Proposal: fixture-owned notes via request.add_note (refine #1376)

[RonnyPfannschmidt]

What's the problem this feature will solve?

Refines / supersedes #1376.

Fixtures often know useful context (DB paths, hosts, ports, etc.). Printing it loses that context in captured output. There is no first-class way for a fixture to attach notes that:

1. belong to the fixture instance (including higher scopes),
2. are available to every dependent test that uses that instance,
3. show cleanly on failure without pass-path noise,
4. are available to report consumers (TestReport, reportlog, etc.).

Item-local escapes (print, add_report_section, user_properties) do not model scoped fixture ownership.

Describe the solution you'd like

API

@pytest.fixture(scope="session")
def db(request):
    path = mk_db()
    request.add_note(f"db path: {path}")
    request.add_note({"path": str(path), "engine": "sqlite"})
    yield path

def add_note(self, note: str | dict[str, str]) -> None: ...

• Named like BaseException.add_note.
• Calls append; str or dict[str, str] in v1.
• Notes are owned by the fixture instance / its scope, not by the requesting item.

Behavior

• Notes are projected into test reports for dependents of that fixture instance (including passes, for tooling).
• Terminal shows them only on failure.
• Higher-scope notes appear on every dependent test report by design.
• Later: keep room for richer note payloads; not required in v1.

Out of scope

• First-class fixture report nodes / reworking setup-teardown attribution.
• Skipping dependents when a scoped fixture fails.
• Showing notes on passing tests in the terminal.
• Rich renderable public API in v1.

Alternative Solutions

• print / logging — unstructured, lost in capture.
• add_report_section / user_properties — item-local; wrong owner for scoped fixtures.
• Original allow fixtures to provide extra info when a test fails #1376 add_info_on_failure only — too narrow for fixture-owned notes shared across dependents.

Additional context

Related: #1376. Intentional split: Holger’s failure-context need, plus fixture-owned notes visible to all dependents; larger fixture-report-node work stays separate.