Fixed string, null concact consistency #1712

pkg/yqlib/operator_add.go

@@ -107,7 +107,11 @@ func addScalars(context Context, target *CandidateNode, lhs *yaml.Node, rhs *yam
 
 	} else if lhsTag == "!!str" {
 		target.Node.Tag = lhs.Tag
-		target.Node.Value = lhs.Value + rhs.Value
+		if rhsTag == "!!null" {
+			target.Node.Value = lhs.Value
+		} else {
+			target.Node.Value = lhs.Value + rhs.Value
+		}
 	} else if rhsTag == "!!str" {
 		target.Node.Tag = rhs.Tag
 		target.Node.Value = lhs.Value + rhs.Value

pkg/yqlib/operator_add_test.go

@@ -225,6 +225,20 @@ var addOperatorScenarios = []expressionScenario{
 			"D0, P[], (!cool)::3cat\n",
 		},
 	},
+	{
+		skipDoc:    true,
+		expression: `null + "cat"`,
+		expected: []string{
+			"D0, P[], (!!str)::cat\n",
+		},
+	},
+	{
+		skipDoc:    true,
+		expression: `"cat" + null`,
+		expected: []string{
+			"D0, P[], (!!str)::cat\n",
+		},
+	},
 	{
 		description:    "Number addition - float",
 		subdescription: "If the lhs or rhs are floats then the expression will be calculated with floats.",