***************************
 What's New in Pylint 4.0
***************************

.. toctree::
   :maxdepth: 2

:Release:4.0
:Date: TBA

Summary -- Release highlights
=============================

.. towncrier release notes start

What's new in Pylint 4.0.0?
---------------------------
Release date: TBA


Breaking Changes
----------------

- Commented out code blocks such as ``#    bar() # TODO: remove dead code`` will no longer emit ``fixme``.

  Refs #9255 (`#9255 <https://github.com/pylint-dev/pylint/issues/9255>`_)

- `pyreverse` `Run` was changed to no longer call `sys.exit()` in its `__init__`.
  You should now call `Run(args).run()` which will return the exit code instead.
  Having a class that always raised a `SystemExit` exception was considered a bug.

  Normal usage of pyreverse through the CLI will not be affected by this change.

  Refs #9689 (`#9689 <https://github.com/pylint-dev/pylint/issues/9689>`_)

- The ``async.py`` checker module has been renamed to ``async_checker.py`` since ``async`` is a Python keyword
  and cannot be imported directly. This allows for better testing and extensibility of the async checker functionality.

  Refs #10071 (`#10071 <https://github.com/pylint-dev/pylint/issues/10071>`_)



New Features
------------

- The `fixme` check can now search through docstrings as well as comments, by using
  ``check-fixme-in-docstring = true`` in the ``[tool.pylint.miscellaneous]`` section.

  Closes #9255 (`#9255 <https://github.com/pylint-dev/pylint/issues/9255>`_)



False Positives Fixed
---------------------

- Fix a false positive for `used-before-assignment` when a variable defined under
  an `if` and via a named expression (walrus operator) is used later when guarded
  under the same `if` test.

  Closes #10061 (`#10061 <https://github.com/pylint-dev/pylint/issues/10061>`_)

- Fix a false positive for `use-implicit-booleaness-not-len`. No lint should be emitted for
  generators (`len` is not defined for generators).

  Refs #10100 (`#10100 <https://github.com/pylint-dev/pylint/issues/10100>`_)



False Negatives Fixed
---------------------

- Fix false negative for `used-before-assignment` when a `TYPE_CHECKING` import is used as a type annotation prior to erroneous usage.

  Refs #8893 (`#8893 <https://github.com/pylint-dev/pylint/issues/8893>`_)

- Fix false negative for `used-before-assignment` when a function is defined inside a `TYPE_CHECKING` guard block and used later.

  Closes #10028 (`#10028 <https://github.com/pylint-dev/pylint/issues/10028>`_)