Fix handling of multiple arguments in aggregate functions

This bug occurred when arguments were read for the GROUP BY sorter — all
arguments were incorrectly resolved to the first column. Added tests
confirm that aggregates now work correctly both with and without the
sorter.

core/translate/group_by.rs

@@ -479,7 +479,11 @@ impl<'a> GroupByAggArgumentSource<'a> {
                 dest_reg_start,
                 ..
             } => {
-                program.emit_column_or_rowid(*cursor_id, *col_start, dest_reg_start + arg_idx);
+                program.emit_column_or_rowid(
+                    *cursor_id,
+                    *col_start + arg_idx,
+                    dest_reg_start + arg_idx,
+                );
                 Ok(dest_reg_start + arg_idx)
             }
             GroupByAggArgumentSource::Register {

testing/agg-functions.test

@@ -143,4 +143,35 @@ do_execsql_test select-agg-json-array-object {
 
 do_execsql_test select-distinct-agg-functions {
 SELECT sum(distinct age), count(distinct age), avg(distinct age) FROM users;
-} {5050|100|50.5}
+} {5050|100|50.5}
+
+do_execsql_test select-json-group-object {
+  select price,
+         json_group_object(cast (id as text), name)
+  from products
+  group by price
+  order by price;
+} {1.0|{"9":"boots"}
+18.0|{"3":"shirt"}
+25.0|{"4":"sweater"}
+33.0|{"10":"coat"}
+70.0|{"6":"shorts"}
+74.0|{"5":"sweatshirt"}
+78.0|{"7":"jeans"}
+79.0|{"1":"hat"}
+81.0|{"11":"accessories"}
+82.0|{"2":"cap","8":"sneakers"}}
+
+do_execsql_test select-json-group-object-no-sorting-required {
+  select age,
+         json_group_object(cast (id as text), first_name)
+  from users
+  where first_name like 'Am%'
+  group by age
+  order by age
+  limit 5;
+} {1|{"6737":"Amy"}
+2|{"2297":"Amy","3580":"Amanda"}
+3|{"3437":"Amanda"}
+5|{"2378":"Amy","3227":"Amy","5605":"Amanda"}
+7|{"2454":"Amber"}}