Fixed handling of nulls with sort_by expressions #2164

Author: mikefarah

pkg/yqlib/operator_sort.go

@@ -69,6 +69,7 @@ func (a sortableNodeArray) Less(i, j int) bool {
 	rhsContext := a[j].CompareContext
 
 	rhsEl := rhsContext.MatchingNodes.Front()
+
 	for lhsEl := lhsContext.MatchingNodes.Front(); lhsEl != nil && rhsEl != nil; lhsEl = lhsEl.Next() {
 		lhs := lhsEl.Value.(*CandidateNode)
 		rhs := rhsEl.Value.(*CandidateNode)
@@ -83,7 +84,7 @@ func (a sortableNodeArray) Less(i, j int) bool {
 
 		rhsEl = rhsEl.Next()
 	}
-	return false
+	return lhsContext.MatchingNodes.Len() < rhsContext.MatchingNodes.Len()
 }
 
 func (a sortableNodeArray) compare(lhs *CandidateNode, rhs *CandidateNode, dateTimeLayout string) int {

pkg/yqlib/operator_sort_test.go

@@ -21,6 +21,17 @@ var sortByOperatorScenarios = []expressionScenario{
 			"D0, P[0], (!!map)::{a: banana}\n",
 		},
 	},
+	{
+		description: "Sort by with null",
+		skipDoc:     true,
+		document:    "[{a: banana},null,{a: apple}]",
+		expression:  `sort_by(.a)[]`,
+		expected: []string{
+			"D0, P[1], (!!null)::null\n",
+			"D0, P[2], (!!map)::{a: apple}\n",
+			"D0, P[0], (!!map)::{a: banana}\n",
+		},
+	},
 	{
 		description: "Sort by multiple fields",
 		document:    "[{a: dog},{a: cat, b: banana},{a: cat, b: apple}]",