Add pytest.register_fixture#14568
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The override chain for a fixture name was determined by the semi-incidental order in which fixturedefs were registered, with an ad-hoc tweak that pushed fixturedefs with no location to the front of the list (the last one is used first). Order the fixturedef list by partial order based on visibility instead: a fixturedef whose visibility is more specific (a descendant in the collection tree) sorts after a more general (ancestor) one, so it takes precedence in the override chain. Fixturedefs with non-comparable visibility keep registration order (last registered wins). The idea is that a fixture that defined closer to the item should take precedence. This generalizes the previous "no location" handling and makes precedence robust for programmatically registered fixtures. The code is complicated by the need to support FixtureDefs with legacy string nodeids rather than Nodes visibility, but these are deprecated and will removed in pytest 10, then we can remove the compat code. Also, comparing Nodes by visibility is not a super fast operation, since we need to look at the actual tree. However, I think overrides are not widely used and when they do, the chains are not very long, so hopefully that's fine. But it can be optimized using some tricks if necessary. Fix #14513
has_location was used to determine the fixture override order, pushing fixturedefs with no location to the front of the override chain. Now that the override order is determined by the fixtures' visibility in the collection tree, the attribute is no longer needed. Turn it into a property that emits a PytestRemovedIn10Warning, backed by the private _has_location attribute, and document the deprecation.
…ility instead of None Let's get rid of the `None` global visibility. Use `Session` which is functionality equivalent instead. - Allows us to remove an annoying special case from the fixture core. - Allows a cleaner public `register_fixture` interface (upcoming). There was previously a distinction between "has location" (e.g. conftest plugins) and "no location" (e.g. external plugins), but it's no longer needed after recent changes. Since initial conftest plugins are always registered after core & external plugins, the override chain order is maintained.
The nodeid-visibility/baseid deprecation previously allowed None (global) visibility. But this visibility is no longer needed, should use Session visibility instead. So let's include it in the deprecation as well, this way we can have a clean break in pytest 10.
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This PR is stacked on:
get_scope_packagewhen possible #14565FixtureDef.has_locationandNoneglobal fixture visibility #14567Expose
FixtureManager._register_fixtureas a stable publicpytest.register_fixtureinterface, for advanced use by plugins (also replaces internal uses in the python and unittest plugins).Fix #12376.