Avro read fails with ResolveError when the file has a map/list/struct field not in the read schema #4288

Apache Iceberg version

0.12.0 (latest release); also reproduced on main (e3564a5)

Please describe the bug 🐞

Reading an Avro file fails with ResolveError when the file schema has a map, list, or struct field that is not in the read schema:

pyiceberg.exceptions.ResolveError: File/read schema are not aligned for map, got None
  at pyiceberg/avro/resolver.py  SchemaPartnerAccessor.map_key_partner

Why this matters: The spec resolves fields by ID and asks readers to be permissive: its manifest read rules say a field the reader's version doesn't define should be ignored ("Ignore the field"). Iceberg Java/Spark, DuckDB, and Snowflake skip unknown manifest fields of any type. PyIceberg skips them only when they are primitives, so a manifest with an extra nested field makes the table unreadable. For example, a data_file map field that the reader's version doesn't define fails the scan.

Cause: ReadSchemaResolver.struct gives a file-only primitive a None position, so it is read and dropped. For nested types, though, SchemaPartnerAccessor.field_partner, list_element_partner, map_key_partner, and map_value_partner raise when the partner is None.

Minimal reproduction: write a manifest entry with fastavro, using MANIFEST_ENTRY_SCHEMAS[2] plus an extra optional map<int, binary> field in data_file. Then read it with AvroFile(read_schema=MANIFEST_ENTRY_SCHEMAS[2], ...).

Willingness to contribute

• I can contribute a fix for this bug independently