AbstractMethodError: CometBroadcastExchangeExec missing sparkContext() from BroadcastExchangeLike

[dor-bernstein]

Describe the bug

When using Apache Comet 0.16 with Spark 3.5.6, queries that involve a broadcast exchange fail with:

java.lang.AbstractMethodError: Receiver class org.apache.spark.sql.comet.CometBroadcastExchangeExec
does not define or inherit an implementation of the resolved method
'abstract org.apache.spark.SparkContext org$apache$spark$sql$execution$exchange$BroadcastExchangeLike$$super$sparkContext()'
of interface org.apache.spark.sql.execution.exchange.BroadcastExchangeLike.

Steps to reproduce

1. Use Apache Comet 0.16 with Spark 3.5.6
2. Run a query that triggers a broadcast join / CometBroadcastExchangeExec

Expected behavior

CometBroadcastExchangeExec should correctly implement (or inherit) the sparkContext() method required by the BroadcastExchangeLike interface, and the query should execute successfully.

Additional context

Reported in apache/datafusion-comet#4125 alongside an unrelated Iceberg scan error. The original issue (reflection failure with AWS Glue) was resolved by the fix in #3895 (released in 0.16), but this new error surfaced afterward.

[mbutrovich]

Thanks for reporting @dor-bernstein! Do you have a minimal reproduction to help debug?