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Auto-close Datasette instances from function-scoped fixtures too

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The plugin now tracks instances across the full test protocol (setup,
call, teardown) and closes all of them at the end — including ones
created inside function-scoped pytest fixtures. Session-, module-,
class- and package-scoped fixtures are still exempted by subtracting
any instances their setup adds from the tracking list.

This makes downstream projects like datasette-alerts work at low FD
limits without every fixture needing an explicit ds.close() call.

Refs #2692
See https://github.com/simonw/datasette/issues/2692#issuecomment-4265072230

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
This commit is contained in:
Simon Willison 2026-04-16 20:32:19 -07:00
commit df96e12737
1 changed files with 33 additions and 3 deletions
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36
datasette/_pytest_plugin.py
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@ -1,6 +1,9 @@
"""
Pytest plugin that automatically closes any Datasette instances constructed
inside a test body. Fixture-scoped instances survive.
during a pytest test — both in the test body and in function-scoped
fixtures. Instances constructed by session-, module-, class- or package-
scoped fixtures are left alone, because other tests in the session will
still want to use them.
Registered as a pytest11 entry point in pyproject.toml so that downstream
projects using Datasette get the same FD-safety net for their own tests.
@ -40,7 +43,7 @@ def pytest_addoption(parser):
"datasette_autoclose",
help=(
"Automatically close Datasette instances created inside test "
"bodies (default: true)."
"bodies and function-scoped fixtures (default: true)."
),
default="true",
)
@ -54,7 +57,8 @@ def _enabled(config) -> bool:
@pytest.hookimpl(hookwrapper=True)
def pytest_runtest_call(item):
def pytest_runtest_protocol(item, nextitem):
"""Track Datasette instances across setup, call and teardown; close at end."""
if not _enabled(item.config):
yield
return
@ -76,3 +80,29 @@ def pytest_runtest_call(item):
f"Error closing Datasette instance: {e!r}"
)
)
@pytest.hookimpl(hookwrapper=True)
def pytest_fixture_setup(fixturedef, request):
"""Exempt instances created by non-function-scoped fixtures.
Session-, module-, class- and package-scoped fixtures produce Datasette
instances that must survive beyond the current test — other tests in
the session will still use them. When such a fixture creates one or
more Datasette instances during its setup, we snapshot the tracking
list before the fixture runs and subtract off any instances that were
added during its setup, so they don't get closed at test teardown.
"""
refs = _active_instances.get()
if refs is None:
yield
return
before_ids = {id(ref) for ref in refs}
yield
if fixturedef.scope != "function":
new_refs = [ref for ref in refs if id(ref) not in before_ids]
for new_ref in new_refs:
try:
refs.remove(new_ref)
except ValueError:
pass