[native_datafusion] [Spark SQL Tests] input_file_name() returns empty string #3312

Summary

3 Spark SQL tests fail because input_file_name() returns an empty string when native_datafusion scan is used.

Failing Tests

• UDFSuite: "SPARK-8005 input_file_name"
• ColumnExpressionSuite: "input_file_name, input_file_block_start, input_file_block_length - FileScanRDD"
• ExtractPythonUDFsSuite: "Python UDF should not break column pruning/filter pushdown -- Parquet V1"

Root Cause

native_datafusion scan doesn't populate the input_file_name() / input_file_block_start() / input_file_block_length() metadata that Spark's FileSourceScanExec provides. This is a functional gap.

Possible Fix

In CometScanRule.nativeDataFusionScan(), detect when the query references InputFileName, InputFileBlockStart, or InputFileBlockLength expressions and fall back to native_iceberg_compat.

Related

Discovered in CI for #3307 (enable native_datafusion in auto scan mode).