Suggest codemod for --no-implicit-optional (#13747)

mypy/checker.py

@@ -1262,13 +1262,27 @@ def check_default_args(self, item: FuncItem, body_is_trivial: bool) -> None:
  msg += f"tuple argument {name[12:]}"
  else:
  msg += f'argument "{name}"'
+ if (
+ not self.options.implicit_optional
+ and isinstance(arg.initializer, NameExpr)
+ and arg.initializer.fullname == "builtins.None"
+ ):
+ notes = [
+ "PEP 484 prohibits implicit Optional. "
+ "Accordingly, mypy has changed its default to no_implicit_optional=True",
+ "Use https://github.com/hauntsaninja/no_implicit_optional to automatically "
+ "upgrade your codebase",
+ ]
+ else:
+ notes = None
  self.check_simple_assignment(
  arg.variable.type,
  arg.initializer,
  context=arg.initializer,
  msg=ErrorMessage(msg, code=codes.ASSIGNMENT),
  lvalue_name="argument",
  rvalue_name="default",
+ notes=notes,
  )
 
  def is_forward_op_method(self, method_name: str) -> bool:
@@ -3739,6 +3753,8 @@ def check_simple_assignment(
  msg: ErrorMessage = message_registry.INCOMPATIBLE_TYPES_IN_ASSIGNMENT,
  lvalue_name: str = "variable",
  rvalue_name: str = "expression",
+ *,
+ notes: list[str] | None = None,
  ) -> Type:
  if self.is_stub and isinstance(rvalue, EllipsisExpr):
  # '...' is always a valid initializer in a stub.
@@ -3763,6 +3779,7 @@ def check_simple_assignment(
  msg,
  f"{rvalue_name} has type",
  f"{lvalue_name} has type",
+ notes=notes,
  )
  return rvalue_type
 
@@ -5666,6 +5683,7 @@ def check_subtype(
  subtype_label: str | None = None,
  supertype_label: str | None = None,
  *,
+ notes: list[str] | None = None,
  code: ErrorCode | None = None,
  outer_context: Context | None = None,
  ) -> bool:
@@ -5681,6 +5699,7 @@ def check_subtype(
  subtype_label: str | None = None,
  supertype_label: str | None = None,
  *,
+ notes: list[str] | None = None,
  outer_context: Context | None = None,
  ) -> bool:
  ...
@@ -5694,6 +5713,7 @@ def check_subtype(
  subtype_label: str | None = None,
  supertype_label: str | None = None,
  *,
+ notes: list[str] | None = None,
  code: ErrorCode | None = None,
  outer_context: Context | None = None,
  ) -> bool:
@@ -5714,7 +5734,7 @@ def check_subtype(
  return False
  extra_info: list[str] = []
  note_msg = ""
- notes: list[str] = []
+ notes = notes or []
  if subtype_label is not None or supertype_label is not None:
  subtype_str, supertype_str = format_type_distinctly(orig_subtype, orig_supertype)
  if subtype_label is not None:
@@ -5725,7 +5745,7 @@ def check_subtype(
  outer_context or context, subtype, supertype, supertype_str
  )
  if isinstance(subtype, Instance) and isinstance(supertype, Instance):
- notes = append_invariance_notes([], subtype, supertype)
+ notes = append_invariance_notes(notes, subtype, supertype)
  if extra_info:
  msg = msg.with_additional_msg(" (" + ", ".join(extra_info) + ")")
 

test-data/unit/check-optional.test

@@ -136,7 +136,9 @@ f(None)
 
 [case testNoInferOptionalFromDefaultNone]
 # flags: --no-implicit-optional
-def f(x: int = None) -> None: # E: Incompatible default for argument "x" (default has type "None", argument has type "int")
+def f(x: int = None) -> None: # E: Incompatible default for argument "x" (default has type "None", argument has type "int") \
+ # N: PEP 484 prohibits implicit Optional. Accordingly, mypy has changed its default to no_implicit_optional=True \
+ # N: Use https://github.com/hauntsaninja/no_implicit_optional to automatically upgrade your codebase
  pass
 [out]
 
@@ -151,7 +153,9 @@ f(None)
 
 [case testNoInferOptionalFromDefaultNoneComment]
 # flags: --no-implicit-optional
-def f(x=None): # E: Incompatible default for argument "x" (default has type "None", argument has type "int")
+def f(x=None): # E: Incompatible default for argument "x" (default has type "None", argument has type "int") \
+ # N: PEP 484 prohibits implicit Optional. Accordingly, mypy has changed its default to no_implicit_optional=True \
+ # N: Use https://github.com/hauntsaninja/no_implicit_optional to automatically upgrade your codebase
  # type: (int) -> None
  pass
 [out]