pytest-flake8-path 1.7.0
A pytest fixture for testing flake8 plugins.
Requires Python: >=3.9
Keywords: flake8, pytest

==================
pytest-flake8-path
==================

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A pytest fixture for testing flake8 plugins.

A quick example:

.. code-block:: python

    def test_simple_run(flake8_path):
        (flake8_path / "example.py").write_text("x  = 1\n")

        result = flake8_path.run_flake8()

        assert result.out_lines == [
            "./example.py:1:2: E221 multiple spaces before operator"
        ]

----

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----

Installation
============

Use **pip**:

.. code-block:: sh

    python -m pip install pytest-flake8-path

Python 3.9 to 3.14 supported.

API
===

``flake8_path`` fixture
-----------------------

A pytest fixture that wraps Pytest's built-in ``tmp_path`` fixture
(`docs <https://docs.pytest.org/en/latest/how-to/tmp_path.html>`__), to create
a temporary directory, allow adding files, and running flake8. It acts like a
`pathlib.Path <https://docs.python.org/3/library/pathlib.html#pathlib.Path>`__
object, with one extra method.

If you're using this to test a flake8 plugin, make sure flake8 is picking up
your plugin during tests. Normally this is done with a ``setup.cfg``
entrypoint, which makes ``tox`` the easiest way to guarantee this is ready as
it will install your project before running tests.

``flake8dir.run_flake8(extra_args: list[str] | None = None) -> Flake8Result``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Runs flake8 and returns a ``Flake8Result`` representing the results.

``extra_args`` may be a list of extra flags to pass to flake8, for example
passing ``["--ignore", "E101"]``. Note some arguments are already passed to
ensure Flake8 runs in an isolated manner - see source.

``Flake8Result``
----------------

Represents the parsed output of a flake8 run.

``Flake8Result.out: str``
~~~~~~~~~~~~~~~~~~~~~~~~~

The full string of output (stdout) generated by flake8.

``Flake8Result.err: str``
~~~~~~~~~~~~~~~~~~~~~~~~~

The full string of error output (stderr) generated by flake8.

``Flake8Result.exit_code: int``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The exit code that the flake8 run exited with.

``Flake8Result.out_lines: list[str]``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

A list of individual lines of output, without trailing newlines.
This is the most useful tool for making assertions against.

On Windows, file paths are normalized into the Unix format (``\`` is replaced
with ``/``). This allows test suites to run the same on all operating systems.

For example, given a result you can check for a particular line being output:

.. code-block:: python

    result = flake8_path.run_flake8()
    expected = "./example.py:1:2: E221 multiple spaces before operator"
    assert expected in result.out_lines

``Flake8Result.err_lines: list[str]``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Like ``out_lines``, but for error output.

Examples
========

Basic
-----

Using ``Path.write_text()`` (`docs <https://docs.python.org/3/library/pathlib.html#pathlib.Path.write_text>`__) we can create an ``example.py`` file with code.
Then with ``flake8_path.run_flake8()`` we can run flake8 and check for an expected error:

.. code-block:: python

    def test_simple(flake8_path):
        (flake8_path / "example.py").write_text("x  = 1\n")

        result = flake8_path.run_flake8()

        assert result.out_lines == [
            "./example.py:1:2: E221 multiple spaces before operator"
        ]
        assert result.err_lines == []
        assert result.exit_code == 1

With dedent
-----------

The standard library’s ``textwrap.dedent()`` (`docs <https://docs.python.org/3/library/textwrap.html#textwrap.dedent>`__) is useful for including multi-line files.
Use a triple quoted multi-line string, with an initial backslash to prevent a blank first line:

.. code-block:: python

    def test_multi_line(flake8_path):
        (flake8_path / "example.py").write_text(
            dedent(
                """\
                x  = 1
                y  = 2
                """
            )
        )

        result = flake8_path.run_flake8()

        assert result.out_lines == [
            "./example.py:1:2: E221 multiple spaces before operator",
            "./example.py:2:2: E221 multiple spaces before operator",
        ]
        assert result.err_lines == []
        assert result.exit_code == 1

Configuring flake8
------------------

Write a ``setup.cfg`` file to configure flake8 before running it:

.. code-block:: python

    def test_with_setup_cfg(flake8_path):
        (flake8_path / "setup.cfg").write_text(
            dedent(
                """\
                [flake8]
                ignore = E221
                """
            )
        )
        (flake8_path / "example.py").write_text("x  = 1\n")

        result = flake8_path.run_flake8()

        assert result.out_lines == []
        assert result.err_lines == []
        assert result.exit_code == 0

History
=======

pytest-flake8-path is the successor to `pytest-flake8dir <https://pypi.org/project/pytest-flake8dir/>`__.
pytest-flake8dir was based upon pytest’s ``tmpdir`` fixture, which returned a legacy ``py.path.local`` object.
Since version 3.9.0, pytest has provided the ``tmp_path`` fixture, which returns a standard library ``pathlib.Path`` object.
pytest-flake8-path is a rewrite of pytest-flake8dir to use ``tmp_path`` instead of ``tmpdir``.