Add a new method to the PipelineResource interface for customization …

…of the Output directory

We previously initialized each Output Resource with an empty directory. This changes the
behavior to initialize this with a custom set of files per resource. The behavior now is
the same as before, with each resource embedding a helper to create empty directories.

Over time we can customize this where necessary.

pkg/apis/pipeline/v1alpha1/build_gcs_resource.go

@@ -70,6 +70,9 @@ type BuildGCSResource struct {
 	Type         PipelineResourceType
 	Location     string
 	ArtifactType GCSArtifactType
+
+	// Initialize an empty output directory
+	EmptyDirOutputResource
 }
 
 // NewBuildGCSResource creates a new BuildGCS resource to pass to a Task

pkg/apis/pipeline/v1alpha1/cloud_event_resource.go

@@ -31,6 +31,8 @@ type CloudEventResource struct {
 	Type PipelineResourceType `json:"type"`
 	// TargetURI is the URI of the sink which the cloud event is develired to
 	TargetURI string `json:"targetURI"`
+	// Initialize an empty output directory
+	EmptyDirOutputResource
 }
 
 // NewCloudEventResource creates a new CloudEvent resource to pass to a Task

pkg/apis/pipeline/v1alpha1/cluster_resource.go

@@ -54,6 +54,9 @@ type ClusterResource struct {
 	CAData []byte `json:"cadata"`
 	//Secrets holds a struct to indicate a field name and corresponding secret name to populate it
 	Secrets []SecretParam `json:"secrets"`
+
+	// Initialize an empty output directory
+	EmptyDirOutputResource
 }
 
 // NewClusterResource create a new k8s cluster resource to pass to a pipeline task

pkg/apis/pipeline/v1alpha1/gcs_resource.go

@@ -41,6 +41,9 @@ type GCSResource struct {
 	TypeDir  bool                 `json:"typeDir"`
 	//Secret holds a struct to indicate a field name and corresponding secret name to populate it
 	Secrets []SecretParam `json:"secrets"`
+
+	// Initialize an empty output directory
+	EmptyDirOutputResource
 }
 
 // NewGCSResource creates a new GCS resource to pass to a Task

pkg/apis/pipeline/v1alpha1/git_resource.go

@@ -44,6 +44,9 @@ type GitResource struct {
 	// https://git-scm.com/docs/gitrevisions#_specifying_revisions for more
 	// information.
 	Revision string `json:"revision"`
+
+	// Initialize an empty output directory
+	EmptyDirOutputResource
 }
 
 // NewGitResource creates a new git resource to pass to a Task

pkg/apis/pipeline/v1alpha1/image_resource.go

@@ -53,6 +53,9 @@ type ImageResource struct {
 	URL            string               `json:"url"`
 	Digest         string               `json:"digest"`
 	OutputImageDir string
+
+	// Initialize an empty output directory
+	EmptyDirOutputResource
 }
 
 // GetName returns the name of the resource

pkg/apis/pipeline/v1alpha1/pull_request_resource.go

@@ -47,6 +47,9 @@ type PullRequestResource struct {
 	URL string `json:"url"`
 	// Secrets holds a struct to indicate a field name and corresponding secret name to populate it.
 	Secrets []SecretParam `json:"secrets"`
+
+	// Initialize an empty output directory
+	EmptyDirOutputResource
 }
 
 // NewPullRequestResource create a new git resource to pass to a Task

pkg/apis/pipeline/v1alpha1/resource_types.go

@@ -57,6 +57,7 @@ type PipelineResourceInterface interface {
 	GetType() PipelineResourceType
 	Replacements() map[string]string
 	GetDownloadSteps(sourcePath string) ([]Step, error)
+	GetOutputInitializationSteps(name, sourcePath string) []Step
 	GetUploadSteps(sourcePath string) ([]Step, error)
 	GetUploadVolumeSpec(spec *TaskSpec) ([]corev1.Volume, error)
 	GetDownloadVolumeSpec(spec *TaskSpec) ([]corev1.Volume, error)
@@ -152,3 +153,13 @@ func ResourceFromType(r *PipelineResource) (PipelineResourceInterface, error) {
 	}
 	return nil, xerrors.Errorf("%s is an invalid or unimplemented PipelineResource", r.Spec.Type)
 }
+
+// EmptyDirOutputResource is a partial struct that can be embedded into other resources.
+// The behavior is to create an empty output directory.
+type EmptyDirOutputResource struct {
+}
+
+// GetOutputInitializationSteps returns a set of steps to be used to initialize an output directory.
+func (e *EmptyDirOutputResource) GetOutputInitializationSteps(name, sourcePath string) []Step {
+	return []Step{CreateDirStep(name, sourcePath)}
+}

pkg/reconciler/v1alpha1/taskrun/resources/output_resource.go

@@ -123,9 +123,9 @@ func AddOutputResources(
 			resourceVolumes = append(resourceVolumes, as.GetSecretsVolumes()...)
 		}
 
-		// Add containers to mkdir each output directory. This should run before the build steps themselves.
-		mkdirSteps := []v1alpha1.Step{v1alpha1.CreateDirStep(boundResource.Name, sourcePath)}
-		taskSpec.Steps = append(mkdirSteps, taskSpec.Steps...)
+		// Add containers to initialize each output directory. This should run before the build steps themselves.
+		initOutputSteps := resource.GetOutputInitializationSteps(boundResource.Name, sourcePath)
+		taskSpec.Steps = append(initOutputSteps, taskSpec.Steps...)
 		taskSpec.Steps = append(taskSpec.Steps, resourceSteps...)
 		taskSpec.Volumes = append(taskSpec.Volumes, resourceVolumes...)