resources: Fail on non-string template labels.

Although ObjectMeta defines labels as a map[string]string, Unstructured
types allow for map[string]interface{}, which means that users can set
non-string values like ints in their configurations, and we will parse it
with no issues.

We discovered that the behavior of
[unstructured.GetLabels](https://github.com/kubernetes/apimachinery/blob/dd12c7a65e7f49c4e00b5bd5eb93de2fcbf7831d/pkg/apis/meta/v1/unstructured/unstructured.go#L395)
will silently ignore errors, returning an empty label set if a
non-string value is included. When used in triggers, this looks like we
are completely ignoring the user provided labels.

This change replaces GetLabels with it's underlying implementation, and bubbles
back the non-string error if it is encountered.

pkg/resources/create.go

@@ -70,11 +70,14 @@ func Create(logger *zap.SugaredLogger, rt json.RawMessage, triggerName, eventID,
 		return fmt.Errorf("couldn't unmarshal json from the TriggerTemplate: %v", err)
 	}
 
-	data = addLabels(data, map[string]string{
+	data, err := addLabels(data, map[string]string{
 		triggersv1.EventListenerLabelKey: elName,
 		triggersv1.EventIDLabelKey:       eventID,
 		triggersv1.TriggerLabelKey:       triggerName,
 	})
+	if err != nil {
+		return err
+	}
 
 	namespace := data.GetNamespace()
 	// Default the resource creation to the EventListenerNamespace if not found in the resource template
@@ -112,8 +115,12 @@ func Create(logger *zap.SugaredLogger, rt json.RawMessage, triggerName, eventID,
 }
 
 // addLabels adds autogenerated Tekton labels to created resources.
-func addLabels(us *unstructured.Unstructured, labelsToAdd map[string]string) *unstructured.Unstructured {
-	labels := us.GetLabels()
+func addLabels(us *unstructured.Unstructured, labelsToAdd map[string]string) (*unstructured.Unstructured, error) {
+	labels, _, err := unstructured.NestedStringMap(us.Object, "metadata", "labels")
+	if err != nil {
+		return nil, err
+	}
+
 	if labels == nil {
 		labels = make(map[string]string)
 	}
@@ -123,5 +130,5 @@ func addLabels(us *unstructured.Unstructured, labelsToAdd map[string]string) *un
 	}
 
 	us.SetLabels(labels)
-	return us
+	return us, nil
 }

pkg/resources/create_test.go

@@ -299,10 +299,28 @@ func Test_AddLabels(t *testing.T) {
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			got := addLabels(tt.us, tt.labelsToAdd)
+			got, err := addLabels(tt.us, tt.labelsToAdd)
+			if err != nil {
+				t.Fatal(err)
+			}
 			if diff := cmp.Diff(tt.want, got); diff != "" {
 				t.Errorf("addLabels(): -want +got: %s", diff)
 			}
 		})
 	}
+
+	t.Run("non-string label", func(t *testing.T) {
+		in := &unstructured.Unstructured{
+			Object: map[string]interface{}{
+				"metadata": map[string]interface{}{
+					"labels": map[string]interface{}{
+						"foo": 0,
+					},
+				},
+			},
+		}
+		if got, err := addLabels(in, map[string]string{"a": "b"}); err == nil {
+			t.Errorf("expected error, got: %v", got)
+		}
+	})
 }