Resolve dependencies in opentelemetry-cpp-config.cmake

[tobim]

Before this change, consumers of the exported CMake targets had to know which dependencies are needed to get the transitive target dependencies like absl::*, gRPC::grpc++, or protobuf::libprotobuf.

Fixes # (issue)

Changes

Please provide a brief description of the changes here.

For significant contributions please make sure you have completed the following items:

• [ ] CHANGELOG.md updated for non-trivial changes
• [ ] Unit tests have been added
• [ ] Changes in public API reviewed

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Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 87.91%. Comparing base (497eaf4) to head (7225046). Report is 150 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3094      +/-   ##
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+ Coverage   87.12%   87.91%   +0.79%     
==========================================
  Files         200      195       -5     
  Lines        6109     6133      +24     
==========================================
+ Hits         5322     5391      +69     
+ Misses        787      742      -45     

see 98 files with indirect coverage changes

[owent]

find_package will produce warning when it's called recursively. Shoud we just add warnings to let users call find_package for dependencies before otel-cpp?

[tobim]

find_package will produce warning when it's called recursively.

What warnings? Calling find_package or find_dependency in config files is standard practice.

[tobim]

I now realize that my earlier response might has come across as rude, which I did not intend. Please take a look at the docs for find_dependency here. Quoting:

It is designed to be used in a Package Configuration File (<PackageName>Config.cmake).

May I humbly request that you take another look?

[owent]

find_package will produce warning when it's called recursively.

What warnings? Calling find_package or find_dependency in config files is standard practice.

Sorry, calling find_package recursively with FindXXX.cmake will produce warnings, but won't with CONFIG package. Could you please also add find_dependency for OpenTracing, prometheus-cpp, CURL and ZLIB ?

[tobim]

Thanks for the heads-up! I added the rest. Afaics CURL and ZLIB are only necessary when opentelemetry_http_client_curl is built as a static library, so I guarded that with NOT BUILD_SHARED_LIBS.