Adds "no __author__" validator (#7)

* Adds "no __author__" validator

* Fixes a typo in the comment

* Fixes import order

* Fixes flake8 violations

* Fixes mypy violation

tests/fixtures/wrong_variable.py

@@ -4,9 +4,15 @@
 This file contains all broken variable names.
 """
 
+__author__ = 'John Doe'  # error here
+
 x = 1  # error here
 
 
+def fixture():
+    __author__ = 'John Doe'  # no error, because not module metadata
+
+
 def check_function_args(data, t, *a, **vals):  # 4 errors here
     result = data + t  # error here for `result`
     return result
@@ -41,3 +47,6 @@ def __init__(self, value):  # error here
 
 val = Fixture()  # error here
 print(val.var)  # no error here
+
+if val:
+    __author__ = 'John'  # no error here since it's a rare use of module meta

tests/test_checkers/test_wrong_variable.py

@@ -18,3 +18,4 @@ def test_wrong_variables_in_fixture(absolute_path):
     assert stdout.count(b'WPS122') == 3
     assert stdout.count(b'WPS123') == 2
     assert stdout.count(b'WPS124') == 1
+    assert stdout.count(b'WPS126') == 1

wemake_python_styleguide/checker.py

@@ -15,6 +15,7 @@
 )
 from wemake_python_styleguide.visitors.wrong_nested import WrongNestedVisitor
 from wemake_python_styleguide.visitors.wrong_variable import (
+    WrongModuleMetadata,
     WrongVariableVisitor,
 )
 
@@ -42,6 +43,7 @@ def __init__(self, tree: Module, filename: str = '-') -> None:
             WrongNestedVisitor,
             ComplexityVisitor,
             WrongVariableVisitor,
+            WrongModuleMetadata,
         )
 
     def run(self) -> Generator[tuple, None, None]:

wemake_python_styleguide/constants.py

@@ -25,6 +25,10 @@
     '__import__',
 ))
 
+BAD_MODULE_METADATA_VARIABLES = frozenset((
+    '__author__',
+))
+
 BAD_VARIABLE_NAMES = frozenset((
     'data',
     'result',

wemake_python_styleguide/errors.py

@@ -87,6 +87,11 @@ class TooShortAttributeNameViolation(BaseStyleViolation):
     _code = 'WPS125'
 
 
+class WrongModuleMetadataViolation(BaseStyleViolation):
+    _error_tmpl = '{} Found wrong metadata variable {}'
+    _code = 'WPS126'
+
+
 class LocalFolderImportViolation(BaseStyleViolation):
     _error_tmpl = '{} Found local folder import "{}"'
     _code = 'WPS130'

wemake_python_styleguide/visitors/wrong_variable.py

@@ -2,13 +2,17 @@
 
 import ast
 
-from wemake_python_styleguide.constants import BAD_VARIABLE_NAMES
+from wemake_python_styleguide.constants import (
+    BAD_MODULE_METADATA_VARIABLES,
+    BAD_VARIABLE_NAMES,
+)
 from wemake_python_styleguide.errors import (
     TooShortArgumentNameViolation,
     TooShortAttributeNameViolation,
     TooShortVariableNameViolation,
     WrongArgumentNameViolation,
     WrongAttributeNameViolation,
+    WrongModuleMetadataViolation,
     WrongVariableNameViolation,
 )
 from wemake_python_styleguide.helpers.variables import (
@@ -94,3 +98,20 @@ def visit_Name(self, node: ast.Name):
                 )
 
         self.generic_visit(node)
+
+
+class WrongModuleMetadata(BaseNodeVisitor):
+    """This class finds wrong metadata information of a module."""
+
+    def visit_Assign(self, node: ast.Assign):
+        """Used to find the bad metadata variable names."""
+        node_parent = getattr(node, 'parent')
+        if not isinstance(node_parent, ast.Module):
+            return
+
+        for target_node in node.targets:
+            target_node_id = getattr(target_node, 'id')
+            if target_node_id in BAD_MODULE_METADATA_VARIABLES:
+                self.add_error(
+                    WrongModuleMetadataViolation(node, text=target_node_id),
+                )