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50 lines
1.7 KiB
ReStructuredText
50 lines
1.7 KiB
ReStructuredText
===========================================
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Developing a Formatting Plugin for Flake8
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===========================================
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Flake8 added the ability to develop custom formatting plugins in version
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3.0.0. Let's write a plugin together:
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.. code-block:: python
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from flake8.formatting import base
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class Example(base.BaseFormatter):
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"""Flake8's example formatter."""
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pass
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We notice, as soon as we start, that we inherit from Flake8's
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:class:`~flake8.formatting.base.BaseFormatter` class. If we follow the
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:ref:`instructions to register a plugin <register-a-plugin>` and try to use
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our example formatter, e.g., ``flake8 --format=example`` then Flake8 will fail
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because we did not implement the ``format`` method. Let's do that next.
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.. code-block:: python
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class Example(base.BaseFormatter):
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"""Flake8's example formatter."""
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def format(self, error):
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return 'Example formatter: {0!r}'.format(error)
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With that we're done. Obviously this isn't a very useful formatter, but it
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should highlight the simplicitly of creating a formatter with Flake8. If we
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wanted to instead create a formatter that aggregated the results and returned
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XML, JSON, or subunit we could also do that. Flake8 interacts with the
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formatter in two ways:
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#. It creates the formatter and provides it the options parsed from the
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configuration files and command-line
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#. It uses the instance of the formatter and calls ``handle`` with the error.
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By default :meth:`flake8.formatting.base.BaseFormatter.handle` simply calls
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the ``format`` method and then ``write``. Any extra handling you wish to do
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for formatting purposes should override the ``handle`` method.
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API Documentation
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=================
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.. autoclass:: flake8.formatting.base.BaseFormatter
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