Summary -- Release highlights

With 2.14 pylint only supports Python version 3.7.2 and above.

We introduced several new checks among which duplicate-value for sets,
comparison-of-constants, and checks related to lambdas. We removed no-init and
made no-self-use optional as they were too opinionated. We also added an option
to generate a toml configuration: --generate-toml-config.

We migrated to argparse from optparse and refactored the configuration handling
thanks to Daniël van Noord. On the user side it should change the output of the
--help command, and some inconsistencies and bugs should disappear. The behavior
between options set in a config file versus on the command line will be more consistent. For us,
it will permit to maintain this part of the code easily in the future and anticipate
optparse's removal in Python 3.12.

As a result of the refactor there are a lot of internal deprecations. If you're a library
maintainer that depends on pylint, please verify that you're ready for pylint 3.0
by activating deprecation warnings.

We continued the integration of pylint-error and are now at 33%!. We still welcome
any community effort to help review, integrate, and add good/bad examples in #5953.
This should be doable without any pylint or astroid knowledge, so this is the perfect
entrypoint if you want to contribute to pylint or open source without any experience
with our code!

New checkers

Added new checker comparison-of-constants.
Closes #6076
Added new checker typevar-name-mismatch: TypeVar must be assigned to a variable with the same name as its name argument.
Closes #5224
invalid-enum-extension: Used when a class tries to extend an inherited Enum class.
Closes #5501
Added new checker typevar-double-variance: The "covariant" and "contravariant" keyword arguments
cannot both be set to "True" in a TypeVar.
Closes #5895
Add new check unnecessary-dunder-call for unnecessary dunder method calls.
Closes #5936
unnecessary-lambda-assignment: Lambda expression assigned to a variable.
Define a function using the "def" keyword instead.
unnecessary-direct-lambda-call: Lambda expression called directly.
Execute the expression inline instead.
Closes #5976
potential-index-error: Emitted when the index of a list or tuple exceeds its length.
This checker is currently quite conservative to avoid false positives. We welcome
suggestions for improvements.
Closes #578
Added new checker unnecessary-list-index-lookup for indexing into a list while
iterating over enumerate().
Closes #4525
Added new message called duplicate-value which identifies duplicate values inside sets.
Closes #5880
Added the super-without-brackets checker, raised when a super call is missing its brackets.
Closes #4008

Removed checkers

The no-init (W0232) warning has been removed. It's ok to not have an __init__ in a class.
Closes #2409
Removed the assign-to-new-keyword message as there are no new keywords in the supported Python
versions any longer.
Closes #4683
Moved no-self-use check to optional extension.
You now need to explicitly enable this check using
load-plugins=pylint.extensions.no_self_use.
Closes #5502

Extensions

RedefinedLoopNameChecker
- Added optional extension redefined-loop-name to emit messages when a loop variable
  is redefined in the loop body.
Closes #5072
DocStringStyleChecker
- Re-enable checker bad-docstring-quotes for Python <= 3.7.
Closes #6087
NoSelfUseChecker
- Added no-self-use check, previously enabled by default.
Closes #5502

Other Changes

Started ignoring underscore as a local variable for too-many-locals.
Closes #6488
Pylint can now be installed with an extra-require called spelling (pip install pylint[spelling]).
This will add pyenchant to pylint's dependencies. You will still need to install the
requirements for pyenchant (the enchant library and any dictionaries) yourself. You will also
need to set the spelling-dict option.
Refs #6462
Improved wording of the message of deprecated-module
Closes #6169
Pylint now requires Python 3.7.2 or newer to run.
Closes #4301
We made a greater effort to reraise failures stemming from the astroid
library as AstroidError, with the effect that pylint emits astroid-error
rather than merely fatal. Regardless, please report any such issues you encounter!
We have improved our recognition of inline disable and enable comments. It is
now possible to disable bad-option-value inline (as long as you disable it before
the bad option value is raised, i.e. disable=bad-option-value,bad-message not disable=bad-message,bad-option-value ) as well as certain other
previously unsupported messages.
Closes #3312
The main checker name is now main instead of master. The configuration does not need to be updated as sections' name are optional.
Closes #5467
Update invalid-slots-object message to show bad object rather than its inferred value.
Closes #6101
Fixed a crash in the not-an-iterable checker involving multiple starred expressions
inside a call.
Closes #6372
Fixed a crash in the unused-private-member checker involving chained private attributes.
Closes #6709
Disable spellchecking of mypy rule names in ignore directives.
Closes #5929
implicit-str-concat will now be raised on calls like open("myfile.txt" "a+b") too.
Closes #6441
Fix a failure to respect inline disables for fixme occurring on the last line
of a module when pylint is launched with --enable=fixme.
Removed the broken generate-man option.
Closes #5283
Closes #1887
Fixed failure to enable deprecated-module after a disable=all
by making ImportsChecker solely responsible for emitting deprecated-module instead
of sharing responsibility with StdlibChecker. (This could have led to double messages.)
Added the generate-toml-config option.
Refs #5462
bad-option-value will be emitted whenever a configuration value or command line invocation
includes an unknown message.
Closes #4324
Added the unrecognized-option message. Raised if we encounter any unrecognized options.
Closes #5259
Fix false negative for bad-string-format-type if the value to be formatted is passed in
as a variable holding a constant.
The concept of checker priority has been removed.
The cache-max-size-none checker has been renamed to method-cache-max-size-none.
Closes #5670
The method-cache-max-size-none checker will now also check functools.cache.
Closes #5670
BaseChecker classes now require the linter argument to be passed.
The set_config_directly decorator has been removed.
Don't report useless-super-delegation for the __hash__ method in classes that also override the __eq__ method.
Closes #3934
Fix falsely issuing useless-suppression on the wrong-import-position checker.
Closes #5219
Fixed false positive no-member for Enums with self-defined members.
Closes #5138
Fix false negative for no-member when attempting to assign an instance
attribute to itself without any prior assignment.
Closes #1555
Changed message type from redefined-outer-name to redefined-loop-name
(optional extension) for redefinitions of outer loop variables by inner loops.
Closes #5608
By default the similarity checker will now ignore imports and ignore function signatures when computing
duplication. If you want to keep the previous behaviour set ignore-imports and ignore-signatures to False.
Pylint now expands the user path (i.e. ~ to home/yusef/) and expands environment variables (i.e. home/$USER/$project
to home/yusef/pylint for USER=yusef and project=pylint) for pyreverse's output-directory,
import-graph, ext-import-graph, int-import-graph options, and the spell checker's spelling-private-dict-file
option.
Refs #6493
Don't emit unsubscriptable-object for string annotations.
Pylint doesn't check if class is only generic in type stubs only.
Closes #4369 and #6523
Fix pyreverse crash RuntimeError: dictionary changed size during iteration
Refs #6612
Fix syntax for return type annotations in MermaidJS diagrams produced with pyreverse.
Closes #6467
Fix type annotations of class and instance attributes using the alternative union syntax in pyreverse diagrams.
Fix bug where it writes a plain text error message to stdout, invalidating output formats.
Closes #6597
The refactoring checker now also raises 'consider-using-a-generator' messages for
max(), min() and sum().
Refs #6595
Update ranges for using-constant-test and missing-parentheses-for-call-in-test
error messages.
Don't emit no-member inside type annotations with
from __future__ import annotations.
Closes #6594
Fix unexpected-special-method-signature false positive for __init_subclass__ methods with one or more arguments.
Closes #6644

Deprecations

The ignore-mixin-members option has been deprecated. You should now use the new
ignored-checks-for-mixins option.
Closes #5205
interfaces.implements has been deprecated and will be removed in 3.0. Please use standard inheritance
patterns instead of __implements__.
Refs #2287
All Interface classes in pylint.interfaces have been deprecated. You can subclass
the respective normal classes to get the same behaviour. The __implements__ functionality
was based on a rejected PEP from 2001:
https://peps.python.org/pep-0245/
Closes #2287
MapReduceMixin has been deprecated. BaseChecker now implements get_map_data and
reduce_map_data. If a checker actually needs to reduce data it should define get_map_data
as returning something different than None and let its reduce_map_data handle a list
of the types returned by get_map_data.
An example can be seen by looking at pylint/checkers/similar.py.
The config attribute of BaseChecker has been deprecated. You can use checker.linter.config
to access the global configuration object instead of a checker-specific object.
Refs #5392
The level attribute of BaseChecker has been deprecated: everything is now
displayed in --help, all the time.
Refs #5392
The set_option method of BaseChecker has been deprecated. You can use checker.linter.set_option
to set an option on the global configuration object instead of a checker-specific object.
Refs #5392
The options_providers attribute of ArgumentsManager has been deprecated.
Refs #5392
Fix saving of persistent data files in environments where the user's cache
directory and the linted file are on a different drive.
Closes #6394
The method-cache-max-size-none checker will now also check functools.cache.
The config attribute of PyLinter is now of the argparse.Namespace type instead of
optparse.Values.
Refs #5392
UnsupportedAction has been deprecated.
Refs #5392
OptionsManagerMixIn has been deprecated.
Refs #5392
OptionParser has been deprecated.
Refs #5392
Option has been deprecated.
Refs #5392
OptionsProviderMixIn has been deprecated.
Refs #5392
ConfigurationMixIn has been deprecated.
The option_groups attribute of PyLinter has been deprecated.
Refs #5392
get_global_config has been deprecated. You can now access all global options from
checker.linter.config.
Refs #5392
OptionsManagerMixIn has been replaced with ArgumentsManager. ArgumentsManager is considered
private API and most methods that were public on OptionsManagerMixIn have now been deprecated and will
be removed in a future release.
Refs #5392
OptionsProviderMixIn has been replaced with ArgumentsProvider. ArgumentsProvider is considered
private API and most methods that were public on OptionsProviderMixIn have now been deprecated and will
be removed in a future release.
Refs #5392
pylint.pyreverse.ASTWalker has been removed, as it was only used internally by a single child class.
Refs #6712
pyreverse: Resolving and displaying implemented interfaces that are defined by the __implements__
attribute has been deprecated and will be removed in 3.0.
Refs #6713
is_class_subscriptable_pep585_with_postponed_evaluation_enabled has been deprecated.
Use is_postponed_evaluation_enabled(node) and is_node_in_type_annotation_context(node)
instead.
Refs #6536

pylint-dev/pylint v2.14.0 on GitHub