store: Fix handling of enum arrays

Roundtripping arrays of enums would fail because we would read an array of
enums back as a single string "{yellow,red,BLUE}" instead of the array
["yellow", "red", "BLUE"]. Storing an update to such an entity, even if
users make no changes to that field, would fail because Postgres expects an
array and we were sending a scalar value.

This fixes a bug introduced in PR
#5372

store/postgres/src/relational/dsl.rs

@@ -322,7 +322,8 @@ impl<'a> Table<'a> {
             table: &'b Table<'b>,
             column: &'b RelColumn,
         ) {
-            let name = format!("{}.{}::text", table.alias.as_str(), &column.name);
+            let cast = if column.is_list() { "text[]" } else { "text" };
+            let name = format!("{}.{}::{}", table.alias.as_str(), &column.name, cast);
 
             match (column.is_list(), column.is_nullable()) {
                 (true, true) => select.add_field(sql::<Nullable<Array<Text>>>(&name)),

store/test-store/tests/postgres/relational.rs

@@ -167,6 +167,13 @@ const THINGS_GQL: &str = r#"
         id: Bytes!,
         name: String!
     }
+
+    # For testing handling of enums and enum arrays
+    type Spectrum @entity {
+        id: ID!,
+        main: Color!
+        all: [Color!]!
+    }
 "#;
 
 lazy_static! {
@@ -739,6 +746,41 @@ fn serialize_bigdecimal() {
     });
 }
 
+#[test]
+fn enum_arrays() {
+    // We had an issue where we would read an array of enums back as a
+    // single string; for this test, we would get back the string
+    // "{yellow,red,BLUE}" instead of the array ["yellow", "red", "BLUE"]
+    run_test(|conn, layout| {
+        let spectrum = entity! { THINGS_SCHEMA =>
+            id: "rainbow",
+            main: "yellow",
+            all: vec!["yellow", "red", "BLUE"]
+        };
+
+        insert_entity(
+            conn,
+            layout,
+            &THINGS_SCHEMA.entity_type("Spectrum").unwrap(),
+            vec![spectrum.clone()],
+        );
+
+        let actual = layout
+            .find(
+                conn,
+                &THINGS_SCHEMA
+                    .entity_type("Spectrum")
+                    .unwrap()
+                    .parse_key("rainbow")
+                    .unwrap(),
+                BLOCK_NUMBER_MAX,
+            )
+            .expect("Failed to read Spectrum[rainbow]")
+            .unwrap();
+        assert_entity_eq!(spectrum, actual);
+    });
+}
+
 fn count_scalar_entities(conn: &mut PgConnection, layout: &Layout) -> usize {
     let filter = EntityFilter::Or(vec![
         EntityFilter::Equal("bool".into(), true.into()),