fix(pandas): apply parsers to Index fields and schema components - #2435
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Signed-off-by: Sebastian Cao <cycsmail@gmail.com>
cosmicBboy
approved these changes
Aug 4, 2026
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Fixes #1684
Problem
@pa.parseron a field annotated asIndexis silently ignored:Two things cause this.
FieldInfo.index_propertiesnever forwards the field's parsers, soIndexcomponents built from aDataFrameModeldon't have them at all. And even withparserspassed directly topa.Index, the index backend validates a series copy of the index and discards the parsed result, while coercion runs before parsers, so a parser that cleans raw values into a coercible form never gets a chance (the same ordering issue #2047 fixed for columns).This forwards
parsersinFieldInfo.index_properties, writes the validated series back tocheck_obj.indexinIndexBackendwhen the schema has parsers, and defers index coercion (index-level and dataframe-level) to the array backend when parsers are present, so they run before dtype coercion like they do for columns. Added regression tests intests/pandas/test_parsers.pyfor the modelIndexfield case from the issue, parsers on apa.Indexinside aDataFrameSchema, and an index parser whose output needs coercion.