fix(metrics): guard _advisory access in ExplicitBucketHistogramAggregation for non-Histogram instruments

[giorgiovilardo]

Description

ExplicitBucketHistogramAggregation._create_aggregation() unconditionally accesses instrument._advisory.explicit_bucket_boundaries when no explicit boundaries are provided. The _advisory attribute only exists on Histogram instruments — when this aggregation is applied to other instrument types (e.g. Counter) via preferred_aggregation, it raises AttributeError.

This became reachable in practice after TracerMetrics (added in 1.40.0) began registering Counter and UpDownCounter instruments through the global MeterProvider.

The fix uses a safe getattr guard, falling back to None boundaries when _advisory is absent.

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

• test_explicit_bucket_histogram_on_instrument_without_boundaries — applies ExplicitBucketHistogramAggregation() (no boundaries) to a _Counter instrument and asserts it produces a valid _ExplicitBucketHistogramAggregation instead of crashing

Does This PR Require a Contrib Repo Change?

• No.

Checklist:

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

Red/green tests:

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: giorgiovilardo / name: Giorgio Vilardo (5e58552, c29e93e)
• ✅ login: xrmx / name: Riccardo Magliocchetti (8e3ff20)

[xrmx]

Thanks for investigating this!