Fixed #1048

pkg/yqlib/operator_union.go

@@ -1,5 +1,7 @@
 package yqlib
 
+import "container/list"
+
 func unionOperator(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {
 	log.Debug("unionOperator")
 	log.Debug("context: %v", NodesToString(context.MatchingNodes))
@@ -18,19 +20,25 @@ func unionOperator(d *dataTreeNavigator, context Context, expressionNode *Expres
 	log.Debug("lhs: %v", lhs.ToString())
 	log.Debug("rhs: %v", rhs.ToString())
 
+	results := lhs.ChildContext(list.New())
+	for el := lhs.MatchingNodes.Front(); el != nil; el = el.Next() {
+		node := el.Value.(*CandidateNode)
+		results.MatchingNodes.PushBack(node)
+	}
+
 	// this can happen when both expressions modify the context
 	// instead of creating their own.
 	/// (.foo = "bar"), (.thing = "cat")
-
 	if rhs.MatchingNodes != lhs.MatchingNodes {
 
 		for el := rhs.MatchingNodes.Front(); el != nil; el = el.Next() {
 			node := el.Value.(*CandidateNode)
 			log.Debug("processing %v", NodeToString(node))
 
-			lhs.MatchingNodes.PushBack(node)
+			results.MatchingNodes.PushBack(node)
 		}
 	}
-	log.Debug("all together: %v", lhs.ToString())
-	return lhs, nil
+	log.Debug("and lets print it out")
+	log.Debug("all together: %v", results.ToString())
+	return results, nil
 }

pkg/yqlib/operator_union_test.go

@@ -13,6 +13,14 @@ var unionOperatorScenarios = []expressionScenario{
 			"D0, P[], (doc)::{}\n",
 		},
 	},
+	{
+		skipDoc:     true,
+		description: "clone test",
+		expression:  `"abc" as $a | [$a, "cat"]`,
+		expected: []string{
+			"D0, P[], (!!seq)::- abc\n- cat\n",
+		},
+	},
 	{
 		skipDoc:    true,
 		expression: `(.foo = "bar"), (.toe = "jam")`,