Dont clobber anchor when adding nodes - fixes #1269

pkg/yqlib/operator_add.go

@@ -56,7 +56,9 @@ func add(d *dataTreeNavigator, context Context, lhs *CandidateNode, rhs *Candida
 		return lhs.CreateReplacement(rhs.Node), nil
 	}
 
-	target := lhs.CreateReplacement(&yaml.Node{})
+	target := lhs.CreateReplacement(&yaml.Node{
+		Anchor: lhs.Node.Anchor,
+	})
 
 	switch lhsNode.Kind {
 	case yaml.MappingNode:

pkg/yqlib/operator_add_test.go

@@ -341,6 +341,15 @@ var addOperatorScenarios = []expressionScenario{
 			"D0, P[], (doc)::a: !horse [a, b]\nb: !goat [b]\n",
 		},
 	},
+	{
+		skipDoc:     true,
+		description: "Keep anchors",
+		document:    "a: &horse [1]",
+		expression:  `.a += 2`,
+		expected: []string{
+			"D0, P[], (doc)::a: &horse [1, 2]\n",
+		},
+	},
 }
 
 func TestAddOperatorScenarios(t *testing.T) {