[BUILD] Support pkg-config

[dbolduc]

Fixes #1850

Generates and installs pkgconfig (*.pc) files for the following targets:

• opentelemetry_api
• opentelemetry_logs
• opentelemetry_metrics
• opentelemetry_resources
• opentelemetry_trace
• opentelemetry_version

The API is necessary, because we need to capture cflags, such as -DWITH_ABSEIL. I did not think installing an opentelemetry_sdk.pc was necessary or helpful.

Motivation: googleapis/google-cloud-cpp#10795

Testing

I added a test to validate the installed package configs. This does not guarantee that their contents are 100% correct.

I am new to using the CI. I am yolo'ing the changes to .github/workflows/ci.yml. I ran the steps locally, though, and they were successful:

ci/run_docker.sh

# Then inside docker...
ci/setup_cmake.sh
ci/setup_ci_environment.sh
ci/install_abseil.sh
ci/do_ci.sh cmake.install.test
ci/verify_packages.sh

My test installs opentelemetry-cpp built -DWITH_ABSEIL. The dimensions we care about are: [with/without abseil, with/without gsl] (as far as the install logic for opentelemetry_api goes). But I did not want to write all these tests, so I just checked the abseil case.

Testing while developing

I did some more rigorous testing while developing. The changes are in this commit.

Basically it has an executable that uses OTel types. This executable is built using a Makefile, through the use of pkg-config. With it, I was able to confirm that the installed libraries link, the include directories work, the compile definitions work, etc.

I tested this with/without abseil for all of the added targets listed above.

[codecov]

Codecov Report

Merging #2269 (ce1b630) into main (11d5d9e) will increase coverage by 0.06%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2269      +/-   ##
==========================================
+ Coverage   87.47%   87.52%   +0.06%     
==========================================
  Files         199      199              
  Lines        5981     5981              
==========================================
+ Hits         5231     5234       +3     
+ Misses        750      747       -3     

see 1 file with indirect coverage changes

[dbolduc]

Sorry about iterating in the CI. It looks like the "Bazel tsan config" build is failing across the board, so I think this PR is ready for review.

[owent]

Can we replace the add_library function in otel-cpp with a new function which can call add_library and opentelemetry_add_pkgconfig.And then it could automatically add all cmake targets and ensure that the package name in pkgconfig matches the cmake package name?

[dbolduc]

Can we replace the add_library function in otlp-cpp with a new function which can call add_library and opentelemetry_add_pkgconfig.And then it could automatically add all cmake targets and ensure that the package name in pkgconfig matches the cmake package name?

opentelemetry_add_pkgconfig inspects properties of the library target:

opentelemetry-cpp/cmake/pkgconfig.cmake

Line 35 in b275af1

get_target_property(target_type ${target} TYPE)

... so I think we are already ensuring that the package name in pkgconfig matches the cmake package name.

This also means that we can only call opentelemetry_add_pkgconfig after all of the target_include_directories(target, ...) and target_compile_definitions(target, ...) have been set. I think this means we can not combine the add_library and opentelemetry_add_pkgconfig functions.

otlp-cpp

Sorry if I am misunderstanding your question. I am not so sure what this is. I did not touch any of the OTLP components. We can always address them in a follow up PR.

[owent]

This also means that we can only call opentelemetry_add_pkgconfig after all of the target_include_directories(target, ...) and target_compile_definitions(target, ...) have been set. I think this means we can not combine the add_library and opentelemetry_add_pkgconfig functions.

Thanks, I think it's fine.

Sorry if I am misunderstanding your question. I am not so sure what this is. I did not touch any of the OTLP components. We can always address them in a follow up PR.
Sorry for my mistake. I mean otel-cpp, not OTLP.

[owent]

LGTM and thanks.

[dbolduc]

Any chance this feature makes it into the v1.11.0 release?

[lalitb]

Nicely done. Thanks for contributing.

@ThomsonTan - Do you think it can be included in the v1.11.0?

[ThomsonTan]

Nicely done. Thanks for contributing.

@ThomsonTan - Do you think it can be included in the v1.11.0?

This is missed in the v1.1.0 release. As this is a new feature, I think it will be good to stay in main for a release cycle.

[dbolduc]

As this is a new feature, I think it will be good to stay in main for a release cycle.

Ack. Thanks for merging.