Add --disallow-str-iteration flag #20577
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| s = "hello" | ||
| for ch in s: # error: Iterating over "str" is disallowed | ||
| print(ch) | ||
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Maybe add an example with iter(s) to show that's OK.
mypy/typeshed/stdlib/builtins.pyi
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| def __getitem__(self, i: int, /) -> _T_co: ... | ||
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| @overload | ||
| def iter(object: str, /) -> Iterable[str]: ... |
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This needs to be in a patch file, or it will be overwritten next time we sync typeshed. Look for similar patch files in the repo (there are a few related to LiteralString).
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Diff from mypy_primer, showing the effect of this PR on open source code: meson (https://github.com/mesonbuild/meson)
+ mesonbuild/compilers/cuda.py:249:34: error: No overload variant of "next" matches argument type "Iterable[str]" [call-overload]
+ mesonbuild/compilers/cuda.py:249:34: note: Possible overload variants:
+ mesonbuild/compilers/cuda.py:249:34: note: def [_T] next(SupportsNext[_T], /) -> _T
+ mesonbuild/compilers/cuda.py:249:34: note: def [_T, _VT] next(SupportsNext[_T], _VT, /) -> _T | _VT
altair (https://github.com/vega/altair)
+ tools/vega_expr.py:822: error: No overload variant of "next" matches argument type "Iterable[str]" [call-overload]
+ tools/vega_expr.py:822: note: Possible overload variants:
+ tools/vega_expr.py:822: note: def [_T] next(SupportsNext[_T], /) -> _T
+ tools/vega_expr.py:822: note: def [_T, _VT] next(SupportsNext[_T], _VT, /) -> _T | _VT
cki-lib (https://gitlab.com/cki-project/cki-lib)
+ cki_lib/cki_pipeline.py:537: error: No overload variant of "next" matches argument types "Iterable[str]", "None" [call-overload]
+ cki_lib/cki_pipeline.py:537: note: Possible overload variants:
+ cki_lib/cki_pipeline.py:537: note: def [_T] next(SupportsNext[_T], /) -> _T
+ cki_lib/cki_pipeline.py:537: note: def [_T, _VT] next(SupportsNext[_T], _VT, /) -> _T | _VT
ibis (https://github.com/ibis-project/ibis)
+ ibis/expr/types/generic.py:1785: error: No overload variant of "next" matches argument type "Iterable[str]" [call-overload]
+ ibis/expr/types/generic.py:1785: note: Possible overload variants:
+ ibis/expr/types/generic.py:1785: note: def [_T] next(SupportsNext[_T], /) -> _T
+ ibis/expr/types/generic.py:1785: note: def [_T, _VT] next(SupportsNext[_T], _VT, /) -> _T | _VT
apprise (https://github.com/caronc/apprise)
+ apprise/config/base.py:1509: note: def iter(str, /) -> Iterable[str]
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| def is_str_iteration_type(self, typ: Type) -> bool: | ||
| typ = get_proper_type(typ) | ||
| if isinstance(typ, LiteralType): |
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wonder if we should do this for subtypes of str too and do something like an is_proper_subtype() check with str.
| "collections.abc.Collection", | ||
| "typing.Collection", | ||
| ): | ||
| # `str` doesn't conform to the `Collection` protocol, but we don't want to show that as the reason for the error. |
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Isn't the discrepancy actually on Container? So we should maybe do this for any subclass of Container.
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Fixes #11001
Related to typing python/typing#256