len-as-condition: fix false positives when len() wasn't used in logic…

…al test (#1332) Closes #1325 and #1331
pylint-dev · Feb 21, 2017 · ea964a0 · ea964a0
1 parent d274655
commit ea964a0
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Showing 3 changed files with 25 additions and 3 deletions.
diff --git a/pylint/checkers/refactoring.py b/pylint/checkers/refactoring.py
@@ -653,9 653,11 @@ def visit_call(self, node):
 
  # we're finally out of any nested boolean operations so check if
  # this len() call is part of a test condition
- if _node_is_test_condition(parent):
- self.add_message('len-as-condition', node=node)
-
  if not _node_is_test_condition(parent):
  return
  if not (node is parent.test or parent.test.parent_of(node)):
  return
  self.add_message('len-as-condition', node=node)
 
  @utils.check_messages('len-as-condition')
  def visit_unaryop(self, node):

diff --git a/pylint/test/functional/len_checks.py b/pylint/test/functional/len_checks.py
@@ -45,3 45,21 @@
 
 def some_func():
  return len('TEST') > 0 # Should be fine
 
 
 def github_issue_1325():
  l = [1, 2, 3]
  length = len(l) if l else 0
  return length
 
 
 def github_issue_1331(*args):
  assert False, len(args)
 
 
 def github_issue_1331_v2(*args):
  assert len(args), args # [len-as-condition]
 
 
 def github_issue_1331_v3(*args):
  assert len(args) or z, args # [len-as-condition]
diff --git a/pylint/test/functional/len_checks.txt b/pylint/test/functional/len_checks.txt
@@ -8,3 8,5 @@ len-as-condition:20::Do not use `len(SEQUENCE)` as condition value
 len-as-condition:26::Do not use `len(SEQUENCE)` as condition value
 len-as-condition:30::Do not use `len(SEQUENCE)` as condition value
 len-as-condition:43::Do not use `len(SEQUENCE)` as condition value
 len-as-condition:61:github_issue_1331_v2:Do not use `len(SEQUENCE)` as condition value
 len-as-condition:65:github_issue_1331_v3:Do not use `len(SEQUENCE)` as condition value