[CONFIGURATION] File configuration - composable samplers

[DCchoudhury15]

Fixes #3914

Changes

This PR implements the necessary infrastructure and test coverage to fully support composable samplers. Specifically, the changes include:

• Parser Logic: Implemented the YAML parsing logic to properly extract composable sampler configurations.
• SDK Builder: Added SDK builder visitor instantiation to correctly wire the new sampler variants.
• Test Safety: Replaced dangerous casts with the safe Visitor pattern in the testing suite.
• Test Coverage: Expanded unit test coverage to ensure all composable sampler variants are accurately parsed and instantiated.

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

[codecov]

Codecov Report

❌ Patch coverage is 89.33333% with 16 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.83%. Comparing base (c49458d) to head (8958736).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
sdk/src/configuration/configuration_parser.cc	87.20%	16 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3966      +/-   ##
==========================================
+ Coverage   81.75%   81.83%   +0.09%     
==========================================
  Files         374      389      +15     
  Lines       16083    16234     +151     
==========================================
+ Hits        13147    13284     +137     
- Misses       2936     2950      +14     

Files with missing lines	Coverage Δ
...tion/composable_always_off_sampler_configuration.h	100.00% <100.00%> (ø)
...ation/composable_always_on_sampler_configuration.h	100.00% <100.00%> (ø)
...omposable_parent_threshold_sampler_configuration.h	100.00% <100.00%> (ø)
...ion/composable_probability_sampler_configuration.h	100.00% <100.00%> (ø)
...tion/composable_rule_based_sampler_configuration.h	100.00% <100.00%> (ø)
...ed_sampler_rule_attribute_patterns_configuration.h	100.00% <100.00%> (ø)
...ased_sampler_rule_attribute_values_configuration.h	100.00% <100.00%> (ø)
...composable_rule_based_sampler_rule_configuration.h	100.00% <100.00%> (ø)
...k/configuration/composable_sampler_configuration.h	100.00% <100.00%> (ø)
.../sdk/configuration/sampler_configuration_visitor.h	100.00% <ø> (ø)
... and 6 more

... and 2 files with indirect coverage changes

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[marcalff]

@DCchoudhury15

Thanks for the PR.

Please check the CI logs for failures, and adjust the code accordingly.

In the mean time, I will start the code review and provide feedback.

Thanks for your contribution.

Examples of failures below

---

Include what you use:

[ 57%] Building CXX object sdk/src/configuration/CMakeFiles/opentelemetry_configuration.dir/yaml_configuration_parser.cc.o
Warning: include-what-you-use reported diagnostics:

/home/runner/work/opentelemetry-cpp/opentelemetry-cpp/sdk/src/configuration/configuration_parser.cc should add these lines:
#include "opentelemetry/sdk/configuration/composable_always_off_sampler_configuration.h"
#include "opentelemetry/sdk/configuration/composable_always_on_sampler_configuration.h"
#include "opentelemetry/sdk/configuration/composable_parent_threshold_sampler_configuration.h"
#include "opentelemetry/sdk/configuration/composable_probability_sampler_configuration.h"
#include "opentelemetry/sdk/configuration/composable_rule_based_sampler_configuration.h"
#include "opentelemetry/sdk/configuration/composable_sampler_configuration.h"

---

Build in maintainer mode

[ 53%] Building CXX object sdk/src/configuration/CMakeFiles/opentelemetry_configuration.dir/configuration_parser.cc.o
In file included from /home/runner/work/opentelemetry-cpp/opentelemetry-cpp/sdk/src/configuration/configuration_parser.cc:29:
In file included from /home/runner/work/opentelemetry-cpp/opentelemetry-cpp/sdk/include/opentelemetry/sdk/configuration/configuration_parser.h:20:
/home/runner/work/opentelemetry-cpp/opentelemetry-cpp/sdk/include/opentelemetry/sdk/configuration/composable_always_off_sampler_configuration.h:26:28: error: no newline at end of file [-Werror,-Wnewline-eof]
   26 | OPENTELEMETRY_END_NAMESPACE
      |                            ^

---

Clang-tidy

Download the clang-tidy report from ci, and inspect failures related to new code.


opentelemetry-cpp/sdk/include/opentelemetry/sdk/configuration/composable_always_off_sampler_configuration.h (1 warnings)Line Check Message15 cppcoreguidelines-special-member-functions class ‘ComposableAlwaysOffSamplerConfiguration’ defines a default destructor but
does not define a copy constructor, a copy assignment operator, a move constructor
or a move assignment operator 

[DCchoudhury15]

Hi @marcalff, addressed all the CI failures:

• Added direct includes in configuration_parser.cc (IWYU)
• Fixed missing newlines at end of the new headers (clang-tidy)
• Dropped the explicit destructors since the base class already handles it
  Also did some changes in the test visitor for a SamplerType enum while I was at it.
  Thanks for the patience!

[marcalff]

Thanks for the PR.

Focusing on the yaml part for now: all the yaml nodes and properties should be parsed, and represented in memory in C++ classes.

This includes rules with attribute_values, attribute_patterns and span_kinds.

[DCchoudhury15]

I have applied the changes given on the pr review , will resolve all the ci errors and commit again asap .

[marcalff]

LGTM, nice work.

In this pass, changes are just cosmetic for style.

Will approve and merge once fixed.

[marcalff]

LGTM, nice work.