avro-missing-reader-field-requires-default

Status: IN

During record resolution, a reader field absent from the writer schema must have a default value; missing defaults cause SchemaCompatibilityError, making defaults the mechanism for forward/backward compatibility.

Source: entries/2026/05/29/avro-serializer-avro_serializer.md

Example

if rf["name"] not in writer_data:
    if "default" not in rf:
        raise SchemaCompatibilityError(
            f"Reader field {rf[\"name\"]} has no default")

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