Bubble up the image related error reason to taskrun status

When pod is pending because of failure of pulling image the users
can not get the clear reason or message from the taskrun status.

Now I will check the pod status and judge if the error is caused
by image if so the error reason and message will bubble up to
taskrun status. Then user can know what happend though the taskrun
status.

Related issue: tektoncd#4802

Signed-off-by: yuzhipeng <yuzp1996@qq.com>

pkg/pod/status.go

@@ -53,6 +53,9 @@ const (
 	// to resource constraints on the node
 	ReasonExceededNodeResources = "ExceededNodeResources"
 
+	// ReasonPullImageFailed indicates that the TaskRun's pod failed to pull image
+	ReasonPullImageFailed = "PullImageFailed"
+
 	// ReasonCreateContainerConfigError indicates that the TaskRun failed to create a pod due to
 	// config error of container
 	ReasonCreateContainerConfigError = "CreateContainerConfigError"
@@ -314,6 +317,8 @@ func updateIncompleteTaskRunStatus(trs *v1beta1.TaskRunStatus, pod *corev1.Pod)
 			markStatusRunning(trs, ReasonExceededNodeResources, "TaskRun Pod exceeded available resources")
 		case isPodHitConfigError(pod):
 			markStatusFailure(trs, ReasonCreateContainerConfigError, "Failed to create pod due to config error")
+		case isPullImageError(pod):
+			markStatusRunning(trs, ReasonPullImageFailed, getWaitingMessage(pod))
 		default:
 			markStatusRunning(trs, ReasonPending, getWaitingMessage(pod))
 		}
@@ -408,6 +413,34 @@ func isPodHitConfigError(pod *corev1.Pod) bool {
 	return false
 }
 
+// isPullImageError returns true if the Pod's status indicates there are any error when pulling image
+func isPullImageError(pod *corev1.Pod) bool {
+	for _, containerStatus := range pod.Status.ContainerStatuses {
+		if containerStatus.State.Waiting != nil && isImageErrorReason(containerStatus.State.Waiting.Reason) {
+			return true
+		}
+	}
+	return false
+}
+
+func isImageErrorReason(reason string) bool {
+	// Reference from https://github.com/kubernetes/kubernetes/blob/master/pkg/kubelet/images/types.go#L26
+	imageErrorReasons := []string{
+		"ImagePullBackOff",
+		"ImageInspectError",
+		"ErrImagePull",
+		"ErrImageNeverPull",
+		"RegistryUnavailable",
+		"InvalidImageName",
+	}
+	for _, imageReason := range imageErrorReasons {
+		if imageReason == reason {
+			return true
+		}
+	}
+	return false
+}
+
 func getWaitingMessage(pod *corev1.Pod) string {
 	// First, try to surface reason for pending/unknown about the actual build step.
 	for _, status := range pod.Status.ContainerStatuses {