What changes were proposed in this pull request?

This PR updates TableOutputResolver so INSERT WITH SCHEMA EVOLUTION by position does not auto-fill trailing generated columns. If a by-position insert omits a trailing generated column, Spark now throws the same arity mismatch error as a regular by-position insert.

The PR also adds coverage that:

• by-position INSERT WITH SCHEMA EVOLUTION rejects an omitted trailing generated column;
• by-name INSERT WITH SCHEMA EVOLUTION with an explicit column list still auto-fills the generated column.

Why are the changes needed?

By-position writes require values for all target columns. Generated columns are special because users can omit them only through by-name writes with an explicit column list, where Spark can unambiguously identify the stored input columns used by the generation expression.

Without this change, the by-position schema-evolution path could auto-fill a trailing generated column, making it inconsistent with regular by-position inserts and with Delta behavior.

Does this PR introduce any user-facing change?

Yes. In the current unreleased behavior, a by-position INSERT WITH SCHEMA EVOLUTION could omit a trailing generated column and have Spark auto-fill it. After this change, that insert fails with INSERT_COLUMN_ARITY_MISMATCH.NOT_ENOUGH_DATA_COLUMNS. Users can still omit generated columns with a by-name insert and an explicit column list.

How was this patch tested?

Added a regression test in GeneratedColumnWriteSuite.

Ran:

MAVEN_MIRROR_URL=https://maven-proxy.cloud.databricks.com build/sbt 'sql/testOnly org.apache.spark.sql.connector.GeneratedColumnWriteSuite -- -z "INSERT WITH SCHEMA EVOLUTION by position does not auto-fill trailing generated column"'

Was this patch authored or co-authored using generative AI tooling?

Generated-by: OpenAI Codex (GPT-5)