util-genai: record cancellation as a failure, not a success

[ordemri]

Description

GenAIInvocation.__exit__ called fail() only when the in-flight exception derived from
Exception, so asyncio.CancelledError took the stop() branch: a cancelled operation was exported
with StatusCode.UNSET, no error.type, and a duration metric with no error dimension —
indistinguishable from one that completed. This guards on BaseException instead, matching the guard
the stream wrappers in stream.py already use.

fail() already accepts a BaseException, so nothing else changed. __exit__ still returns None
— suppressing CancelledError would break asyncio cancellation for every caller — and two tests
cover that, one of them cancelling a real task mid-await.

Known gaps

• The wider guard also catches KeyboardInterrupt, SystemExit and GeneratorExit. GeneratorExit
  is not reachable from any shipped instrumentation today — no with <invocation>: block in this
  repository contains a yield — but it is covered by a test. Happy to narrow this; it is one line.
• This fixes the context-manager path only. Packages that finalize in their own except Exception:
  handler are worse off than unfixed, not equal: on cancellation neither branch runs and the span
  is never ended, so nothing is exported at all. Happy to follow up separately.

Type of change

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

How has this been tested?

New tests in util/opentelemetry-util-genai/tests/test_invocation_base_exception.py, written before
the fix and confirmed red against unmodified main: 6 failed, 342 passed — five with
AssertionError: <StatusCode.UNSET: 0> != <StatusCode.ERROR: 2>, one with KeyError: 'error.type'.
The file's other tests passed before and after, so it discriminates rather than failing wholesale.

• tox -e py310-test-util-genai — 348 passed
• tox -e py314-test-util-genai — 348 passed
• tox -e py310-test-instrumentation-genai-agno-oldest — 20 passed
• tox -e py310-test-instrumentation-genai-agno-latest — 20 passed
• tox -e py314-test-instrumentation-genai-agno-latest — 20 passed
• google-genai and smolagents oldest / latest — passed
• Conformance environments not verified: they skip locally because the weaver binary is not
  installed, so no assertion ran. Relying on CI for those.

Checklist

• Followed the style guidelines of this project
• Changelog updated
• Unit tests added
• Documentation updated — not applicable

[Copilot]

Pull request overview

This PR fixes util-genai’s invocation context-manager finalization so cancellations and other BaseException cases are recorded as failures (via fail()), preventing cancelled operations from being exported indistinguishably from successful ones.

Changes:

• Update GenAIInvocation.__exit__ to treat any non-None exc_value: BaseException as failure, aligning behavior with existing stream wrapper guards.
• Add new unit tests covering CancelledError, KeyboardInterrupt, SystemExit, GeneratorExit, and ensuring cancellation is not suppressed.
• Add a towncrier changelog fragment describing the bug fix.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
util/opentelemetry-util-genai/src/opentelemetry/util/genai/_invocation.py	Treat BaseException in __exit__ as failure to correctly mark cancellation/interruption as errors.
util/opentelemetry-util-genai/tests/test_invocation_base_exception.py	New tests verifying __exit__ failure semantics for BaseException and that cancellation still propagates.
util/opentelemetry-util-genai/.changelog/PRNUMBER.fixed	Changelog fragment documenting the cancellation-as-failure fix.

Suppressed comments (2)

util/opentelemetry-util-genai/tests/test_invocation_base_exception.py:162

• test_cancellation_of_a_task_still_cancels_it can hang for up to 60s (or indefinitely on started.wait()) if cancellation doesn’t propagate as expected. Adding a short asyncio.wait_for timeout makes the test fail fast instead of stalling the suite.

            task = asyncio.ensure_future(work())
            await started.wait()
            task.cancel()
            with pytest.raises(asyncio.CancelledError):
                await task

util/opentelemetry-util-genai/tests/test_invocation_base_exception.py:119

• This assertion hardcodes the CancelledError module path (asyncio.exceptions...), which can change between Python versions. Compute the expected error.type using fq_exception_type to avoid version-specific failures.

        self.assertEqual(
            span.attributes["error.type"], "asyncio.exceptions.CancelledError"
        )

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Merged · refreshed 2026-09-04 22:19 UTC

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[lmolkova]

Thank you!