fix(sdk): raise error when named view specifies no instrument name (#2815)

[dlowzzxx]

Description

According to the OpenTelemetry Metrics SDK Specification:

In order to avoid conflicts, views which specify a name SHOULD have an instrument selector that selects at most one instrument. For the registration mechanism described above, where selection is provided via configuration, the SDK SHOULD NOT allow Views with a specified name to be declared with instrument selectors that may select more than one instrument (e.g. wild card instrument name) in the same Meter.

Previously, View validation checked for wildcard characters in instrument_name only when instrument_name is not None. However, omitting instrument_name while specifying name (e.g. View(name="custom_name", instrument_type=Counter)) implicitly selects all instruments matching that type or meter criteria, which may select multiple instruments in the same Meter.

This PR adds a check in View.__init__ that raises an Exception when name is specified but instrument_name is omitted (None), ensuring consistency with the specification and wildcard validation.

Fixes #2815

Type of change

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

How Has This Been Tested?

• Added unit tests in opentelemetry-sdk/tests/metrics/test_view.py:
  • test_view_name_wildcard: asserts wildcard characters (*, ?) in named views continue to raise Exception.
  • test_view_name_without_instrument_name: asserts defining a named View without instrument_name (e.g., with instrument_type, meter_name, instrument_unit, meter_version, meter_schema_url) raises Exception.
  • test_view_name_with_concrete_instrument_name: asserts that named views with concrete instrument_name work as expected.
• Verified test suite:
  • pytest opentelemetry-sdk/tests/metrics/test_view.py opentelemetry-sdk/tests/metrics/test_view_instrument_match.py opentelemetry-sdk/tests/metrics/test_metric_reader_storage.py (47/47 passing).
  • ruff check and ruff format --check passed cleanly.

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

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Pull request dashboard status

Waiting on maintainers · refreshed 2026-09-29 22:27 UTC

Resolve merge conflicts, then merge when ready.

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[Copilot]

Copilot review overview

🟡 Changes recommended

Bracket wildcard patterns can still allow a named view to match multiple instruments.

Get a fresh assessment by requesting another Copilot review.

Review effort: Balanced
Findings: 1

Open (1)

• Reject bracket wildcards in instrument name matching · New

What changed in this PR

Updates Metrics SDK View validation to prevent named views from broadly selecting instruments.

Changes:

• Requires named views to specify instrument_name.
• Adds validation tests and documentation.
• Adds a changelog entry.

File	Description
opentelemetry-sdk/​tests/​metrics/​test_view.py	Tests named-view validation.
opentelemetry-sdk/​src/​opentelemetry/​sdk/​metrics/​_internal/​view.py	Enforces instrument-name requirements.
.changelog/​5631.fixed	Documents the fix.

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