# HG changeset patch
# User Pierre-Yves David <pierre-yves.david@fb.com>
# Date 2015-09-24 07:34:15
# Node ID b80b2ee71a08d00ec4008f3131bdf3c72e4ec2ba
# Parent  e9a35411bbbcf7c09ab002fca424ce982d8b3dc5

check-code: forbid mutable value for default argument

default value are common to all call. Using mutable value is a classical source
of bug in Python. We forbid it.

The regexp (Courtesy of Matt Mackall) is only catching such value on the first
line of a definition, but that will be good enough for now.

diff --git a/contrib/check-code.py b/contrib/check-code.py
--- a/contrib/check-code.py
+++ b/contrib/check-code.py
@@ -291,6 +291,8 @@ pypats = [
     (r'os\.path\.join\(.*, *(""|\'\')\)',
      "use pathutil.normasprefix(path) instead of os.path.join(path, '')"),
     (r'\s0[0-7]+\b', 'legacy octal syntax; use "0o" prefix instead of "0"'),
+    # XXX only catch mutable arguments on the first line of the definition
+    (r'def.*[( ]\w+=\{\}', "don't use mutable default arguments"),
   ],
   # warnings
   [