Fix Y053 false positives inside Literal and Annotated slices (#497)

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Change Log
 
+## Unreleased
+
+Bugfixes
+* Don't emit Y053 for long strings inside `Literal` slices or
+  metadata strings inside `Annotated` slices.
+
 ## 24.6.0
 
 Bugfixes

ERRORCODES.md

@@ -66,7 +66,7 @@ The following warnings are currently emitted by default:
 | <a id="Y050" href="#Y050">Y050</a> | Prefer `typing_extensions.Never` over `typing.NoReturn` for argument annotations. | Style
 | <a id="Y051" href="#Y051">Y051</a> | Y051 detects redundant unions between `Literal` types and builtin supertypes. For example, `Literal[5]` is redundant in the union `int \| Literal[5]`, and `Literal[True]` is redundant in the union `Literal[True] \| bool`. | Redundant code
 | <a id="Y052" href="#Y052">Y052</a> | Y052 disallows assignments to constant values where the assignment does not have a type annotation. For example, `x = 0` in the global namespace is ambiguous in a stub, as there are four different types that could be inferred for the variable `x`: `int`, `Final[int]`, `Literal[0]`, or `Final[Literal[0]]`. Enum members are excluded from this check, as are various special assignments such as `__all__` and `__match_args__`. | Correctness
-| <a id="Y053" href="#Y053">Y053</a> | Only string and bytes literals <=50 characters long are permitted. | Style
+| <a id="Y053" href="#Y053">Y053</a> | Only string and bytes literals <=50 characters long are permitted. (There are some exceptions, such as `Literal` subscripts, metadata strings inside `Annotated` subscripts, and strings passed to `@deprecated`.) | Style
 | <a id="Y054" href="#Y054">Y054</a> | Only numeric literals with a string representation <=10 characters long are permitted. | Style
 | <a id="Y055" href="#Y055">Y055</a> | Unions of the form `type[X] \| type[Y]` can be simplified to `type[X \| Y]`. Similarly, `Union[type[X], type[Y]]` can be simplified to `type[Union[X, Y]]`. | Style
 | <a id="Y056" href="#Y056">Y056</a> | Do not call methods such as `.append()`, `.extend()` or `.remove()` on `__all__`. Different type checkers have varying levels of support for calling these methods on `__all__`. Use `+=` instead, which is known to be supported by all major type checkers. | Correctness

pyi.py

@@ -1563,7 +1563,8 @@ def _visit_typing_Literal(self, node: ast.Subscript) -> None:
                 suggestion = f"Literal[{new_literal_slice}] | None"
                 self.error(analysis.none_members[0], Y061.format(suggestion=suggestion))
 
-        self.visit(node.slice)
+        with self.long_strings_allowed.enabled():
+            self.visit(node.slice)
 
     def _visit_slice_tuple(self, node: ast.Tuple, parent: str | None) -> None:
         if parent == "Union":
@@ -1573,7 +1574,7 @@ def _visit_slice_tuple(self, node: ast.Tuple, parent: str | None) -> None:
             # Allow literals, except in the first argument
             if len(node.elts) > 1:
                 self.visit(node.elts[0])
-                with self.string_literals_allowed.enabled():
+                with self.string_literals_allowed.enabled(), self.long_strings_allowed.enabled():
                     for elt in node.elts[1:]:
                         self.visit(elt)
             else:

tests/defaults.pyi

@@ -1,6 +1,7 @@
 import math
 import os
 import sys
+from typing import Annotated, Literal, TypeAlias
 
 import _typeshed
 from _typeshed import SupportsRead, SupportsWrite, sentinel
@@ -84,3 +85,10 @@ def f40(x: int, /) -> None: ...
 def f41(x: int, /, y: "int") -> None: ...  # Y020 Quoted annotations should never be used in stubs
 def f42(x: str = "y", /) -> None: ...
 def f43(x: str = os.pathsep, /) -> None: ...  # Y011 Only simple default values allowed for typed arguments
+
+# Long strings inside `Literal` or `Annotated` slices are okay
+def f44(x: Literal["loooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooong"]) -> None: ...
+def f55(x: Annotated[str, "metadataaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"]) -> None: ...
+
+X: TypeAlias = Literal["llllllllllllllllllllllllllonggggggggggggggggggggggggggggggggggggggggg"]
+Y: TypeAlias = Annotated[int, "verrrrrrrrrrrrrrrrrrrry looooooooooooooongggggggggggggggggggggggggggggggggggg"]

tests/pep695_py312.pyi

@@ -3,7 +3,16 @@
 
 import typing
 from collections.abc import Iterator
-from typing import Any, NamedTuple, NoReturn, Protocol, Self, TypedDict
+from typing import (
+    Annotated,
+    Any,
+    Literal,
+    NamedTuple,
+    NoReturn,
+    Protocol,
+    Self,
+    TypedDict,
+)
 
 type lowercase_alias = str | int  # Y042 Type aliases should use the CamelCase naming convention
 type _LooksLikeATypeVarT = str | int  # Y043 Bad name for a type alias (the "T" suffix implies a TypeVar)
@@ -66,3 +75,6 @@ class _UnusedPEP695Protocol[T](Protocol):  # Y046 Protocol "_UnusedPEP695Protoco
 
 class _UnusedPEP695TypedDict[T](TypedDict):  # Y049 TypedDict "_UnusedPEP695TypedDict" is not used
     x: T
+
+type X = Literal["Y053 will not be emitted here despite it being a very long string literal, because it is inside a `Literal` slice"]
+type Y = Annotated[int, "look at me, very long string literal, but it's okay because it's an `Annotated` metadata string"]