mirror of
https://github.com/PyCQA/flake8.git
synced 2026-04-06 13:06:53 +00:00
106 lines
3.4 KiB
ReStructuredText
106 lines
3.4 KiB
ReStructuredText
.. _checker-plugins:
|
|
|
|
===============
|
|
Checker Plugins
|
|
===============
|
|
|
|
A |Flake8| checker plugin needs to have a registered entry point. This entry
|
|
point must reference a callable object.
|
|
|
|
|
|
Declaring the type of plugin
|
|
============================
|
|
|
|
Flake8 uses certain key parameters to determine the kind of plugin this is and
|
|
how it needs to call it:
|
|
|
|
* If it has a parameter called ``tree`` then this plugin is considered to be an
|
|
AST checker plugin. It will be called once per file and it will receive the
|
|
parsed AST of the file as the ``tree`` parameter. If this entry point
|
|
references a class, then the call will construct an instance of such class,
|
|
and Flake8 will then call the ``run()`` method on the created object to get
|
|
results.
|
|
* If the callable has a parameter called ``physical_line`` then whatever the
|
|
entry point references is called for each physical line and the call is
|
|
expected to yield results directly.
|
|
* If the callable has a parameter called ``logical_line`` then the callable
|
|
referred to by the entry point will be called from |Flake8| with each logical
|
|
line and is expected to yield results.
|
|
|
|
|
|
.. note::
|
|
|
|
Class-style plugins are only supported for AST checker (*tree*) plugins.
|
|
|
|
|
|
The Results
|
|
===========
|
|
|
|
Tree plugins
|
|
------------
|
|
|
|
A tree plugin can be a function or a class. If it is a function, it must take
|
|
a parameter called ``tree``. If it is a class, then the ``__init__`` method
|
|
must take this parameter.
|
|
|
|
For a class-based plugin, the ``run`` method is in charge of yielding results.
|
|
For functions, they must deliver results directly.
|
|
|
|
|Flake8| expects the result of running these plugins to be an iterable of
|
|
tuples, each of which contain the following:
|
|
|
|
* An ``int`` with the line number where the issue appears
|
|
|
|
* An ``int`` with the offset within the line where the issue appears (column)
|
|
|
|
* A ``str`` with the error message
|
|
|
|
* The source of the error (typically the name of the plugin). Although this
|
|
field is not used by |Flake8|, it must be present in each tuple
|
|
|
|
|
|
Physical Line plugins
|
|
---------------------
|
|
|
|
A Physical Line plugin must be callable, it must take a parameter called
|
|
``physical_line`` and it must return the result of checking the passed physical
|
|
line.
|
|
|
|
|Flake8| expects the result of this call to be an iterable of tuples, each
|
|
containing the following:
|
|
|
|
* An ``int`` with the offset within the line where the reported issue appears
|
|
|
|
* A ``str`` with the error message
|
|
|
|
|
|
Logical Line Plugins
|
|
--------------------
|
|
|
|
A Logical Line plugin must be callable, it must take a parameter called
|
|
``logical_line`` and it must return the result of checking the passed logical
|
|
line.
|
|
|
|
|Flake8| expects the result of this call to be an iterable of tuples, each
|
|
containing the following:
|
|
|
|
* An ``int`` with the offset within the logical line where the reported issue
|
|
appears
|
|
|
|
* A ``str`` with the error message
|
|
|
|
|Flake8| will take care of the conversion from the reported offset on the
|
|
logical line to a physical line and physical column pair before it outputs
|
|
errors to the user.
|
|
|
|
|
|
Video Tutorial
|
|
==============
|
|
|
|
Here's a tutorial which goes over building an AST checking plugin from scratch:
|
|
|
|
.. raw:: html
|
|
|
|
<div style="position: relative; padding-bottom: 56.25%; height: 0; overflow: hidden; max-width: 100%; height: auto; margin-bottom: 1em;">
|
|
<iframe src="https://www.youtube.com/embed/ot5Z4KQPBL8" frameborder="0" allowfullscreen style="position: absolute; top: 0; left: 0; width: 100%; height: 100%;"></iframe>
|
|
</div>
|