fix(frontend): display_for_explain for ListValue (#7571)

I believe this bug was not caught before: #7541 because Array is treated as a function. But const_eval would force the Array to be evaluated into the List DataType

Anw, let's fix it as it's clearly a bug. After #7541, the new planner test will be evaluated as an List literal, rather than as FunctionCall as per now.

Approved-By: st1page

Co-Authored-By: jon-chuang <jon-chuang@users.noreply.github.com>
Co-Authored-By: jon-chuang <9093549+jon-chuang@users.noreply.github.com>

src/common/src/array/list_array.rs

@@ -297,12 +297,17 @@ impl Ord for ListValue {
 
 // Used to display ListValue in explain for better readibilty.
 pub fn display_for_explain(list: &ListValue) -> String {
-    // Example of ListValue display: ARRAY[1, 2]
+    // Example of ListValue display: ARRAY[1, 2, null]
     format!(
         "ARRAY[{}]",
         list.values
             .iter()
-            .map(|v| v.as_ref().unwrap().as_scalar_ref_impl().to_text())
+            .map(|v| {
+                match v.as_ref() {
+                    None => "null".into(),
+                    Some(scalar) => scalar.as_scalar_ref_impl().to_text(),
+                }
+            })
             .collect::<Vec<String>>()
             .join(", ")
     )

src/frontend/planner_test/tests/testdata/expr.yaml

@@ -532,3 +532,9 @@
   binder_error: |-
     Feature is not yet implemented: unsupported function "pg_teminate_backend", do you mean "pg_terminate_backend"?
     Tracking issue: https://github.com/risingwavelabs/risingwave/issues/112
+- name: regression (#7571) - literal debug display for array with NULL values
+  sql: |
+    select ARRAY[1, null] t;
+  logical_plan: |
+    LogicalProject { exprs: [Array(1:Int32, null:Int32)] }
+    └─LogicalValues { rows: [[]], schema: Schema { fields: [] } }

src/frontend/planner_test/tests/testdata/shared_views.yaml

@@ -1,3 +1,4 @@
+# This file is automatically generated. See `src/frontend/planner_test/README.md` for more information.
 - sql: |
     create table t1 (x int, y int);
     create view v1 as select x + y as z from t1 where y > 0;
@@ -39,4 +40,4 @@
                 └─StreamShare { id = 207 }
                   └─StreamProject { exprs: [(t1.x + t1.y), t1._row_id] }
                     └─StreamFilter { predicate: (t1.y > 0:Int32) }
-                      └─StreamTableScan { table: t1, columns: [t1.x, t1.y, t1._row_id], pk: [t1._row_id], dist: UpstreamHashShard(t1._row_id) }
+                      └─StreamTableScan { table: t1, columns: [t1.x, t1.y, t1._row_id], pk: [t1._row_id], dist: UpstreamHashShard(t1._row_id) }