| from __future__ import annotations |
| |
| from typing import Callable |
| |
| from mypy.checker import TypeChecker |
| from mypy.nodes import TypeInfo |
| from mypy.plugin import FunctionContext, Plugin |
| from mypy.subtypes import is_proper_subtype |
| from mypy.types import ( |
| AnyType, |
| CallableType, |
| FunctionLike, |
| Instance, |
| NoneTyp, |
| ProperType, |
| TupleType, |
| Type, |
| UnionType, |
| get_proper_type, |
| get_proper_types, |
| ) |
| |
| |
| class ProperTypePlugin(Plugin): |
| """ |
| A plugin to ensure that every type is expanded before doing any special-casing. |
| |
| This solves the problem that we have hundreds of call sites like: |
| |
| if isinstance(typ, UnionType): |
| ... # special-case union |
| |
| But after introducing a new type TypeAliasType (and removing immediate expansion) |
| all these became dangerous because typ may be e.g. an alias to union. |
| """ |
| |
| def get_function_hook(self, fullname: str) -> Callable[[FunctionContext], Type] | None: |
| if fullname == "builtins.isinstance": |
| return isinstance_proper_hook |
| if fullname == "mypy.types.get_proper_type": |
| return proper_type_hook |
| if fullname == "mypy.types.get_proper_types": |
| return proper_types_hook |
| return None |
| |
| |
| def isinstance_proper_hook(ctx: FunctionContext) -> Type: |
| if len(ctx.arg_types) != 2 or not ctx.arg_types[1]: |
| return ctx.default_return_type |
| |
| right = get_proper_type(ctx.arg_types[1][0]) |
| for arg in ctx.arg_types[0]: |
| if ( |
| is_improper_type(arg) or isinstance(get_proper_type(arg), AnyType) |
| ) and is_dangerous_target(right): |
| if is_special_target(right): |
| return ctx.default_return_type |
| ctx.api.fail( |
| "Never apply isinstance() to unexpanded types;" |
| " use mypy.types.get_proper_type() first", |
| ctx.context, |
| ) |
| ctx.api.note( # type: ignore[attr-defined] |
| "If you pass on the original type" |
| " after the check, always use its unexpanded version", |
| ctx.context, |
| ) |
| return ctx.default_return_type |
| |
| |
| def is_special_target(right: ProperType) -> bool: |
| """Whitelist some special cases for use in isinstance() with improper types.""" |
| if isinstance(right, FunctionLike) and right.is_type_obj(): |
| if right.type_object().fullname == "builtins.tuple": |
| # Used with Union[Type, Tuple[Type, ...]]. |
| return True |
| if right.type_object().fullname in ( |
| "mypy.types.Type", |
| "mypy.types.ProperType", |
| "mypy.types.TypeAliasType", |
| ): |
| # Special case: things like assert isinstance(typ, ProperType) are always OK. |
| return True |
| if right.type_object().fullname in ( |
| "mypy.types.UnboundType", |
| "mypy.types.TypeVarLikeType", |
| "mypy.types.TypeVarType", |
| "mypy.types.UnpackType", |
| "mypy.types.TypeVarTupleType", |
| "mypy.types.ParamSpecType", |
| "mypy.types.Parameters", |
| "mypy.types.RawExpressionType", |
| "mypy.types.EllipsisType", |
| "mypy.types.StarType", |
| "mypy.types.TypeList", |
| "mypy.types.CallableArgument", |
| "mypy.types.PartialType", |
| "mypy.types.ErasedType", |
| "mypy.types.DeletedType", |
| "mypy.types.RequiredType", |
| ): |
| # Special case: these are not valid targets for a type alias and thus safe. |
| # TODO: introduce a SyntheticType base to simplify this? |
| return True |
| elif isinstance(right, TupleType): |
| return all(is_special_target(t) for t in get_proper_types(right.items)) |
| return False |
| |
| |
| def is_improper_type(typ: Type) -> bool: |
| """Is this a type that is not a subtype of ProperType?""" |
| typ = get_proper_type(typ) |
| if isinstance(typ, Instance): |
| info = typ.type |
| return info.has_base("mypy.types.Type") and not info.has_base("mypy.types.ProperType") |
| if isinstance(typ, UnionType): |
| return any(is_improper_type(t) for t in typ.items) |
| return False |
| |
| |
| def is_dangerous_target(typ: ProperType) -> bool: |
| """Is this a dangerous target (right argument) for an isinstance() check?""" |
| if isinstance(typ, TupleType): |
| return any(is_dangerous_target(get_proper_type(t)) for t in typ.items) |
| if isinstance(typ, CallableType) and typ.is_type_obj(): |
| return typ.type_object().has_base("mypy.types.Type") |
| return False |
| |
| |
| def proper_type_hook(ctx: FunctionContext) -> Type: |
| """Check if this get_proper_type() call is not redundant.""" |
| arg_types = ctx.arg_types[0] |
| if arg_types: |
| arg_type = get_proper_type(arg_types[0]) |
| proper_type = get_proper_type_instance(ctx) |
| if is_proper_subtype(arg_type, UnionType.make_union([NoneTyp(), proper_type])): |
| # Minimize amount of spurious errors from overload machinery. |
| # TODO: call the hook on the overload as a whole? |
| if isinstance(arg_type, (UnionType, Instance)): |
| ctx.api.fail("Redundant call to get_proper_type()", ctx.context) |
| return ctx.default_return_type |
| |
| |
| def proper_types_hook(ctx: FunctionContext) -> Type: |
| """Check if this get_proper_types() call is not redundant.""" |
| arg_types = ctx.arg_types[0] |
| if arg_types: |
| arg_type = arg_types[0] |
| proper_type = get_proper_type_instance(ctx) |
| item_type = UnionType.make_union([NoneTyp(), proper_type]) |
| ok_type = ctx.api.named_generic_type("typing.Iterable", [item_type]) |
| if is_proper_subtype(arg_type, ok_type): |
| ctx.api.fail("Redundant call to get_proper_types()", ctx.context) |
| return ctx.default_return_type |
| |
| |
| def get_proper_type_instance(ctx: FunctionContext) -> Instance: |
| checker = ctx.api |
| assert isinstance(checker, TypeChecker) |
| types = checker.modules["mypy.types"] |
| proper_type_info = types.names["ProperType"] |
| assert isinstance(proper_type_info.node, TypeInfo) |
| return Instance(proper_type_info.node, []) |
| |
| |
| def plugin(version: str) -> type[ProperTypePlugin]: |
| return ProperTypePlugin |