Fetch resource metadata from unstructured

In sink.createResource, we need access to resource metadata such as
name, namespace, apiVersion, and kind from the raw json template. We
were using gjson.GetBytes to do this. However, later in the function
we were also unmarshalling the raw template to
`unstructured.Unstructured` which already has methods for accessing
all of the required metadata.

This commit refactors the createResource function to first umarshall
the raw template to unstructured and then get all of the metadata we
need from that object.  This was also the only place where we were
using gjson so, as a side effect we can now remove our dependency on
the GJson library.

Signed-off-by: Dibyo Mukherjee <dibyo@google.com>

pkg/sink/sink.go

@@ -28,7 +28,6 @@ import (
 
 	"github.com/tektoncd/triggers/pkg/interceptors"
 
-	"github.com/tidwall/gjson"
 	"github.com/tidwall/sjson"
 	"golang.org/x/xerrors"
 
@@ -163,43 +162,46 @@ func (r Sink) createResources(resources []json.RawMessage, triggerName, eventID
 // createResource uses the kubeClient to create the resource defined in the
 // TriggerResourceTemplate and returns any errors with this process
 func (r Sink) createResource(rt json.RawMessage, triggerName string, eventID string) error {
+	// Add common labels
+	rt, err := addLabels(rt, map[string]string{
+		triggersv1.EventListenerLabelKey: r.EventListenerName,
+		triggersv1.EventIDLabelKey:       eventID,
+		triggersv1.TriggerLabelKey:       triggerName,
+	})
+	if err != nil {
+		return err
+	}
+
 	// Assume the TriggerResourceTemplate is valid (it has an apiVersion and Kind)
-	apiVersion := gjson.GetBytes(rt, "apiVersion").String()
-	kind := gjson.GetBytes(rt, "kind").String()
-	namespace := gjson.GetBytes(rt, "metadata.namespace").String()
+	data := new(unstructured.Unstructured)
+	if err := data.UnmarshalJSON(rt); err != nil {
+		return err
+	}
+
+	namespace := data.GetNamespace()
 	// Default the resource creation to the EventListenerNamespace if not found in the resource template
 	if namespace == "" {
 		namespace = r.EventListenerNamespace
 	}
 
 	// Resolve resource kind to the underlying API Resource type.
-	apiResource, err := r.findAPIResource(apiVersion, kind)
+	apiResource, err := r.findAPIResource(data.GetAPIVersion(), data.GetKind())
 	if err != nil {
 		return err
 	}
 
-	rt, err = addLabels(rt, map[string]string{
-		triggersv1.EventListenerLabelKey: r.EventListenerName,
-		triggersv1.EventIDLabelKey:       eventID,
-		triggersv1.TriggerLabelKey:       triggerName,
-	})
-	if err != nil {
-		return err
+	name := data.GetName()
+	if name == "" {
+		name = data.GetGenerateName()
 	}
-
-	resourcename := gjson.GetBytes(rt, "metadata.name")
-	r.Logger.Infof("Generating resource: kind: %+v, name: %s", apiResource, resourcename)
+	r.Logger.Infof("Generating resource: kind: %+v, name: %s", apiResource, name)
 
 	gvr := schema.GroupVersionResource{
 		Group:    apiResource.Group,
 		Version:  apiResource.Version,
 		Resource: apiResource.Name,
 	}
 
-	data := new(unstructured.Unstructured)
-	if err := data.UnmarshalJSON(rt); err != nil {
-		return err
-	}
 	_, err = r.DynamicClient.Resource(gvr).Namespace(namespace).Create(data, metav1.CreateOptions{})
 	return err
 }