Move TypeVar checks to their our class (#239)

Author: jparise

README.rst

@@ -55,7 +55,7 @@ These error codes are emitted:
 | _`N807` | function name should not start and end with '__'                |
 +---------+-----------------------------------------------------------------+
 | _`N808` | type variable names should use CapWords convention and an       |
-|         | optional suffix '_co' or '_contra' (`type variable names`_)     |
+|         | optional '_co' or '_contra' suffix (`type variable names`_)     |
 +---------+-----------------------------------------------------------------+
 | _`N811` | constant imported as non constant (`constants`_)                |
 +---------+-----------------------------------------------------------------+

src/pep8ext_naming.py

@@ -254,7 +254,6 @@ class ClassNameCheck(BaseASTCheck):
     Classes for internal use have a leading underscore in addition.
     """
     N801 = "class name '{name}' should use CapWords convention"
-    N808 = "type variable name '{name}' should use CapWords convention and an optional suffix '_co' or '_contra'"
     N818 = "exception name '{name}' should be named with an Error suffix"
 
     @classmethod
@@ -276,40 +275,6 @@ def superclass_names(cls, name, parents: Iterable, _names=None):
                 names.update(cls.superclass_names(base.id, parents, names))
         return names
 
-    def visit_module(self, node, parents: Iterable, ignore=None):
-        for body in node.body:
-            try:
-                if len(body.targets) != 1:
-                    continue
-                name = body.targets[0].id
-                func_name = body.value.func.id
-                args = [a.value for a in body.value.args]
-                keywords = {kw.arg: kw.value.value for kw in body.value.keywords}
-            except AttributeError:
-                continue
-
-            if func_name != "TypeVar" or _ignored(name, ignore):
-                continue
-
-            if len(args) == 0 or args[0] != name:
-                yield self.err(body, 'N808', name=name)
-
-            if not name[:1].isupper():
-                yield self.err(body, 'N808', name=name)
-
-            parts = name.split('_')
-            if len(parts) > 2:
-                yield self.err(body, 'N808', name=name)
-
-            suffix = parts[-1] if len(parts) > 1 else ''
-            if suffix and suffix != 'co' and suffix != 'contra':
-                yield self.err(body, 'N808', name=name)
-            elif keywords.get('covariant') and suffix != 'co':
-                yield self.err(body, 'N808', name=name)
-            elif keywords.get('contravariant') and suffix != 'contra':
-                yield self.err(body, 'N808', name=name)
-
-
     def visit_classdef(self, node, parents: Iterable, ignore=None):
         name = node.name
         if _ignored(name, ignore):
@@ -535,6 +500,44 @@ def function_variable_check(func, var_name):
         return 'N806'
 
 
+class TypeVarNameCheck(BaseASTCheck):
+    N808 = "type variable name '{name}' should use CapWords convention " \
+           "and an optional '_co' or '_contra' suffix"
+
+    def visit_module(self, node, parents: Iterable, ignore=None):
+        for body in node.body:
+            try:
+                if len(body.targets) != 1:
+                    continue
+                name = body.targets[0].id
+                func_name = body.value.func.id
+                args = [a.value for a in body.value.args]
+                keywords = {kw.arg: kw.value.value for kw in body.value.keywords}
+            except AttributeError:
+                continue
+
+            if func_name != "TypeVar" or _ignored(name, ignore):
+                continue
+
+            if len(args) == 0 or args[0] != name:
+                yield self.err(body, 'N808', name=name)
+
+            if not name[:1].isupper():
+                yield self.err(body, 'N808', name=name)
+
+            parts = name.split('_')
+            if len(parts) > 2:
+                yield self.err(body, 'N808', name=name)
+
+            suffix = parts[-1] if len(parts) > 1 else ''
+            if suffix and suffix != 'co' and suffix != 'contra':
+                yield self.err(body, 'N808', name=name)
+            elif keywords.get('covariant') and suffix != 'co':
+                yield self.err(body, 'N808', name=name)
+            elif keywords.get('contravariant') and suffix != 'contra':
+                yield self.err(body, 'N808', name=name)
+
+
 def _extract_names(assignment_target):
     """Yield assignment_target ids."""
     target_type = type(assignment_target)