missing_else.py

   1 from logilab import astng
   2
   3 from pylint.interfaces import IASTNGChecker
   4 from pylint.checkers import BaseChecker
   5
   6 class MissingElseChecker(BaseChecker):
   7     """
   8     Checks for if blocks that don't have an else clause
   9     """
  10
  11     __implements__ = IASTNGChecker
  12
  13     name = 'missing_else'
  14     msgs = {
  15         'W9901': ('if with no else clause',
  16                   "There's an if block (with no elif) with no else clause"),
  17         'W9902': ('if/elif with no else clause',
  18                   "There's an if/elif set of blocks with no corresponding else clause"),
  19         }
  20     options = (
  21                ('warn_if_no_else',
  22                    {'default': False, 'type': 'yn', 'metavar': '<y_or_n>',
  23                     'help': 'Warn about missing else clause when there is an if (but no elif)'}
  24                    ),
  25                ('warn_if_elif_no_else',
  26                    {'default': True, 'type': 'yn', 'metavar': '<y_or_n>',
  27                     'help': 'Warn about if/elif blocks that have no corresponding else clause'}
  28                    )
  29                )
  30
  31     # this is important so that your checker is executed before others
  32     priority = -1
  33
  34     def visit_if(self, node):
  35         assert len(node.getChildren()) % 2 == 1, "There are an even amount of nodes for "+repr(node)
  36
  37        # True if there is an else clause on this if block
  38         has_else = node.getChildren()[-1] is not None
  39
  40         # True if there are elif methods
  41         has_elifs = len(node.getChildren()) > 3
  42
  43         if self.config.warn_if_no_else and not has_else:
  44             self.add_message('W9901', line=node.lineno)
  45
  46         if self.config.warn_if_elif_no_else and has_elifs and not has_else:
  47             self.add_message('W9902', line=node.lineno)
  48
  49
  50
  51 def register(linter):
  52     """required method to auto register this checker"""
  53     linter.register_checker(MissingElseChecker(linter))
  54