Add variable substitution for PVC name

There may be use cases when a Task should initiate a PipelineRun or TaskRun.
It can be beneficial to use the **same PVC** in the PipelineRun or TaskRun
that is initiated, e.g. populated with cached data or a cloned git repository.

When using a workspace with a PersistentVolumeClaim as volume source, the name
of the PVC is known, and can be passed as a _param_ in the PipelineRun or
TaskRun. But when a VolumeClaimTemplate is used as a volume source, the name
is generated. In such use cases, it is useful to be able to "look up" the PVC
name using variable substitution.

Fixes #2505

docs/variables.md

@@ -25,6 +25,7 @@ in `Tasks` and `Pipelines`.
 | `resources.outputs.<resource name>.path` | The path to the output resource's directory. |
 | `results.<result name>.path` | The path to the file where a Task's result should be written. |
 | `workspaces.<workspace name>.path` | The path to the mounted workspace. |
+| `workspaces.<workspace name>.claim` | The name of the PersistentVolumeClaim used as a volume source for the workspace or empty string if a volume source other than PersistentVolumeClaim was used. |
 | `workspaces.<workspace name>.volume` | The name of the volume populating the workspace. |
 | `credentials.path` | The path to the location of credentials written by the `creds-init` init container. |
 

pkg/reconciler/taskrun/resources/apply.go

@@ -96,8 +96,9 @@ func ApplyResources(spec *v1alpha1.TaskSpec, resolvedResources map[string]v1alph
 	return ApplyReplacements(spec, replacements, map[string][]string{})
 }
 
-// ApplyWorkspaces applies the substitution from paths that the workspaces in w are mounted to and the
-// volumes that wb are realized with in the task spec ts.
+// ApplyWorkspaces applies the substitution from paths that the workspaces in w are mounted to, the
+// volumes that wb are realized with in the task spec ts and the PersistentVolumeClaim names for the
+// workspaces.
 func ApplyWorkspaces(spec *v1alpha1.TaskSpec, w []v1alpha1.WorkspaceDeclaration, wb []v1alpha1.WorkspaceBinding) *v1alpha1.TaskSpec {
 	stringReplacements := map[string]string{}
 
@@ -108,6 +109,13 @@ func ApplyWorkspaces(spec *v1alpha1.TaskSpec, w []v1alpha1.WorkspaceDeclaration,
 	for name, vv := range v {
 		stringReplacements[fmt.Sprintf("workspaces.%s.volume", name)] = vv.Name
 	}
+	for _, w := range wb {
+		if w.PersistentVolumeClaim != nil {
+			stringReplacements[fmt.Sprintf("workspaces.%s.claim", w.Name)] = w.PersistentVolumeClaim.ClaimName
+		} else {
+			stringReplacements[fmt.Sprintf("workspaces.%s.claim", w.Name)] = ""
+		}
+	}
 	return ApplyReplacements(spec, stringReplacements, map[string][]string{})
 }
 

pkg/reconciler/taskrun/resources/apply_test.go

@@ -609,6 +609,12 @@ func TestApplyWorkspaces(t *testing.T) {
 			Env: []corev1.EnvVar{{
 				Name:  "template-var",
 				Value: "$(workspaces.myws.volume)",
+			}, {
+				Name:  "pvc-name",
+				Value: "$(workspaces.myws.claim)",
+			}, {
+				Name:  "non-pvc-name",
+				Value: "$(workspaces.otherws.claim)",
 			}},
 		},
 		Steps: []v1alpha1.Step{{Container: corev1.Container{
@@ -671,6 +677,8 @@ func TestApplyWorkspaces(t *testing.T) {
 	}}
 	want := applyMutation(ts, func(spec *v1alpha1.TaskSpec) {
 		spec.StepTemplate.Env[0].Value = "ws-9l9zj"
+		spec.StepTemplate.Env[1].Value = "foo"
+		spec.StepTemplate.Env[2].Value = ""
 
 		spec.Steps[0].Name = "ws-9l9zj"
 		spec.Steps[0].Image = "ws-mz4c7"