Stop reconciling invalid PipelineRun

If a PipelineRun references a Pipeline that uses Tasks which don't
exist, we should immediately stop trying to Reconcile it. To fix this,
the user/trigger should create a new PipelineRun after creating the
Tasks needed.

pkg/reconciler/v1alpha1/pipelinerun/pipelinerun.go

@@ -171,7 +171,14 @@ func (c *Reconciler) reconcile(ctx context.Context, pr *v1alpha1.PipelineRun) er
 		p, pr.Name,
 	)
 	if err != nil {
-		return fmt.Errorf("error getting Tasks for Pipeline %s, Pipeline may be invalid!: %s", p.Name, err)
+		if errors.IsNotFound(err) {
+			c.Logger.Infof("PipelineRun %s's Pipeline %s can't be Run; it contains Tasks that don't exist: %s",
+				fmt.Sprintf("%s/%s", p.Namespace, p.Name),
+				fmt.Sprintf("%s/%s", p.Namespace, pr.Name), err)
+			// The PipelineRun is Invalid so we want to stop trying to Reconcile it
+			return nil
+		}
+		return fmt.Errorf("error getting Tasks and/or TaskRuns for Pipeline %s, Pipeline may be invalid!: %s", p.Name, err)
 	}
 	prtr := resources.GetNextTask(pr.Name, state, c.Logger)
 	if prtr != nil {

pkg/reconciler/v1alpha1/pipelinerun/pipelinerun_test.go

@@ -46,7 +46,6 @@ func TestReconcile(t *testing.T) {
 			},
 		},
 	}}
-
 	ps := []*v1alpha1.Pipeline{{
 		ObjectMeta: metav1.ObjectMeta{
 			Name:      "test-pipeline",
@@ -118,7 +117,7 @@ func TestReconcile(t *testing.T) {
 	}
 }
 
-func TestReconcileInvalid(t *testing.T) {
+func TestReconcile_InvalidPipeline(t *testing.T) {
 	prs := []*v1alpha1.PipelineRun{{
 		ObjectMeta: metav1.ObjectMeta{
 			Name:      "invalid-pipeline",
@@ -160,6 +159,40 @@ func TestReconcileInvalid(t *testing.T) {
 	}
 }
 
+func TestReconcile_MissingTasks(t *testing.T) {
+	ps := []*v1alpha1.Pipeline{{
+		ObjectMeta: metav1.ObjectMeta{
+			Name:      "pipeline-missing-tasks",
+			Namespace: "foo",
+		},
+		Spec: v1alpha1.PipelineSpec{Tasks: []v1alpha1.PipelineTask{{
+			Name:    "myspecialtask",
+			TaskRef: v1alpha1.TaskRef{Name: "sometask"},
+		}},
+		}},
+	}
+	prs := []*v1alpha1.PipelineRun{{
+		ObjectMeta: metav1.ObjectMeta{
+			Name:      "pipelinerun-missing-tasks",
+			Namespace: "foo",
+		},
+		Spec: v1alpha1.PipelineRunSpec{
+			PipelineRef: v1alpha1.PipelineRef{
+				Name: "pipeline-missing-tasks",
+			},
+		}},
+	}
+	d := testData{
+		prs: prs,
+		ps:  ps,
+	}
+	c, _, _ := getController(d)
+	err := c.Reconciler.Reconcile(context.Background(), "foo/pipelinerun-missing-tasks")
+	if err != nil {
+		t.Errorf("When Pipeline's Tasks can't be found, expected no error to be returned (i.e. controller should stop trying to reconcile) but got: %s", err)
+	}
+}
+
 func getLogMessages(logs *observer.ObservedLogs) []string {
 	messages := []string{}
 	for _, l := range logs.All() {

pkg/reconciler/v1alpha1/pipelinerun/resources/pipelinestate.go

@@ -85,9 +85,9 @@ func GetPipelineState(getTask GetTask, getTaskRun GetTaskRun, p *v1alpha1.Pipeli
 		pt := p.Spec.Tasks[i]
 		t, err := getTask(p.Namespace, pt.TaskRef.Name)
 		if err != nil {
-			return nil, fmt.Errorf("failed to get tasks for Pipeline %q: Error getting task %q : %s",
-				fmt.Sprintf("%s/%s", p.Namespace, p.Name),
-				fmt.Sprintf("%s/%s", p.Namespace, pt.TaskRef.Name), err)
+			// If the Task can't be found, it means the PipelineRun is invalid. Return the same error
+			// type so it can be used by the caller.
+			return nil, err
 		}
 		prtr := PipelineRunTaskRun{
 			Task:         t,

pkg/reconciler/v1alpha1/pipelinerun/resources/pipelinestate_test.go

@@ -17,7 +17,6 @@ limitations under the License.
 package resources
 
 import (
-	"fmt"
 	"testing"
 
 	"go.uber.org/zap"
@@ -255,7 +254,7 @@ func TestGetPipelineState(t *testing.T) {
 
 func TestGetPipelineState_TaskDoesntExist(t *testing.T) {
 	getTask := func(namespace, name string) (*v1alpha1.Task, error) {
-		return nil, fmt.Errorf("Task %s doesn't exist", name)
+		return nil, errors.NewNotFound(v1alpha1.Resource("task"), name)
 	}
 	getTaskRun := func(namespace, name string) (*v1alpha1.TaskRun, error) {
 		return nil, nil
@@ -264,6 +263,9 @@ func TestGetPipelineState_TaskDoesntExist(t *testing.T) {
 	if err == nil {
 		t.Fatalf("Expected error getting non-existent Tasks for Pipeline %s but got none", p.Name)
 	}
+	if !errors.IsNotFound(err) {
+		t.Fatalf("Expected same error type returned by func for non-existent Task for Pipeline %s but got %s", p.Name, err)
+	}
 }
 
 func TestGetPipelineConditionStatus(t *testing.T) {