FIX Metadata routing: register remainder when remainder="passthrough"#33665
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jeremiedbb merged 11 commits intoscikit-learn:mainfrom Apr 15, 2026
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Thanks for the PR @AnneBeyer
Co-authored-by: Jérémie du Boisberranger <jeremie@probabl.ai>
…om/AnneBeyer/scikit-learn into fix_metadata_remainder_passthrough
adrinjalali
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Apr 14, 2026
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| router = ct.get_metadata_routing() | ||
| if remainder == "drop": | ||
| assert "remainder" not in router._route_mappings | ||
| else: | ||
| assert "remainder" in router._route_mappings |
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I don't think you need this, the regression test is that fit_transform shouldn't raise a KeyError. Using this private attribute here in the test makes it fragile.
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Reference Issues/PRs
Closes #33614
What does this implement/fix? Explain your changes.
When
remainder="passthrough", it is now still registered in theMetadataRouter, even though it does not consume any meta data. (See the issue for details.)I added a test for all types of remainder values I could think of, which goes a bit beyond the "passthrough" issue here, but it helped me understand some of the ideas behind metadata routing. I'm happy to simplify it, though, if it is too much here.
@StefanieSenger @jinlow
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