Assume if TYPE_CHECKING: ... else: ... block is covered

[retnikt]

if typing.TYPE_CHECKING blocks are never run but are still counted as needing test coverage.
( https://docs.python.org/3.7/library/typing.html#typing.TYPE_CHECKING )

Example

from typing import TYPE_CHECKING
if TYPE_CHECKING:
    # coverage.py thinks this is not covered because TYPE_CHECKING is True at runtime
    ...
else:
    ....

You have to add # pragma: no_cover to the if block here because coverage.py assumes TYPE_CHECKING to be False, and therefore assumes one of the blocks does not have a test case. It would be good if you didn't have to, and blocks requiring TYPE_CHECKING to be True are assumed to not need test cases.

[nedbat]

You can solve this yourself today by adding this to your .coveragerc file:

[report]
exclude_lines = 
    pragma: no cover
    if TYPE_CHECKING:

More details about this setting are here: Advanced exclusion.

Since this is something that is configurable by the user, I would rather not change coverage.py to deal with it.

[cjw296]

@nedbat - when would you expect code inside if TYPE_CHECKING blocks to be executed while code coverage measurement is in effect? How would you feel about making this part of the default exclude_lines?

[nedbat]

A few years later, I think you are right that it should be part of the default. If the user wants to measure those lines, they can.

[ikonst]

Can we also add ... to the defaults while we're at it?

[cjw296]

@ikonst - I'm not 100% sure that's a good idea, but also as I've painfully discovered, you really mean \.\.\..

[ikonst]

Yeah, obviously in its escaped form. I think the sharp change in coverage would tell you :)

[cjw296]

It can be quite the footgun when your projects are starting from 100% line coverage...

[Kludex]

A few years later, I think you are right that it should be part of the default. If the user wants to measure those lines, they can.

@nedbat Is the else from a if not TYPE_CHECKING: supposed to be supported as well? If yes, any tips where I can implement this part?

[ssbarnea]

While coveragepy itself seems to recognized the excluded lines as covered, it seems that uploading the reports to codecov.io does show them as not covered in their reporting. If someone spotted a workaround for that, please let me know.

[ikonst]

I think "excluded" is its own status in coveragepy, are you sure it's "covered" and not "excluded"? Or are you just concerned about coverage %?

[benjaoming]

Am I correct that solving this happens in these lines:

coveragepy/coverage/config.py

Lines 152 to 155 in fcdce1d

	# The default line exclusion regexes.
	DEFAULT_EXCLUDE = [
	r"#\s*(pragma|PRAGMA)[:\s]?\s*(no|NO)\s*(cover|COVER)",
	]

...+ adding test case(s)?

[nedbat]

Yes, that is where the default exclusions are defined.