Python Coding style — Firefox Source Docs documentation (original) (raw)

Firefox Source Docs

Coding style

Black is the tool used to reformat the Python code.

Linting

The Python linting is done by Flake8 and pylintThey are executed by mozlint both at review phase and in the CI.

Indentation

Four spaces in Python code.

Makefile/moz.build practices

• Changes to makefile and moz.build variables do not require build-config peer review. Any other build system changes, such as adding new scripts or rules, require review from the build-config team.
• Suffix long if/endif conditionals with #{ & #}, so editors can display matched tokens enclosing a block of statements.
  ifdef CHECK_TYPE #{
  ifneq ($(flavor var_type),recursive) #{
  (warningvarshouldbeexpandablebutdetectedvartype=(warning var should be expandable but detected var_type=(warningvarshouldbeexpandablebutdetectedvart​ype=(flavor var_type))
  endif #}
  endif #}
• moz.build are python and follow normal Python style.
• List assignments should be written with one element per line. Align closing square brace with start of variable assignment. If ordering is not important, variables should be in alphabetical order.
• Use CONFIG['TARGET_CPU'] {=arm} to test for generic classes of architecture rather than CONFIG['OS_TEST'] {=armv7} (re: bug 886689).

Other advice

• Install themozextMercurial extension, and address every issue reported on commit or the output of hg critic.
• Follow PEP 8. Please run Black for this.
• Do not place statements on the same line as if/elif/elseconditionals to form a one-liner.
• Global vars, please avoid them at all cost.
• Exclude outer parenthesis from conditionals.Useif x > 5:,rather than if (x > 5):
• Use string formatters, rather than var + str(val).var = 'Type %s value is %d'% ('int', 5).
• Testing/Unit tests, please write them and make sure that they are executed in the CI.