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sobolevn
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Sep 24, 2025
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The question is: does this function actually return None? Or is it a repr bug?
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weirder and weirder
>>> from hypothesis.internal.lambda_sources import lambda_description
>>> lambda_description(lambda *args, **kwargs: None)
'lambda *args, **kwargs: None'
>>> lambda_description(lambda *args: None)
'lambda *args: <unknown>'
>>> lambda_description(lambda: None)
'lambda: <unknown>'I keep looking
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Looks like the repr of lambdas was changed in HypothesisWorks/hypothesis#4500. Afaics, they used to always use <unknown>, but now they refine the lambda body string where possible. I think this should be a harmless change for us.
(Found this via the changelog for 6.137.3
This patch makes the stringification of lambdas, and as a result
certain automatic filter rewriting operations, more robust. This fixes
issue https://github.com/HypothesisWorks/hypothesis/issues/4498, where a lambda was mistakenly identified as the identity
operator due to "inspect.getsource()" only returning the first line of
the lambda definition.
As a result, the "repr" of strategies filtered or mapped by lambda
functions may change slightly.
)
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I have made things!
@pradeep90 hey! Your code is broken :) Can you validate it?
In hypothesis==6.137.2, this code produced the following output:
Whereas in hypothesis==6.140.2, the output is already:
So this is indeed a direct change in the library itself.
Checklist
CHANGELOG.mdRelated issues
Refs #2262
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