Added D404: First word of a docstring should not be This

Author: Nurdok

src/pydocstyle.py

@@ -703,6 +703,8 @@ def to_rst(cls):
                                  '"signature"')
 D403 = D4xx.create_error('D403', 'First word of the first line should be '
                                  'properly capitalized', '%r, not %r')
+D404 = D4xx.create_error('D404', 'First word of the docstring should not '
+                                 'be `This`')
 
 
 class AttrDict(dict):
@@ -711,8 +713,10 @@ def __getattr__(self, item):
 
 
 conventions = AttrDict({
-    'pep257': set(ErrorRegistry.get_error_codes()) - set(['D203', 'D212',
-                                                          'D213'])
+    'pep257': set(ErrorRegistry.get_error_codes()) - set(['D203',
+                                                          'D212',
+                                                          'D213',
+                                                          'D404'])
 })
 
 
@@ -1435,7 +1439,6 @@ def check_no_blank_before(self, function, docstring):  # def
         There's no blank line either before or after the docstring.
 
         """
-        # NOTE: This does not take into account functions with groups of code.
         if docstring:
             before, _, after = function.source.partition(docstring)
             blanks_before = list(map(is_blank, before.split('\n')[:-1]))
@@ -1684,6 +1687,19 @@ def check_capitalized(self, function, docstring):
             if first_word != first_word.capitalize():
                 return D403(first_word.capitalize(), first_word)
 
+    @check_for(Definition)
+    def check_starts_with_this(self, function, docstring):
+        """D404: First word of the docstring should not be `This`.
+
+        Docstrings should use short, simple language. They should not begin
+        with "This class is [..]" or "This module contains [..]".
+
+        """
+        if docstring:
+            first_word = ast.literal_eval(docstring).split()[0]
+            if first_word.lower() == 'this':
+                return D404()
+
     # Somewhat hard to determine if return value is mentioned.
     # @check(Function)
     def SKIP_check_return_type(self, function, docstring):

src/tests/test_cases/unicode_literals.py

@@ -1,5 +1,5 @@
 # -*- coding: utf-8 -*-
-"""This is a module."""
+"""A module."""
 
 from __future__ import unicode_literals
 from .expected import Expectation

src/tests/test_decorators.py

@@ -13,7 +13,7 @@
 from .. import pydocstyle
 
 
-class TestParser:
+class TestParser(object):
     """Check parsing of Python source code."""
 
     def test_parse_class_single_decorator(self):

src/tests/test_definitions.py

@@ -253,8 +253,8 @@ def test_token_stream():
     assert stream.line == 1
 
 
-def test_pep257():
-    """Run domain-specific tests from test.py file."""
+def test_example_files():
+    """Run domain-specific tests from test case files."""
     test_cases = (
         'test',
         'unicode_literals',
@@ -275,4 +275,4 @@ def test_pep257():
         for error in results:
             assert isinstance(error, Error)
         results = set([(e.definition.name, e.message) for e in results])
-        assert case_module.expectation.expected == results
+        assert case_module.expectation.expected == results, test_case