1===================
2Python Coding style
3===================
4
5Coding style
6~~~~~~~~~~~~
7
8 :ref:`black` is the tool used to reformat the Python code.
9
10Linting
11~~~~~~~
12
13The Python linting is done by :ref:`Flake8` and :ref:`pylint`
14They are executed by mozlint both at review phase and in the CI.
15
16Indentation
17~~~~~~~~~~~
18
19Four spaces in Python code.
20
21
22Makefile/moz.build practices
23----------------------------
24
25-  Changes to makefile and moz.build variables do not require
26   build-config peer review. Any other build system changes, such as
27   adding new scripts or rules, require review from the build-config
28   team.
29-  Suffix long ``if``/``endif`` conditionals with #{ & #}, so editors
30   can display matched tokens enclosing a block of statements.
31
32   ::
33
34      ifdef CHECK_TYPE #{
35        ifneq ($(flavor var_type),recursive) #{
36          $(warning var should be expandable but detected var_type=$(flavor var_type))
37        endif #}
38      endif #}
39
40-  moz.build are python and follow normal Python style.
41-  List assignments should be written with one element per line. Align
42   closing square brace with start of variable assignment. If ordering
43   is not important, variables should be in alphabetical order.
44
45   .. code-block:: python
46
47      var += [
48          'foo',
49          'bar'
50      ]
51
52-  Use ``CONFIG['CPU_ARCH'] {=arm}`` to test for generic classes of
53   architecture rather than ``CONFIG['OS_TEST'] {=armv7}`` (re: bug 886689).
54
55
56Other advices
57~~~~~~~~~~~~~
58
59-  Install the
60   `mozext <https://hg.mozilla.org/hgcustom/version-control-tools/file/default/hgext/mozext>`__
61   Mercurial extension, and address every issue reported on commit
62   or the output of ``hg critic``.
63-  Follow `PEP 8 <https://www.python.org/dev/peps/pep-0008/>`__. Please run :ref:`black` for this.
64-  Do not place statements on the same line as ``if/elif/else``
65   conditionals to form a one-liner.
66-  Global vars, please avoid them at all cost.
67-  Exclude outer parenthesis from conditionals.Use
68   ``if x > 5:,``\ rather than ``if (x > 5):``
69-  Use string formatters, rather than var + str(val).
70   ``var = 'Type %s value is %d'% ('int', 5).``
71-  Testing/Unit tests, please write them and make sure that they are executed in the CI.
72