outputs:

E:  9, 0: 'f.d' does not support item assignment (unsupported-assignment-operation)

Unfortunately, I can't find a way to turn this off selectively either, e.g. by adding Foo to ignored-classes.

The text was updated successfully, but these errors were encountered:

See pylint-dev/pylint#1698

PCManticore · 2017-10-12T07:54:26Z

This probably needs a brain plugin.
Also unfortunately ignored-classes can only be applied for a handful of errors, I think unsupported-assignment-operation doesn't fall in that category (ignored-classes is mostly for no-member and a bunch of others).

@hippo91

….6.0 Ashley Whetter (1): Public facing node documentation Bryce Guinta (1): Add transform for attr library to fix unsupported-assignment-operation false positives Claudiu Popa (40): Don't crash when getting the string representation of BadUnaryOperationMessage Don't raise DuplicateBaseError when classes at different locations are used The func form of namedtuples with keywords is now understood Dunder class at method level is now inferred as the class of the method Fix indentation Enums created with functional syntax are now iterable. Close pylint-dev/pylint#1546 Enums created with functional syntax are now iterable. Close pylint-dev/pylint#992 Enum's functional form know about __members__ Fix reconstruction of nodes for FormattedValue. Close pylint-dev/pylint#1582 Ignore the test on <Python3.6 namedtuple._replace expects the actual attributes to be replaced Disable stop-iteration-return until we'll drop support for python 2 The result of using object.__new__ as class decorator is correctly inferred as instance Support AnnAssign in Enum bodies. Close #442 Add brain tips for UUID.int Skip Uninferable inferred objects when inferring a Dict Check for both args and keyword arguments when extracting namedtuple's params. Close #450 Remove print statement Ignore directories found in blacklist __package__ is accessible in every module. Close pylint-dev/pylint#1693 Fix lint warnings lint the current directory, not the installed one Fix the remaining lint errors Run the local tests, not the installed ones, and strip the local path for coveralls Add ChangeLog entry Remove most of the copyright notices, since this file was written completely by @hippo91 Add ChangeLog entries for @hippo91 changes astroid's master is 1.6 Add pypy support for Python 3.3 in tox Revert "Add pypy support for Python 3.3 in tox" Remove file_stream since it was slated for removal for 1.6 Fix lint When verifying duplicates classes in MRO, ignore on-the-fly generated classes Make Unknown a rhs assignable node Make attr.ib attributes instances of Unknown, not of Attribute Only mock attr.ib attributes Remove unreachable code Filter non-inferables nodes when inferring binary operations Add new release instructions as for pylint Add the release date Hugo (4): Update classifiers (#453) Mark failing test as expected failure (#455) Drop support for EOL Python 3.3 Update version comparisons after review Michał Masłowski (1): Catch _NonDeducibleTypeHierarchy in inference._infer_augassign (#443) hippo91 (8): Expose more objects in numpy brain tip Introduction of numpy.core.umath functions signatures inside numpy brain + add of a dedicated unit test Introduction of numpy.random.mtrand functions signatures inside numpy brain + add of a dedicated unit test Add of a class that wrapps the call to unittest.subTest method to handle different versions of python Add of encoding utf-8 declaration Deletion of old numpy test (replaced by a dedicated class) Add of copyright and simplification of the mock to try to pass python3.3 CI Add of decorator to skip the tests if numy module is not present ioanatia (1): Fix finder for namespace packages (#440) mathieui (1): Add brain_curses.py for curses attributes defined at runtime (#456) Łukasz Rogalski (1): Improve understanding of collections.deque (#441) 2017-12-15 -- 1.6.0 * When verifying duplicates classes in MRO, ignore on-the-fly generated classes Close pylint-dev/pylint#1706 * Add brain tip for attrs library to prevent unsupported-assignment-operation false positives Close pylint-dev/pylint#1698 * file_stream was removed, since it was deprecated for three releases Instead one should use the .stream() method. * Vast improvements to numpy support (NEWS truncated at 15 lines)

tedbrandston · 2018-01-02T17:09:33Z

So is this a thing where we should just be waiting for the next release of pylint? Or is there something we can do to get this working right now?

Thanks!

The-Compiler · 2018-01-02T18:11:37Z

It's part of astroid 1.6.0 which already has been released.

zadamah · 2018-01-12T16:42:30Z

astroid 1.6.0 still reports an equivalent error if attr.s is given parameters, slightly modifying @The-Compiler example :

import attr

@attr.s(slots=True, cmp=True)
class Foo(object):
    d = attr.ib(attr.Factory(dict))

f = Foo()
f.d['answer'] = 42

outputs now :

E:  8, 0: 'f.d' does not support item assignment (unsupported-assignment-operation)

The predicate is_decorated_with_attrs (from astroid.brain.brain_attrs) is only True for decorators with no parameters, otherwise no transform is applied

I don't know enough about astroid (first day I read this part of the code) to propose a good way of handling this case, so if someone can help

And thank you all, this thread was a great read

dfee · 2018-08-01T01:15:49Z

Why is this closed? It's not supported, at least not on:
• astroid 2.0.0.dev4,
• pylint 2.0.0,
• attrs 18.1.0

zadamah · 2018-08-01T08:31:13Z

I think that that attr decorators with no arguments are supported
My pull request for the case with arguments was merged to master but until recently it did not make its way to a release. @The-Compiler can you help us on this ?

PCManticore · 2018-08-01T08:39:24Z

Folks, please open separate issues. Some attrs support landed in pylint but we cannot support everything out of the box unless we have separate issues for each particular thing that is not working. Also do take in account that we're all volunteers and we might not use attrs on a daily basis so there's a chance that we might not know what needs to be supported. Another thing is that asking why is this closed is usually not helpful, as most of the time we close issues either because there is no plan to fix them or (some partial) support for that particular feature landed already in the project.

The-Compiler · 2018-08-01T08:50:39Z

@zadamah I don't understand what you want me to help with? It looks like with pylint-dev/astroid#479 this should work, and @dfee seems to be using an older astroid release.

@dfee Like @PCManticore said, if you're still having issues with an up-to-date pylint/astroid, please open a separate issue, with some more information than "it's not supported" - no issues here with attrs ever since this was closed.

zadamah · 2018-08-01T09:12:08Z

Actually I replied to @dfee here but it is about pylint-dev/astroid#479:

it was merged to astroid master on January
but it was not merged to the release branch 2.0 (last I checked)
so what I am not sure of is what can we do so that this feature is on the next astroid release and then in pylint as well ?

And obviously I completely agree what @PCManticore is saying. pylint is actually one of my favorite Python tools. I just want this feature to be available to everyone.

PCManticore · 2018-08-01T09:23:59Z

@zadamah from what I can see your fix landed in the released version: https://github.com/PyCQA/astroid/blob/master/astroid/brain/brain_attrs.py. if it's in the master branch, then most likely it is released. Are you referring though to the 2.0 branch from astroid? If so, that's somewhat unrelated to the actual 2.0 release, since it is mostly an old refactoring branch that never got merged back.

zadamah · 2018-08-01T09:49:22Z

Yes I was referring to branch "2.0" from astroid, it got me a little confused.
And you are right, I haven't checked for while, but now I can see the changes in brain_attrs.py after upgrading to pylint 2.1.0 (and astroid 2.0.2).
Thank you @The-Compiler & @PCManticore.
And @dfee, I think that your issue could be solved by upgrading to the latest pylint release.

Old one runs into pylint-dev/pylint#1698

The-Compiler added a commit to qutebrowser/qutebrowser that referenced this issue Oct 11, 2017

Fix lint

bdc82bc

See pylint-dev/pylint#1698

PCManticore added Needs astroid Brain 🧠 Needs a brain tip in astroid (then an astroid upgrade) Enhancement ✨ Improvement to a component labels Oct 12, 2017

brycepg mentioned this issue Oct 30, 2017

Add Transform Plugin for attr to fix false positives due to instance attribute rewriting pylint-dev/astroid#462

Merged

PCManticore closed this as completed in pylint-dev/astroid#462 Dec 11, 2017

zadamah mentioned this issue Jan 17, 2018

handle case of "attr" decorators with arguments pylint-dev/astroid#479

Merged

The-Compiler mentioned this issue Apr 10, 2018

Added prototype for the configuration file kitovu-bot/kitovu#6

Merged

mthuurne mentioned this issue Apr 20, 2020

False positive on arguments of constructor created by "attrs" #3492

Open

efiop added a commit to efiop/dvc-data that referenced this issue Aug 11, 2023

tests: bump pylint

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Old one runs into pylint-dev/pylint#1698

efiop added a commit to efiop/dvc-data that referenced this issue Aug 11, 2023

tests: bump pylint

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Old one runs into pylint-dev/pylint#1698

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Old one runs into pylint-dev/pylint#1698

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Support the "attrs" library #1698

Support the "attrs" library #1698

The-Compiler commented Oct 11, 2017

PCManticore commented Oct 12, 2017

tedbrandston commented Jan 2, 2018

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Support the "attrs" library #1698

Support the "attrs" library #1698

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The-Compiler commented Oct 11, 2017

PCManticore commented Oct 12, 2017

tedbrandston commented Jan 2, 2018

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dfee commented Aug 1, 2018

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