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Lambda expression confuses branch measurement #90

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nedbat opened this issue Sep 12, 2010 · 6 comments
Closed

Lambda expression confuses branch measurement #90

nedbat opened this issue Sep 12, 2010 · 6 comments
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branch bug Something isn't working

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@nedbat
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nedbat commented Sep 12, 2010

A line like this:

    fn = make_sortable or (lambda x: x) 

is marked as being a branch with a missing jump to "exit", maybe only if the lambda isn't used.


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nedbat commented May 27, 2011

Original comment by Carl Meyer (Bitbucket: carljm, GitHub: carljm)


I can verify that, at least in my case, the missing jump to exit disappeared when I ensured the lambda was used during the test run. Seems to me this could be considered useful coverage information, not a bug -- if anything, the branch-coverage report should special-case this to display a more informative label on the line?

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nedbat commented Jan 15, 2013

A particularly confusing form of this bug:

OPERATIONS = [
    operator.add,
    operator.sub,
    lambda x: 2*x,
    operator.mul,
]

The "OPERATIONS = " line will have a missed branch to "exit" if the lambda expression is never executed.

@nedbat
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nedbat commented Jan 2, 2016

Bug #460 is related to this.

@nedbat
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nedbat commented Jan 6, 2016

Perhaps the best we can do here is to report it as "Missed lambda" instead of "missed branch to exit."

@nedbat
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nedbat commented May 7, 2016

It's not as good as I would like, but as of now, the HTML shows "3 ↛ exit", and the hover text reads "line 6 didn't finish the lambda on line 6".

I think this provides enough information to the reader. Getting more precise would require collecting data differently, to distinguish the line 6 execution during building the list, from line 6 execution during running the lambda. We can distinguish them based on the co_firstlineno of the frame, but we don't have a way to record that data as we go.

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nedbat commented Aug 30, 2017

Original comment by Daniel Hahler (Bitbucket: blueyed, GitHub: blueyed)


Could this be reflected in the xml report, too?

@nedbat nedbat closed this as completed Aug 30, 2017
@nedbat nedbat added major bug Something isn't working branch labels Jun 23, 2018
agronholm pushed a commit to agronholm/coveragepy that referenced this issue Aug 16, 2020
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