Using `--include` to also report on un-executed files or filter out files from `--source`

[BurnzZ]

Is your feature request related to a problem? Please describe.

Using --include to also report on un-executed files. Here's a use case:

foo.py:

def foo():
    return "bar"

test.py:

from foo import foo

def test_foo():
    assert foo() == "bar"

if __name__ == "__main__":
    test_foo()

untested.py:

def not_tested_nor_imported():
    return "untested"

Running coverage run test.py && coverage report results in:

Name      Stmts   Miss  Cover
-----------------------------
foo.py        2      0   100%
test.py       5      0   100%
-----------------------------
TOTAL         7      0   100%

Running coverage run --source=. test.py && coverage report results in:

Name          Stmts   Miss  Cover
---------------------------------
foo.py            2      0   100%
test.py           5      0   100%
untested.py       2      2     0%
---------------------------------
TOTAL             9      2    78%

So far so good! ✅ We can force the untested files to be in the report as per the docs:

Specifying the source option also enables coverage.py to report on un-executed files, since it can search the source tree for files that haven’t been measured at all.

However, using --include to force specific files coverage run --include="foo.py,untested.py" test.py && coverage report still omits the untested.py file.

Name     Stmts   Miss  Cover
----------------------------
foo.py       2      0   100%
----------------------------
TOTAL        2      0   100%

Describe the solution you'd like

It'd be great if we can use --include to also get coverage reports on specific files.

Describe alternatives you've considered

Perhaps we can use --include to filter out the files in --source, as the current behavior currently ignores --include:

--include is ignored because --source is set (include-ignored)

One workaround is to use --omit to exclude some files from --source which can give you files for --include. However, certain cases makes this hard (e.g. large code base being tested but you only want to --include a couple of files).