Expand Y015 to cover assignments to negative numbers (#292)

CHANGELOG.md

@@ -9,6 +9,7 @@ Bugfixes:
   inside `class` blocks.
 * Expand Y035 to cover `__slots__` definitions as well as `__match_args__` and
   `__all__` definitions.
+* Expand Y015 so that errors are emitted for assignments to negative numbers.
 
 ## 22.8.2
 

pyi.py

@@ -900,6 +900,40 @@ def _check_for_typevarlike_assignments(
             else:
                 self.error(node, Y001.format(cls_name))
 
+    def _Y015_error(self, node: ast.Assign | ast.AnnAssign) -> None:
+        old_syntax = unparse(node)
+        copy_of_node = deepcopy(node)
+        copy_of_node.value = ast.Constant(value=...)
+        new_syntax = unparse(copy_of_node)
+        error_message = Y015.format(old_syntax=old_syntax, new_syntax=new_syntax)
+        self.error(node, error_message)
+
+    @staticmethod
+    def _Y015_violation_detected(node: ast.Assign | ast.AnnAssign) -> bool:
+        assignment = node.value
+
+        if isinstance(node, ast.AnnAssign):
+            if assignment and not isinstance(assignment, ast.Ellipsis):
+                return True
+            return False
+
+        if isinstance(assignment, (ast.Num, ast.Str, ast.Bytes)):
+            return True
+        if (
+            isinstance(assignment, ast.UnaryOp)
+            and isinstance(assignment.op, ast.USub)
+            and isinstance(assignment.operand, ast.Num)
+        ):
+            return True
+        if (
+            isinstance(assignment, (ast.Constant, ast.NameConstant))
+            and not isinstance(assignment, ast.Ellipsis)
+            and assignment.value is not None
+        ):
+            return True
+
+        return False
+
     def visit_Assign(self, node: ast.Assign) -> None:
         if self.in_function.active:
             # We error for unexpected things within functions separately.
@@ -927,6 +961,7 @@ def visit_Assign(self, node: ast.Assign) -> None:
             return
         assert isinstance(target, ast.Name)
         assignment = node.value
+
         if isinstance(assignment, ast.Call):
             function = assignment.func
             if _is_TypedDict(function):
@@ -936,15 +971,9 @@ def visit_Assign(self, node: ast.Assign) -> None:
                 self._check_for_typevarlike_assignments(
                     node=node, function=function, object_name=target_name
                 )
+            return
 
-        elif isinstance(assignment, (ast.Num, ast.Str, ast.Bytes)):
-            return self._Y015_error(node)
-
-        if (
-            isinstance(assignment, (ast.Constant, ast.NameConstant))
-            and not isinstance(assignment, ast.Ellipsis)
-            and assignment.value is not None
-        ):
+        if self._Y015_violation_detected(node):
             return self._Y015_error(node)
 
         if not is_special_assignment:
@@ -1063,24 +1092,23 @@ def visit_AnnAssign(self, node: ast.AnnAssign) -> None:
                 self.generic_visit(node)
             return
 
-        node_target, node_value = node.target, node.value
+        node_target = node.target
         if isinstance(node_target, ast.Name):
             target_name = node_target.id
             if _is_assignment_which_must_have_a_value(
                 target_name, in_class=self.in_class.active
             ):
                 with self.string_literals_allowed.enabled():
                     self.generic_visit(node)
-                if node_value is None:
+                if node.value is None:
                     self.error(node, Y035.format(var=target_name))
                 return
 
         if _is_TypeAlias(node_annotation) and isinstance(node_target, ast.Name):
             return self._check_typealias(node=node, alias_name=target_name)
 
         self.generic_visit(node)
-
-        if node_value and not isinstance(node_value, ast.Ellipsis):
+        if self._Y015_violation_detected(node):
             self._Y015_error(node)
 
     def _check_union_members(self, members: Sequence[ast.expr]) -> None:
@@ -1713,14 +1741,6 @@ def visit_arguments(self, node: ast.arguments) -> None:
             if not isinstance(default, ast.Ellipsis):
                 self.error(default, (Y014 if arg.annotation is None else Y011))
 
-    def _Y015_error(self, node: ast.Assign | ast.AnnAssign) -> None:
-        old_syntax = unparse(node)
-        copy_of_node = deepcopy(node)
-        copy_of_node.value = ast.Constant(value=...)
-        new_syntax = unparse(copy_of_node)
-        error_message = Y015.format(old_syntax=old_syntax, new_syntax=new_syntax)
-        self.error(node, error_message)
-
     def error(self, node: ast.AST, message: str) -> None:
         self.errors.append(Error(node.lineno, node.col_offset, message, PyiTreeChecker))
 

requirements-dev.txt

@@ -5,4 +5,4 @@ isort==5.10.1      # Must match .pre-commit-config.yaml
 flake8-bugbear==22.8.23
 flake8-noqa==1.2.9
 types-pyflakes==2.5.0
-ast_decompiler<1.0; python_version < '3.9'
+ast_decompiler>=0.7.0,<1.0; python_version < '3.9'

setup.py

@@ -40,7 +40,7 @@
     install_requires=[
         "flake8 >= 3.2.1, < 6.0.0",
         "pyflakes >= 2.1.1",
-        'ast-decompiler <1.0; python_version < "3.9"',
+        'ast-decompiler >= 0.7.0, < 1.0; python_version < "3.9"',
     ],
     test_suite="tests.test_pyi",
     classifiers=[

tests/attribute_annotations.pyi

@@ -12,6 +12,9 @@ field5 = 0  # type: int  # Y033 Do not use type comments in stubs (e.g. use "x:
 field6 = 0  # Y015 Bad default value. Use "field6 = ..." instead of "field6 = 0"
 field7 = b""  # Y015 Bad default value. Use "field7 = ..." instead of "field7 = b''"
 field8 = False  # Y015 Bad default value. Use "field8 = ..." instead of "field8 = False"
+field81 = -1  # Y015 Bad default value. Use "field81 = ..." instead of "field81 = -1"
+field82: float = -98.43  # Y015 Bad default value. Use "field82: float = ..." instead of "field82: float = -98.43"
+field83 = -42j  # Y015 Bad default value. Use "field83 = ..." instead of "field83 = -42j"
 
 # We don't want this one to trigger Y015 -- it's valid as a TypeAlias
 field9 = None  # Y026 Use typing_extensions.TypeAlias for type aliases, e.g. "field9: TypeAlias = None"
@@ -25,6 +28,7 @@ field14: Final = True
 field15: Final = ('a', 'b', 'c')
 field16: typing.Final = "foo"
 field17: typing_extensions.Final = "foo"
+field18: Final = -24j
 
 class Foo:
     field1: int