Add error-code for truthy-iterable
#13762
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@hauntsaninja This is related to #13686, this time for |
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Pushed a new commit to disable the error-code by default. That should minimize the impact of the PR. |
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@JelleZijlstra Would you mind taking a look? The actual code change is quite small but I think it will be an improvement never the less. The PR is ready from my POV. |
| @@ -153,6 +153,10 @@ def with_additional_msg(self, info: str) -> ErrorMessage: | |||
| FUNCTION_ALWAYS_TRUE: Final = ErrorMessage( | |||
| "Function {} could always be true in boolean context", code=codes.TRUTHY_FUNCTION | |||
| ) | |||
| ITERABLE_ALWAYS_TRUE: Final = ErrorMessage( | |||
| "{} which can always be true in boolean context. Consider using {} instead.", | |||
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This message reads a bit weird to me but I guess it's consistent with the other ALWAYS_TRUE messages.
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On its own, I agree. It gets better once the variables are inserted. E.g.
"var" has type "Iterable[str]" which can always be true in boolean context.
Consider using "Collection[str]" instead. [truthy-iterable]
docs/source/error_code_list2.rst
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| This is similar in concept to ensuring that an expression's type implements an expected interface (e.g. ``Sized``), | ||
| except that attempting to invoke an undefined method (e.g. ``__len__``) results in an error, | ||
| while attempting to evaluate an object in boolean context without a concrete implementation results in a truthy value. |
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I don't understand what this sentence is trying to say. What is "this" exactly?
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As best as I can tell, "this" refers to the check itself and the fact that it doesn't highlight a concrete issue but rather only a potential one.
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According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉 |
Add a separate error code for
truthy-iterable.Iterabledoes not implement__len__, so passing aGeneratorwould always evaluate totrue. SuggestCollectionas alternative.In most cases this isn't an issue as the function is often called with
listanyway. However, the dedicated check can pinpoint subtle errors that might get unnoticed otherwise.