1948 Add Specifying Encoder Rule

CHANGELOG.md

@@ -16,7 +16,13 @@ Semantic versioning in our case means:
   But, in the future we might change the configuration names / logic,
   change the client facing API, change code conventions signigicantly, etc.
 
-
+## 0.16.0
+
+### Features
+
+- Forbid using open without specifying encoding.
+
+
 ## 0.15.3 WIP
 
 ### Bugfixes

docs/conf.py

@@ -21,7 +21,7 @@
 # -- Project information -----------------------------------------------------
 
 def _get_project_meta():
-    with open('../pyproject.toml') as pyproject:
+    with open('../pyproject.toml', encoding=None) as pyproject:
         file_contents = pyproject.read()
 
     return tomlkit.parse(file_contents)['tool']['poetry']

scripts/check_generic_visit.py

@@ -33,7 +33,7 @@
     my_print('"self.generic_visit(node)" should be last statement here:')
 
     for fn, line in matches:
-        with open(fn, 'r') as fp:
+        with open(fn, 'r', encoding='utf-8-sig') as fp:
             source = fp.read()
             lines = source.splitlines()
             highlighted = highlight(

tests/fixtures/noqa/noqa.py

@@ -381,7 +381,7 @@ def function_with_wrong_yield():
 for literal in bad_concatenation:  # noqa: WPS327, WPS328
     continue
 
-with open(bad_concatenation):  # noqa: WPS328
+with open(bad_concatenation):  # noqa: WPS328, WPS467
     pass  # noqa: WPS420
 
 
@@ -404,7 +404,7 @@ def some_other_function():
 string_concat = 'a' + 'b'  # noqa: WPS336
 
 my_print(one == 'a' or one == 'b')  # noqa: WPS514
-file_obj = open('filaname.py')  # noqa: WPS515
+file_obj = open('filaname.py')  # noqa: WPS515, WPS467
 my_print(type(file_obj) == int)  # noqa: WPS516
 
 my_print(*[], **{'@': 1})  # noqa: WPS517, WPS445
@@ -549,7 +549,7 @@ def bad_default_values(
 for nodes[0] in (1, 2, 3):  # noqa: WPS405
     anti_wps428 = 1
 
-with open('some') as MyBadException.custom:  # noqa: WPS406
+with open('some') as MyBadException.custom:  # noqa: WPS406, WPS467
     anti_wps428 = 1
 
 

tests/test_checker/test_noqa.py

@@ -246,6 +246,7 @@
     'WPS464': 0,  # logically unacceptable.
     'WPS465': 1,
     'WPS466': 0,  # defined in version specific table.
+    'WPS467': 3,
 
     'WPS500': 1,
     'WPS501': 1,

tests/test_visitors/test_ast/test_attributes/test_open_encoding.py

@@ -0,0 +1,88 @@
+import pytest
+
+from wemake_python_styleguide.violations.best_practices import (
+    UnspecifiedEncodingViolation,
+)
+from wemake_python_styleguide.visitors.ast.attributes import EncodingVisitor
+
+unspecified_encoding_with = """
+with open('filename.txt') as fd:
+    fd.read()
+"""
+
+specified_encoding_with = """
+with open('filename.txt', encoding='ascii') as fd:
+    fd.read()
+"""
+
+unspecified_encoding_assign = """
+file = open('filename.txt', 'r')
+"""
+
+specified_encoding_assign = """
+file = open('filename.txt', 'r', encoding='utf8')
+"""
+
+specified_encoding_with_none = """
+with open('filename.txt', encoding=None) as fd:
+    fd.read()
+"""
+
+unspecified_encoding_with_multiple = """
+with open('filename.txt', 'w', -1) as fd:
+    fd.read()
+"""
+
+specified_encoding_with_multiple = """
+with open('filename.txt', 'w', -1, None) as fd:
+    fd.read()
+"""
+
+unspecified_encoding_assign_multiple = """
+file = open('filename.txt', 'w', -1)
+"""
+
+specified_encoding_assign_multiple = """
+file = open('filename.txt', 'w', -1, None)
+"""
+
+
+@pytest.mark.parametrize('code', [
+    unspecified_encoding_with,
+    unspecified_encoding_assign,
+    unspecified_encoding_with_multiple,
+    unspecified_encoding_assign_multiple,
+])
+def test_unspecified_encoding(
+    assert_errors,
+    code,
+    default_options,
+    parse_ast_tree,
+):
+    """Testing open encoding is unspecified."""
+    tree = parse_ast_tree(code)
+    visitor = EncodingVisitor(default_options, tree=tree)
+    visitor.run()
+
+    assert_errors(visitor, [UnspecifiedEncodingViolation])
+
+
+@pytest.mark.parametrize('code', [
+    specified_encoding_with,
+    specified_encoding_assign,
+    specified_encoding_with_none,
+    specified_encoding_with_multiple,
+    specified_encoding_assign_multiple,
+])
+def test_specified_encoding(
+    assert_errors,
+    code,
+    default_options,
+    parse_ast_tree,
+):
+    """Testing open encoding is specified."""
+    tree = parse_ast_tree(code)
+    visitor = EncodingVisitor(default_options, tree=tree)
+    visitor.run()
+
+    assert_errors(visitor, [])

wemake_python_styleguide/presets/types/tree.py

@@ -46,6 +46,7 @@
     loops.SyncForLoopVisitor,
 
     attributes.WrongAttributeVisitor,
+    attributes.EncodingVisitor,
     annotations.WrongAnnotationVisitor,
 
     functions.WrongFunctionCallVisitor,

wemake_python_styleguide/violations/best_practices.py

@@ -83,6 +83,7 @@
    EmptyCommentViolation
    BitwiseAndBooleanMixupViolation
    NewStyledDecoratorViolation
+   UnspecifiedEncodingViolation
 
 Best practices
 --------------
@@ -154,6 +155,7 @@
 .. autoclass:: EmptyCommentViolation
 .. autoclass:: BitwiseAndBooleanMixupViolation
 .. autoclass:: NewStyledDecoratorViolation
+.. autoclass:: UnspecifiedEncodingViolation
 
 """
 
@@ -2572,3 +2574,31 @@ def my_function(): ...
 
     error_template = 'Found new-styled decorator'
     code = 466
+
+
+@final
+class UnspecifiedEncodingViolation(ASTViolation):
+    """
+    Forbid using open without specifying encoding.
+
+    Reasoning:
+        Inspired by https://www.python.org/dev/peps/pep-0597/
+        Not specifying the encoding could be considered a bug.
+        Developers using macOS or Linux may forget that the
+        default encoding is not always UTF-8.
+
+    Solution:
+        Specify the encoding in open.
+
+    Example:
+        # Correct:
+        open('filename.txt', encoding='utf8')
+
+        # Wrong:
+        with open('filename.txt')
+
+    .. versionadded:: 0.16.0
+    """
+
+    error_template = 'Found unespecified encoding'
+    code = 467

wemake_python_styleguide/visitors/ast/attributes.py

@@ -1,11 +1,13 @@
 import ast
-from typing import ClassVar, FrozenSet
+from typing import ClassVar, FrozenSet, List
 
 from typing_extensions import final
 
 from wemake_python_styleguide.logic.naming import access
+from wemake_python_styleguide.logic.tree.functions import given_function_called
 from wemake_python_styleguide.violations.best_practices import (
     ProtectedAttributeViolation,
+    UnspecifiedEncodingViolation,
 )
 from wemake_python_styleguide.violations.oop import (
     DirectMagicAttributeAccessViolation,
@@ -73,3 +75,27 @@ def _check_magic_attribute(self, node: ast.Attribute) -> None:
                 self._ensure_attribute_type(
                     node, DirectMagicAttributeAccessViolation,
                 )
+
+
+@final
+class EncodingVisitor(BaseNodeVisitor):
+    """Check if open function has the encoding parameter."""
+
+    def visit_Call(self, node: ast.Call) -> None:
+        """Visit calls and finds if it is an open function."""
+        if given_function_called(node, {'open'}):
+            is_keyword = self._check_keywords(node.keywords)
+            is_positional = self._check_args(node.args)
+
+            if not is_positional and not is_keyword:
+                self.add_violation(UnspecifiedEncodingViolation(node))
+
+        self.generic_visit(node)
+
+    def _check_keywords(self, keywords: List[ast.keyword]) -> bool:
+        """Check if there is an encoding parameter."""
+        return any(keyword.arg == 'encoding' for keyword in keywords)
+
+    def _check_args(self, positionals: List[ast.expr]) -> bool:
+        """Check if there is an encoding parameter."""
+        return len(positionals) > 3 and isinstance(positionals[3], ast.Constant)