Referencing StepActions in Steps

This PR allows the Step to reference a StepAction CRD deployed on the cluster. This capability is gated behind a feature flag `enable-step-actions`.  Remote resolution of StepActions will be implemented in a follow-up PR.

This is the second item on the implementation Issue tektoncd#7259

docs/stepactions.md

@@ -135,3 +135,87 @@ spec:
         timeout: 1h
         onError: continue
 ```
+
+## Referencing a StepAction
+
+`StepActions` can be referenced from the `Step` using the `ref` field, as follows:
+
+```yaml
+apiVersion: tekton.dev/v1
+kind: TaskRun
+metadata:
+  name: step-action-run
+spec:
+  TaskSpec:
+    steps:
+      - name: action-runner
+        ref:
+          name: step-action
+```
+
+Upon resolution and execution of the `TaskRun`, the `Status` will look something like:
+
+```yaml
+status:
+  completionTime: "2023-10-24T20:28:42Z"
+  conditions:
+  - lastTransitionTime: "2023-10-24T20:28:42Z"
+    message: All Steps have completed executing
+    reason: Succeeded
+    status: "True"
+    type: Succeeded
+  podName: step-action-run-pod
+  provenance:
+    featureFlags:
+      EnableStepActions: true
+      ...
+  startTime: "2023-10-24T20:28:32Z"
+  steps:
+  - container: step-action-runner
+    imageID: docker.io/library/alpine@sha256:eece025e432126ce23f223450a0326fbebde39cdf496a85d8c016293fc851978
+    name: action-runner
+    terminated:
+      containerID: containerd://46a836588967202c05b594696077b147a0eb0621976534765478925bb7ce57f6
+      exitCode: 0
+      finishedAt: "2023-10-24T20:28:42Z"
+      reason: Completed
+      startedAt: "2023-10-24T20:28:42Z"
+  taskSpec:
+    steps:
+    - computeResources: {}
+      image: alpine
+      name: action-runner
+      script: |
+        echo "I am a Step Action!!!"
+```
+
+If a `Step` is referencing a `StepAction`, it cannot contain the fields supported by `StepActions`. This includes:
+- `image`
+- `command`
+- `args`
+- `script`
+- `env`
+
+Using any of the above fields and referencing a `StepAction` in the same `Step` is not allowed and will cause an validation error.
+
+```yaml
+# This is not allowed and will result in a validation error.
+# Because the image is expected to be provided by the StepAction
+# and not inlined.
+apiVersion: tekton.dev/v1
+kind: TaskRun
+metadata:
+  name: step-action-run
+spec:
+  TaskSpec:
+    steps:
+      - name: action-runner
+        ref:
+          name: step-action
+        image: ubuntu
+```
+Executing the above `TaskRun` will result in an error that looks like:
+
+```
+Error from server (BadRequest): error when creating "STDIN": admission webhook "validation.webhook.pipeline.tekton.dev" denied the request: validation failed: image cannot be used with Ref: spec.taskSpec.steps[0].image
+```

examples/v1/taskruns/alpha/stepaction.yaml

@@ -0,0 +1,19 @@
+apiVersion: tekton.dev/v1alpha1
+kind: StepAction
+metadata:
+  name: step-action
+spec:
+  image: alpine
+  script: |
+    echo "I am a Step Action!!!"
+---
+apiVersion: tekton.dev/v1
+kind: TaskRun
+metadata:
+  name: step-action-run
+spec:
+  TaskSpec:
+    steps:
+      - name: action-runner
+        ref:
+          name: step-action

pkg/reconciler/taskrun/resources/taskref.go

@@ -123,6 +123,15 @@ func GetTaskFunc(ctx context.Context, k8s kubernetes.Interface, tekton clientset
 	}
 }
 
+// GetStepActionFunc is a factory function that will use the given Ref as context to return a valid GetStepAction function.
+func GetStepActionFunc(tekton clientset.Interface, namespace string) GetStepAction {
+	local := &LocalRefResolver{
+		Namespace:    namespace,
+		Tektonclient: tekton,
+	}
+	return local.GetStepAction
+}
+
 // resolveTask accepts an impl of remote.Resolver and attempts to
 // fetch a task with given name and verify the v1beta1 task if trusted resources is enabled.
 // An error is returned if the remoteresource doesn't work
@@ -222,6 +231,26 @@ func (l *LocalTaskRefResolver) GetTask(ctx context.Context, name string) (*v1.Ta
 	return task, nil, nil, nil
 }
 
+// LocalRefResolver uses the current cluster to resolve a stepaction reference.
+type LocalRefResolver struct {
+	Namespace    string
+	Tektonclient clientset.Interface
+}
+
+// GetStepAction will resolve a StepAction from the local cluster using a versioned Tekton client.
+// It will return an error if it can't find an appropriate StepAction for any reason.
+func (l *LocalRefResolver) GetStepAction(ctx context.Context, name string) (*v1alpha1.StepAction, *v1.RefSource, error) {
+	// If we are going to resolve this reference locally, we need a namespace scope.
+	if l.Namespace == "" {
+		return nil, nil, fmt.Errorf("must specify namespace to resolve reference to step action %s", name)
+	}
+	stepAction, err := l.Tektonclient.TektonV1alpha1().StepActions(l.Namespace).Get(ctx, name, metav1.GetOptions{})
+	if err != nil {
+		return nil, nil, err
+	}
+	return stepAction, nil, nil
+}
+
 // IsGetTaskErrTransient returns true if an error returned by GetTask is retryable.
 func IsGetTaskErrTransient(err error) bool {
 	return strings.Contains(err.Error(), errEtcdLeaderChange)

pkg/reconciler/taskrun/resources/taskref_test.go

@@ -51,6 +51,19 @@ import (
 )
 
 var (
+	simpleNamespacedStepAction = &v1alpha1.StepAction{
+		ObjectMeta: metav1.ObjectMeta{
+			Name:      "simple",
+			Namespace: "default",
+		},
+		TypeMeta: metav1.TypeMeta{
+			APIVersion: "tekton.dev/v1alpha1",
+			Kind:       "StepAction",
+		},
+		Spec: v1alpha1.StepActionSpec{
+			Image: "something",
+		},
+	}
 	simpleNamespacedTask = &v1.Task{
 		ObjectMeta: metav1.ObjectMeta{
 			Name:      "simple",
@@ -296,6 +309,104 @@ func TestLocalTaskRef(t *testing.T) {
 	}
 }
 
+func TestLocalRef(t *testing.T) {
+	testcases := []struct {
+		name        string
+		namespace   string
+		stepactions []runtime.Object
+		ref         *v1.Ref
+		expected    runtime.Object
+		wantErr     error
+	}{
+		{
+			name:      "local-step-action",
+			namespace: "default",
+			stepactions: []runtime.Object{
+				&v1alpha1.StepAction{
+					ObjectMeta: metav1.ObjectMeta{
+						Name:      "simple",
+						Namespace: "default",
+					},
+				},
+				&v1alpha1.StepAction{
+					ObjectMeta: metav1.ObjectMeta{
+						Name:      "dummy",
+						Namespace: "default",
+					},
+				},
+			},
+			ref: &v1.Ref{
+				Name: "simple",
+			},
+			expected: &v1alpha1.StepAction{
+				ObjectMeta: metav1.ObjectMeta{
+					Name:      "simple",
+					Namespace: "default",
+				},
+			},
+			wantErr: nil,
+		}, {
+			name:        "step-action-not-found",
+			namespace:   "default",
+			stepactions: []runtime.Object{},
+			ref: &v1.Ref{
+				Name: "simple",
+			},
+			expected: nil,
+			wantErr:  errors.New(`stepactions.tekton.dev "simple" not found`),
+		}, {
+			name:      "local-step-action-missing-namespace",
+			namespace: "",
+			stepactions: []runtime.Object{
+				&v1alpha1.StepAction{
+					ObjectMeta: metav1.ObjectMeta{
+						Name:      "simple",
+						Namespace: "default",
+					},
+				},
+			},
+			ref: &v1.Ref{
+				Name: "simple",
+			},
+			wantErr: fmt.Errorf("must specify namespace to resolve reference to step action simple"),
+		},
+	}
+
+	for _, tc := range testcases {
+		t.Run(tc.name, func(t *testing.T) {
+			ctx := context.Background()
+			ctx, cancel := context.WithCancel(ctx)
+			defer cancel()
+			tektonclient := fake.NewSimpleClientset(tc.stepactions...)
+
+			lc := &resources.LocalRefResolver{
+				Namespace:    tc.namespace,
+				Tektonclient: tektonclient,
+			}
+
+			task, refSource, err := lc.GetStepAction(ctx, tc.ref.Name)
+			if tc.wantErr != nil {
+				if err == nil {
+					t.Fatal("Expected error but found nil instead")
+				}
+				if tc.wantErr.Error() != err.Error() {
+					t.Fatalf("Received different error ( %#v )", err)
+				}
+			} else if tc.wantErr == nil && err != nil {
+				t.Fatalf("Received unexpected error ( %#v )", err)
+			}
+
+			if d := cmp.Diff(tc.expected, task); tc.expected != nil && d != "" {
+				t.Error(diff.PrintWantGot(d))
+			}
+
+			// local cluster step actions have empty source for now. This may be changed in future.
+			if refSource != nil {
+				t.Errorf("expected refsource is nil, but got %v", refSource)
+			}
+		})
+	}
+}
 func TestGetTaskFunc_Local(t *testing.T) {
 	ctx := context.Background()
 
@@ -405,6 +516,47 @@ func TestGetTaskFunc_Local(t *testing.T) {
 	}
 }
 
+func TestGetStepActionFunc_Local(t *testing.T) {
+	ctx := context.Background()
+
+	testcases := []struct {
+		name             string
+		localStepActions []runtime.Object
+		ref              *v1.Ref
+		expected         runtime.Object
+	}{
+		{
+			name:             "local-step-action",
+			localStepActions: []runtime.Object{simpleNamespacedStepAction},
+			ref: &v1.Ref{
+				Name: "simple",
+			},
+			expected: simpleNamespacedStepAction,
+		},
+	}
+
+	for _, tc := range testcases {
+		t.Run(tc.name, func(t *testing.T) {
+			tektonclient := fake.NewSimpleClientset(tc.localStepActions...)
+
+			fn := resources.GetStepActionFunc(tektonclient, "default")
+
+			stepAction, refSource, err := fn(ctx, tc.ref.Name)
+			if err != nil {
+				t.Fatalf("failed to call stepActionfn: %s", err.Error())
+			}
+
+			if diff := cmp.Diff(stepAction, tc.expected); tc.expected != nil && diff != "" {
+				t.Error(diff)
+			}
+
+			// local cluster task has empty RefSource for now. This may be changed in future.
+			if refSource != nil {
+				t.Errorf("expected refSource is nil, but got %v", refSource)
+			}
+		})
+	}
+}
 func TestGetTaskFuncFromTaskRunSpecAlreadyFetched(t *testing.T) {
 	ctx := context.Background()
 	ctx, cancel := context.WithCancel(ctx)