chore: promote array_insert to compatible and consolidate expression docs (#4065)

Author: andygrove

.claude/skills/audit-comet-expression/SKILL.md

@@ -311,17 +311,16 @@ After implementing tests, tell the user how to run them:
 
 ---
 
-## Step 8: Update the Expression Audit Log
+## Step 8: Update the Expression Support Doc
 
-After completing the audit (whether or not tests were added), append a row to the audit log at
-`docs/source/contributor-guide/expression-audit-log.md`.
+After completing the audit (whether or not tests were added), add sub-bullets under the expression's
+entry in `docs/source/contributor-guide/spark_expressions_support.md`.
 
-The row should include:
+Add one sub-bullet per Spark version checked, each including:
 
-- Expression name
-- Spark versions checked (e.g. 3.4.3, 3.5.8, 4.0.1)
+- Spark version (e.g. 3.4.3, 3.5.8, 4.0.1)
 - Today's date
-- A brief summary of findings (behavioral differences, bugs found/fixed, tests added, known incompatibilities)
+- A brief note for any version-specific finding (behavioral difference, known incompatibility); omit if nothing notable
 
 ---
 

docs/source/contributor-guide/adding_a_new_expression.md

@@ -25,7 +25,7 @@ Before you start, have a look through [these slides](https://docs.google.com/pre
 
 ## Finding an Expression to Add
 
-You may have a specific expression in mind that you'd like to add, but if not, you can review the [expression coverage document](https://github.com/apache/datafusion-comet/blob/main/docs/spark_expressions_support.md) to see which expressions are not yet supported.
+You may have a specific expression in mind that you'd like to add, but if not, you can review the [expression coverage document](spark_expressions_support.md) to see which expressions are not yet supported.
 
 ## Implementing the Expression
 

docs/source/contributor-guide/expression-audit-log.md

@@ -33,6 +33,7 @@ Debugging Guide <debugging>
 Benchmarking Guide <benchmarking>
 Adding a New Operator <adding_a_new_operator>
 Adding a New Expression <adding_a_new_expression>
+Supported Spark Expressions <spark_expressions_support>
 Tracing <tracing>
 Profiling <profiling>
 Spark SQL Tests <spark-sql-tests.md>

docs/source/contributor-guide/index.md

@@ -89,6 +89,9 @@
 - [x] array_distinct
 - [x] array_except
 - [x] array_insert
+  - Spark 3.4.3 audited 2026-04-02
+  - Spark 3.5.8 audited 2026-04-02
+  - Spark 4.0.1 audited 2026-04-02 (pos=0 error message differs from Spark)
 - [x] array_intersect
 - [x] array_join
 - [x] array_max

docs/spark_expressions_support.md …butor-guide/spark_expressions_support.mddocs/spark_expressions_support.md renamed to docs/source/contributor-guide/spark_expressions_support.md docs/spark_expressions_support.md renamed to docs/source/contributor-guide/spark_expressions_support.md

@@ -245,7 +245,7 @@ Comet supports using the following aggregate functions within window contexts wi
 | ArrayDistinct  | Yes               |                                                       |
 | ArrayExcept    | No                |                                                       |
 | ArrayFilter    | Yes               | Only supports case where function is `IsNotNull`      |
-| ArrayInsert    | No                |                                                       |
+| ArrayInsert    | Yes               |                                                       |
 | ArrayIntersect | No                |                                                       |
 | ArrayJoin      | No                |                                                       |
 | ArrayMax       | Yes               |                                                       |

docs/source/user-guide/latest/expressions.md

@@ -390,7 +390,7 @@ object CometArrayJoin extends CometExpressionSerde[ArrayJoin] {
 
 object CometArrayInsert extends CometExpressionSerde[ArrayInsert] {
 
-  override def getSupportLevel(expr: ArrayInsert): SupportLevel = Incompatible(None)
+  override def getSupportLevel(expr: ArrayInsert): SupportLevel = Compatible()
 
   override def convert(
       expr: ArrayInsert,