fixtures: order fixture override chains by visibility#14566
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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
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get_scope_packagewhen possible #14565The 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