Fix parsing of gcov metadata

[Spacetown]

Gcc-11 has metadata lines without values in the gcov file (see #596). This PR add support for this lines and uses as value None.

Closes #596.

[codecov]

Codecov Report

Merging #601 (543c495) into master (79a45db) will decrease coverage by 0.05%.
The diff coverage is 75.00%.

@@            Coverage Diff             @@
##           master     #601      +/-   ##
==========================================
- Coverage   95.19%   95.14%   -0.06%     
==========================================
  Files          23       23              
  Lines        3350     3355       +5     
  Branches      614      616       +2     
==========================================
+ Hits         3189     3192       +3     
- Misses         89       90       +1     
- Partials       72       73       +1     

Flag	Coverage Δ
ubuntu-18.04	93.94% <75.00%> (-0.06%)	⬇️
windows-2019	94.79% <75.00%> (-0.06%)	⬇️

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Impacted Files	Coverage Δ
gcovr/gcov.py	75.59% <33.33%> (-0.51%)	⬇️
gcovr/gcov_parser.py	100.00% <100.00%> (ø)

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[latk]

simple and elegant :)

Using a None value does kind of violate the type annotations around that code, but for now this won't break anything and that can be fixed in the next refactoring push.

(If you want to fix this, note that now the metadata values are not str but Optional[str]. This also means the metadata["Source"] access in process_gcov_data() could be None, as far as the type system is concerned. The most elegant approach to solve this would be to move the “Source must exist” check from the metadata-parser into process-gcov-data, to something like source = metadata.get("Source"); if source is None: raise RuntimeError(...))

[Spacetown]

@latk I've moved the strip to the parsing of the metadata. How can I force a leading whitespace in the doctest if the editor removes them.

[latk]

How can I force a leading whitespace in the doctest if the editor removes them.

I don't entirely understand. Could you show an example of what you want to do?

[Spacetown]

I wan't to add leading whitespaces to the following doctest:

    >>> parse_metadata('''
    ...   -: 0:Foo:bar
    ...   -: 0:Key:123
    ... '''.splitlines())

The whitepaces shouldn't be removed by the editor on save.

One solution is to write a single line string with \n.