feat: add support for configuring metric scope labels

[herin049]

Description

Adds support for configuring scope labels on the Prometheus exporter in accordance with the Prometheus spec The default behavior is to include scope labels in exported metrics.

Furthermore this PR includes changes to refactor the conversion of OTel metrics to Prometheus metrics.

Fixes #5112

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

uv run tox -e py314-test-opentelemetry-exporter-prometheus

Does This PR Require a Contrib Repo Change?

• Yes. - Link to PR:
• No.

Checklist:

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated

[MikeGoldsmith]

This looks like it's on the right path. A few things to note:

1. _SCOPE_ATTR_CONFLICT_NAMES is defined but never used — we should either use it to explicitly filter conflicting scope attributes or remove it.

2. PR description looks copy-pasted from #5122 — says "Resource metrics as Metric attributes" but this is about scope info.

3. Merge conflict concern — this, #5122, #5118, and #5117 all modify PrometheusMetricReader and _translate_to_prometheus. This is going to conflict with them, we need to coordinate what should be done in order or we'll be bumping into each other with rebases.

4. nit: the nesting depth in _translate_to_prometheus is getting deep — might be worth extracting the per-metric logic into a helper in a follow-up.

[herin049]

This looks like it's on the right path. A few things to note:

1. _SCOPE_ATTR_CONFLICT_NAMES is defined but never used — we should either use it to explicitly filter conflicting scope attributes or remove it.
2. PR description looks copy-pasted from opentelemetry-exporter-prometheus: add support to configure Resource attributes as metric labels #5122 — says "Resource metrics as Metric attributes" but this is about scope info.
3. Merge conflict concern — this, opentelemetry-exporter-prometheus: add support to configure Resource attributes as metric labels #5122, feat: add metric name translation strategy support for the Prometheus exporter #5118, and feat(exporter/prometheus): add default_aggregation parameter to PrometheusMetricReader #5117 all modify PrometheusMetricReader and _translate_to_prometheus. This is going to conflict with them, we need to coordinate what should be done in order or we'll be bumping into each other with rebases.
4. nit: the nesting depth in _translate_to_prometheus is getting deep — might be worth extracting the per-metric logic into a helper in a follow-up.

Sorry, got a little sloppy with this PR. I originally used _SCOPE_ATTR_CONFLICT_NAMES, but refactored the code so that it isn't needed anymore. The update order shouldn't matter much, I can address the merge conflicts as they come in. Updated the PR description, will clean up the PR.

[herin049]

@MikeGoldsmith I ended up doing a pretty major refactor of the exporter logic based on your suggestion, so we will likely want to merge this PR first.

[MikeGoldsmith]

Looks good, thanks @herin049. Need to update PR title and description.

[ArthurSens]

Hey, just a heads-up from the Prometheus SIG: please hold off on the merge here. There's on going discussion happening on the PR that stabilizes this part of the spec open-telemetry/opentelemetry-specification#5056

[MikeGoldsmith]

Moving to draft until the SIG confirms this is the correct path.

[github-actions]

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[Copilot]

Pull request overview

Adds Prometheus exporter support for including (and optionally disabling) instrumentation scope labels on exported metrics, aligning the exporter with the spec’s Scope Info guidance, and refactors the OTel→Prometheus translation pipeline to be more modular.

Changes:

• Add scope label emission (otel_scope_name, otel_scope_version, otel_scope_schema_url, and otel_scope_* scope attributes) with a toggle (scope_info_enabled).
• Refactor metric translation into helper functions for family creation/population and data-point collection.
• Add/adjust unit tests and update Prometheus exporter documentation and changelog entry.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

File	Description
exporter/opentelemetry-exporter-prometheus/tests/test_prometheus_exporter.py	Adds tests for default/disabled scope labels and updates existing tests to account for new default behavior.
exporter/opentelemetry-exporter-prometheus/src/opentelemetry/exporter/prometheus/init.py	Implements scope label handling and refactors translation logic into smaller helpers.
docs/exporter/prometheus/prometheus.rst	Documents scope label behavior and configuration.
.changelog/5123.added	Notes the new Prometheus exporter feature.

Comments suppressed due to low confidence (1)

exporter/opentelemetry-exporter-prometheus/src/opentelemetry/exporter/prometheus/init.py:288

• This PR adds scope_info_enabled on PrometheusMetricReader, but the SDK's config-based Prometheus factory still logs that without_scope_info is unsupported and ignores it (opentelemetry-sdk/src/opentelemetry/sdk/_configuration/_meter_provider.py, around _create_prometheus_metric_reader). That means "configuring scope labels" won't work for users relying on SDK configuration / opentelemetry-instrument unless that path is updated (or an alias parameter is supported).

    def __init__(
        self,
        disable_target_info: bool = False,
        prefix: str = "",
        scope_info_enabled: bool = True,
        *,
        registry: CollectorRegistry = REGISTRY,
    ) -> None:
        super().__init__(
            preferred_temporality={
                Counter: AggregationTemporality.CUMULATIVE,
                UpDownCounter: AggregationTemporality.CUMULATIVE,
                HistogramInstrument: AggregationTemporality.CUMULATIVE,
                ObservableCounter: AggregationTemporality.CUMULATIVE,
                ObservableUpDownCounter: AggregationTemporality.CUMULATIVE,
                ObservableGauge: AggregationTemporality.CUMULATIVE,
            },
            otel_component_type=OtelComponentTypeValues.PROMETHEUS_HTTP_TEXT_METRIC_EXPORTER,
        )
        self._collector = _CustomCollector(
            disable_target_info=disable_target_info,
            prefix=prefix,
            scope_info_enabled=scope_info_enabled,
        )
        self._registry = registry
        self._registry.register(self._collector)
        self._collector._callback = self.collect
        self._prefix = prefix

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