avro schema reader ignores iceberg-field-name property — returns sanitized names from java manifests #2536

problem

when java writes manifests with partition field names that violate avro naming rules, it sanitizes them (e.g. 815d3b... → _815d3b...) and stores the original in an iceberg-field-name avro field property. iceberg-rust's avro reader uses the avro field name directly without checking this property, so it returns the sanitized name instead of the original.

this causes field name mismatches when reading java-written manifests — the partition field name in the manifest entry won't match the partition field name in the table's partition spec.

relevant code

crates/iceberg/src/avro/schema.rs — avro_schema_to_schema reads &avro_field.name without checking for iceberg-field-name custom property.

java's read path resolves fields by field-id (integer), but also provides the original name via ICEBERG_FIELD_NAME_PROP:

public static final String ICEBERG_FIELD_NAME_PROP = "iceberg-field-name";

reproduction

1. create a table in java with a partition field name starting with a digit
2. write data (java produces manifests with sanitized avro field names + iceberg-field-name property)
3. read the manifest in iceberg-rust — field names will be the sanitized form, not the original

expected behavior

when reading avro schemas from manifests, check each field for the iceberg-field-name property. if present, use that as the iceberg field name instead of the avro field name.

notes

• iceberg resolves fields by field-id in most paths, so the impact is limited to code that uses field names from manifest entries
• this is a well-established convention in the java implementation (since 2019)
• pyiceberg implements its own avro reader that bypasses name validation entirely