When generating Vala coverage, govr fails to find source files

[Cogitri]

Describe the bug
When generating coverage for Vala projects, gcovr fails to find source files, throwing the following error messages when running ninja -C build coverage-text:

ninja -C build/ coverage-text
[1/1] Generates text coverage report
lcov: LCOV version 20190809-346-g0d75ff8980
genhtml: LCOV version 20190809-346-g0d75ff8980
(WARNING) GCOV produced the following errors processing /home/rasmus/Projects/vala-test/build/test-lib/a915ebc@@lib.vala@sta/meson-generated_lib.c.gcda:
	Cannot open source file test-lib/a915ebc@@lib.vala@sta/lib.c
Cannot open source file ../test-lib/lib.vala
Cannot open source file lib.c

	Cannot open source file test-lib/a915ebc@@lib.vala@sta/lib.c
Cannot open source file ../test-lib/lib.vala
Cannot open source file lib.c

	Cannot open source file test-lib/a915ebc@@lib.vala@sta/lib.c
Cannot open source file ../test-lib/lib.vala

	Cannot open source file test-lib/a915ebc@@lib.vala@sta/lib.c
Cannot open source file ../test-lib/lib.vala
Cannot open source file lib.c

	Cannot open source file lib.c

	Cannot open source file test-lib/a915ebc@@lib.vala@sta/lib.c
Cannot open source file ../test-lib/lib.vala
Cannot open source file lib.c

	Cannot open source file test-lib/a915ebc@@lib.vala@sta/lib.c
Cannot open source file ../test-lib/lib.vala
Cannot open source file lib.c

	Cannot open source file test-lib/a915ebc@@lib.vala@sta/lib.c
Cannot open source file ../test-lib/lib.vala
Cannot open source file lib.c

	Could not open output file 'test-lib#a915ebc@@lib.vala@sta#lib.c.gcov'
Could not open output file '^#test-lib#lib.vala.gcov'
Could not open output file 'lib.c.gcov'

	Could not open output file 'test-lib#a915ebc@@lib.vala@sta#lib.c.gcov'
Could not open output file '^#test-lib#lib.vala.gcov'
Could not open output file 'lib.c.gcov'

	(gcovr could not infer a working directory that resolved it.)
(WARNING) GCOV produced the following errors processing /home/rasmus/Projects/vala-test/build/tests/59830eb@@test-exe@exe/meson-generated_test.c.gcda:
	Cannot open source file test.c
Cannot open source file ../tests/test.vala
Cannot open source file tests/59830eb@@test-exe@exe/test.c

	Cannot open source file test.c
Cannot open source file ../tests/test.vala
Cannot open source file tests/59830eb@@test-exe@exe/test.c

	Cannot open source file ../tests/test.vala
Cannot open source file tests/59830eb@@test-exe@exe/test.c

	Cannot open source file test.c
Cannot open source file ../tests/test.vala
Cannot open source file tests/59830eb@@test-exe@exe/test.c

	Cannot open source file test.c

	Cannot open source file test.c
Cannot open source file ../tests/test.vala
Cannot open source file tests/59830eb@@test-exe@exe/test.c

	Cannot open source file test.c
Cannot open source file ../tests/test.vala
Cannot open source file tests/59830eb@@test-exe@exe/test.c

	Cannot open source file test.c
Cannot open source file ../tests/test.vala
Cannot open source file tests/59830eb@@test-exe@exe/test.c

	Could not open output file 'test.c.gcov'
Could not open output file '^#tests#test.vala.gcov'
Could not open output file 'tests#59830eb@@test-exe@exe#test.c.gcov'

	Could not open output file 'test.c.gcov'
Could not open output file '^#tests#test.vala.gcov'
Could not open output file 'tests#59830eb@@test-exe@exe#test.c.gcov'

	(gcovr could not infer a working directory that resolved it.)

Text coverage report can be found at file:///home/rasmus/Projects/vala-test/build/meson-logs/coverage.txt

coverage.txt doesn't contain any info:

------------------------------------------------------------------------------
                           GCC Code Coverage Report
Directory: /home/rasmus/Projects/vala-test
------------------------------------------------------------------------------
File                                       Lines    Exec  Cover   Missing
------------------------------------------------------------------------------
------------------------------------------------------------------------------
TOTAL                                          0       0    --%
------------------------------------------------------------------------------

To Reproduce
See the repo https://github.com/Cogitri/meson-vala-coverage-bug-reproducer for a minimal reproducer.

Expected behavior
gcovr should be able to find source files and as such generate coverage data.

system parameters

• Is this a cross build or just a plain native build (for the same computer)? No
• what operating system (e.g. MacOS Catalina, Windows 10, CentOS 8.0, Ubuntu 18.04, etc.) Tested on Ubuntu 20.04 and Alpine Linux 3.12
• what Python version are you using e.g. 3.8.0: 3.9.3
• what meson --version: 0.54.3
• what ninja --version if it's a Ninja build: 1.9.0

[sergiotarxz]

This bug continues happening currently.