handling cast in agg to not cause null columns (finos#3831)

Author: ahallgs

legend-engine-core/legend-engine-core-pure/legend-engine-pure-code-functions-relation/legend-engine-pure-functions-relation-pure/src/main/resources/core_functions_relation/relation/tests/composition.pure

@@ -409,3 +409,65 @@ function <<PCT.test, PCTRelationQualifier.relation, PCTRelationQualifier.olap>>
                   '   Peter,Smith,null,Johnson\n'+
                   '#', $res->toString());
 }
+
+function <<PCT.test, PCTRelationQualifier.relation, PCTRelationQualifier.aggregation>> meta::pure::functions::relation::tests::composition::testGroupByCastBeforeAgg<T|m>(f:Function<{Function<{->T[m]}>[1]->T[m]}>[1]):Boolean[1]
+{
+  let expr = {
+              | #TDS
+                id, grp
+                1, 2
+                2, 1
+                3, 3
+                4, 4
+                5, 2
+                6, 1
+                7, 3
+                8, 1
+                9, 5
+                10, 0
+              #->groupBy(~grp, ~newCol:x|$x.id:x|$x->cast(@Integer)->plus())
+              };
+
+  let res = $f->eval($expr);
+
+  assertEquals( '#TDS\n'+
+                '   grp,newCol\n'+
+                '   0,10\n'+
+                '   1,16\n'+
+                '   2,6\n'+
+                '   3,10\n'+
+                '   4,4\n'+
+                '   5,9\n'+
+                '#', $res->sort(~grp->ascending())->toString());
+}
+
+function <<PCT.test, PCTRelationQualifier.relation, PCTRelationQualifier.aggregation>> meta::pure::functions::relation::tests::composition::testGroupByCastAfterAgg<T|m>(f:Function<{Function<{->T[m]}>[1]->T[m]}>[1]):Boolean[1]
+{
+  let expr = {
+              | #TDS
+                id, grp
+                1, 2
+                2, 1
+                3, 3
+                4, 4
+                5, 2
+                6, 1
+                7, 3
+                8, 1
+                9, 5
+                10, 0
+              #->groupBy(~grp, ~newCol:x|$x.id:x|$x->plus()->cast(@Integer))
+              };
+
+  let res = $f->eval($expr);
+
+  assertEquals( '#TDS\n'+
+                '   grp,newCol\n'+
+                '   0,10\n'+
+                '   1,16\n'+
+                '   2,6\n'+
+                '   3,10\n'+
+                '   4,4\n'+
+                '   5,9\n'+
+                '#', $res->sort(~grp->ascending())->toString());
+}

legend-engine-xts-relationalStore/legend-engine-xt-relationalStore-generation/legend-engine-xt-relationalStore-pure/legend-engine-xt-relationalStore-core-pure/src/main/resources/core_relational/relational/pureToSQLQuery/pureToSQLQuery.pure

@@ -5236,7 +5236,7 @@ function meta::relational::functions::pureToSqlQuery::processAggFn(v:ValueSpecif
          e:RoutedValueSpecification[1]|$e.value->processAggFn($params, $state),
          f:FunctionExpression[1] |
                if($f.func == cast_Any_m__T_1__T_m_,
-                  | $f.parametersValues->at(1)->cast(@ValueSpecification)->processAggFn($params, $state),
+                  | $f.parametersValues->at(0)->processAggFn($params, $state),
                   | let fn = $f.func.functionName->toOne();
                     let singleArgument = $f.parametersValues->match([
                       i:InstanceValue[1] | $i.values->size() == 1,