exception-branch coverage view

[spaceone]

It would be very nice, if coveragepy would support another view, which shows every line where an exception was (not) raised.

There are often lines, where a test case want to test the error handling and expects a exception to be raised which is not catched. This would help to verify that the line did raise an exception.

Similar to branch coverage, which is displayed in yellow, exception coverage could be printed in blue.

[nedbat]

Thanks for the idea. I'm not sure how to do this. Coverage needs two things: to measure what happened, and to statically analyze what could have happened. I think we can measure where exceptions are raised, but I don't know how to analyze code to see where exceptions could have happened. In theory, any line could raise an exception, but in practice that's not what people mean by "could raise an exception."

Do you have an idea about how to know where the exceptions might happen?

[spaceone]

I thought that every line could raise an exception and meant exactly this.
So we mark every line where a exception actually happened (blue). All others are ignored. Or vice versa.
It shouldn't really go into the coverage percentage.
Just a marker: Okay, line XXX raised any exception - my test worked.
Maybe I would also do the work to write something which greps the line numbers of my code where I expect exceptions and compare this.
What I wouldn't want is a marker: # pragma: raises.

I wouldn't introspect e.g. functions, which exceptions they possibly raise.
This doesn't even work. Nice would be if Python would allow to declare this:

def foo(input: bytes) -> str throwing ValueError:
   pass

Don't know if anybody suggested something like this feature so far at cpython.
It would help for auto-documentation.