[dashpole]

Part of #1841

Changes

Update PrometheusExporterUtils::TranslateToPrometheus to conform to the Metric Metadata section of the OpenTelemetry Prometheus and OpenMetrics Compatibility Specification:

• Merge metrics across scopes (or unit/suffix-stripped instruments) that translate to the same Prometheus metric name and MetricType into a single MetricFamily so duplicate # HELP and # TYPE headers are not emitted. When descriptions differ, retain the first HELP description and log a warning.
• Drop metrics that translate to an existing Prometheus metric name with a conflicting MetricType and log a warning.

(Pre-existing bug fixes have been split into #4738.)

For full trivial changes below, please confirm you have:

• Formatted the code using clang-format
• Updated CHANGELOG.md if applicable

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🟡 Changes recommended

Collision handling uses the generated Info family’s internal name and type rather than its Prometheus text representation, causing incorrect drops and missed collisions.

1 open issue

• Resolve target_info collisions using exposed family name and type · New

What changed in this PR

This PR advances #1841 by handling metric-family collisions in the Prometheus exporter, reducing duplicate metadata across instrumentation scopes.

Changes:

• Merge families with matching translated names and types, keeping the first description and warning on differences.
• Drop conflicting metric types and skip empty point collections.
• Add collision regression coverage and a changelog entry.

File	Description
exporters/​prometheus/​test/​exporter_utils_test.cc	Tests cross-scope merging, description retention, and type-conflict dropping.
exporters/​prometheus/​src/​exporter_utils.cc	Adds family indexing, collision handling, and an empty-point guard.
CHANGELOG.md	Documents the exporter behavior change under Unreleased.

_{Review effort: Balanced}

[codecov]

Codecov Report

❌ Patch coverage is 96.42857% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 86.70%. Comparing base (e854d29) to head (d763e4d).

Files with missing lines	Patch %	Lines
exporters/prometheus/src/exporter_utils.cc	96.43%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4736      +/-   ##
==========================================
+ Coverage   86.69%   86.70%   +0.02%     
==========================================
  Files         527      527              
  Lines       20902    20916      +14     
==========================================
+ Hits        18119    18134      +15     
+ Misses       2783     2782       -1     

Files with missing lines	Coverage Δ
exporters/prometheus/src/exporter_utils.cc	89.97% <96.43%> (+0.77%)	⬆️

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