DEBUG-3176 DI: report an error when instrumenting a loaded file that is not in registry

[p-datadog]

What does this PR do?

Ruby stores the list of loaded files in $LOADED_FEATURES. Use this list to detect line probes that attempt to instrument files that have been loaded prior to code tracking being active, and report error to the user when instrumenting those files (since they won’t ever be instrumented in production).

Motivation:

Better diagnostics for DI.

Change log entry

Report instrumentation error in dynamic instrumentation when attempting to instrument line probes and the target file is loaded but not in code tracker registry.

Additional Notes:

The check can be expensive because it performs path suffix matching for potentially thousands of file paths corresponding to the loaded files.

How to test the change?

Unit tests are included

[github-actions]

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^{Visited at: 2024-12-12 17:06:20 UTC}

[pr-commenter]

Benchmarks

Benchmark execution time: 2024-12-09 15:34:41

Comparing candidate commit 1534132 in PR branch di-loaded-features with baseline commit 38fee9b in branch master.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 31 metrics, 2 unstable metrics.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 87.50000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 97.77%. Comparing base (38fee9b) to head (1534132).

Files with missing lines	Patch %	Lines
lib/datadog/di/instrumenter.rb	77.77%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4208      +/-   ##
==========================================
- Coverage   97.77%   97.77%   -0.01%     
==========================================
  Files        1357     1357              
  Lines       81973    81989      +16     
  Branches     4168     4173       +5     
==========================================
+ Hits        80149    80162      +13     
- Misses       1824     1827       +3     

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[p-datadog]

Note that this PR only applies to files loaded via require, not load. Files loaded via load are not added to $LOADED_FEATURES and thus cannot be identified by the check added in this PR.