1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
|
Writing an Extension for Flake8
===============================
Since Flake8 is now adding support for extensions, we require ``setuptools``
so we can manage extensions through entry points. If you are making an
existing tool compatible with Flake8 but do not already require
``setuptools``, you should probably add it to your list of requirements. Next,
you'll need to edit your ``setup.py`` file so that upon installation, your
extension is registered. If you define a class called ``PackageEntryClass``
then this would look something like the following::
setup(
# ...
entry_points={
'flake8.extension': ['P10 = package.PackageEntryClass'],
}
# ...
)
If you intend to publish your extension, choose a unique code prefix
following the convention for :ref:`error codes <error-codes>`.
In addition, you can open a request in the `issue tracker
<https://bitbucket.org/tarek/flake8/issues>`_ to register the prefix in the
documentation.
.. TODO: describe the API required for the 3 kind of extensions:
* physical line checkers
* logical line checkers
* AST checkers
A real example: McCabe
----------------------
Below is an example from mccabe_ for how to write your ``setup.py`` file for
your Flake8 extension.
.. code-block:: python
# https://github.com/flintwork/mccabe/blob/0.2/setup.py#L38:L42
# -*- coding: utf-8 -*-
from setuptools import setup
# ...
setup(
name='mccabe',
# ...
install_requires=[
'setuptools',
],
entry_points={
'flake8.extension': [
'C90 = mccabe:McCabeChecker',
],
},
# ...
)
In ``mccabe.py`` you can see that extra options are added to the parser when
flake8 registers the extension:
.. code-block:: python
# https://github.com/flintwork/mccabe/blob/0.2/mccabe.py#L225:L254
class McCabeChecker(object):
"""McCabe cyclomatic complexity checker."""
name = 'mccabe'
version = __version__
_code = 'C901'
_error_tmpl = "C901 %r is too complex (%d)"
max_complexity = 0
def __init__(self, tree, filename):
self.tree = tree
@classmethod
def add_options(cls, parser):
parser.add_option('--max-complexity', default=-1, action='store',
type='int', help="McCabe complexity threshold")
parser.config_options.append('max-complexity')
@classmethod
def parse_options(cls, options):
cls.max_complexity = options.max_complexity
def run(self):
if self.max_complexity < 0:
return
visitor = PathGraphingAstVisitor()
visitor.preorder(self.tree, visitor)
for graph in visitor.graphs.values():
if graph.complexity() >= self.max_complexity:
text = self._error_tmpl % (graph.entity, graph.complexity())
yield graph.lineno, 0, text, type(self)
Since that is the defined entry point in the above ``setup.py``, flake8 finds
it and uses it to register the extension.
Existing Extensions
===================
This is not at all a comprehensive listing of existing extensions but simply a
listing of the ones we are aware of:
* `flake8-debugger <https://github.com/JBKahn/flake8-debugger>`_
* `flake8-immediate <https://github.com/schlamar/flake8-immediate>`_
* `flake8-print <https://github.com/JBKahn/flake8-print>`_
* `flake8-todo <https://github.com/schlamar/flake8-todo>`_
* `pep8-naming <https://github.com/flintwork/pep8-naming>`_
* `radon <https://github.com/rubik/radon>`_
* `flake8-import-order <https://github.com/public/flake8-import-order>`_
.. links
.. _mccabe: https://github.com/flintwork/mccabe
.. _PyPI: https://pypi.python.org/pypi/
|
