Details
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Bug
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Status: Patch Available
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Major
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Resolution: Unresolved
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None
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None
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Description
Python's validator silently accepts (generic) records with extra fields and considers them valid.
For example, io.validate silently considers that the schema:
{"type": "record",
"name": "Test",
"fields": [{"name": "f", "type": "long"}]}
should accept records like:
{'f': 5, 'extra_field': "abc"}
but this is problematic.
This is especially problematic for encoding unions, because internally the Python serializer uses validate to find the appropriate schema with which to encode a given object.
In the current implementation, union schema selection is the last schema that validate(schema, obj) returns True for. If validate isn't picky, this encoding will frequently guess wrong.
I will attach two patches: one to the tests and one to the validate function.