Add variable expansion for params in Projected Volume fields

A [projected volume](https://kubernetes.io/docs/concepts/storage/volumes/#projected)
can mount/project files from `Secrets`, `ConfigMaps` and `ServiceAccountTokens`.

Is is good if the end user can choose the name of `Secrets`, `ConfigMaps` and the audience of `ServiceAccountTokens`.
With this commit, the task author can use `params` for `secret.name`, `configmap.name` and `serviceaccounttoken.audience`
in a Projected Volume.

See examples of use cases in tektoncd#2597

Fixes tektoncd#2597

docs/tasks.md

@@ -545,7 +545,7 @@ The `description` field is an optional field that allows you to add an informati
 
 `Tasks` allow you to substitute variable names for the following entities:
 
-- [Parameters and resources]](#substituting-parameters-and-resources)
+- [Parameters and resources](#substituting-parameters-and-resources)
 - [`Array` parameters](#substituting-array-parameters)
 - [`Workspaces`](#substituting-workspace-paths)
 - [`Volume` names and types](#substituting-volume-names-and-paths)

pkg/reconciler/taskrun/resources/apply.go

@@ -166,6 +166,19 @@ func ApplyReplacements(spec *v1beta1.TaskSpec, stringReplacements map[string]str
 		if v.PersistentVolumeClaim != nil {
 			spec.Volumes[i].PersistentVolumeClaim.ClaimName = substitution.ApplyReplacements(v.PersistentVolumeClaim.ClaimName, stringReplacements)
 		}
+		if v.Projected != nil {
+			for _, s := range spec.Volumes[i].Projected.Sources {
+				if s.ConfigMap != nil {
+					s.ConfigMap.Name = substitution.ApplyReplacements(s.ConfigMap.Name, stringReplacements)
+				}
+				if s.Secret != nil {
+					s.Secret.Name = substitution.ApplyReplacements(s.Secret.Name, stringReplacements)
+				}
+				if s.ServiceAccountToken != nil {
+					s.ServiceAccountToken.Audience = substitution.ApplyReplacements(s.ServiceAccountToken.Audience, stringReplacements)
+				}
+			}
+		}
 	}
 
 	// Apply variable substitution to the sidecar definitions

pkg/reconciler/taskrun/resources/apply_test.go

@@ -159,6 +159,27 @@ var (
 					ClaimName: "$(inputs.params.FOO)",
 				},
 			},
+		}, {
+			Name: "some-projected-volumes",
+			VolumeSource: corev1.VolumeSource{
+				Projected: &corev1.ProjectedVolumeSource{
+					Sources: []corev1.VolumeProjection{{
+						ConfigMap: &corev1.ConfigMapProjection{
+							LocalObjectReference: corev1.LocalObjectReference{
+								Name: "$(inputs.params.FOO)",
+							},
+						},
+						Secret: &corev1.SecretProjection{
+							LocalObjectReference: corev1.LocalObjectReference{
+								Name: "$(inputs.params.FOO)",
+							},
+						},
+						ServiceAccountToken: &corev1.ServiceAccountTokenProjection{
+							Audience: "$(inputs.params.FOO)",
+						},
+					}},
+				},
+			},
 		}},
 		Resources: &v1beta1.TaskResources{
 			Inputs: []v1beta1.TaskResource{{
@@ -515,6 +536,9 @@ func TestApplyParameters(t *testing.T) {
 		spec.Volumes[0].VolumeSource.ConfigMap.LocalObjectReference.Name = "world"
 		spec.Volumes[1].VolumeSource.Secret.SecretName = "world"
 		spec.Volumes[2].VolumeSource.PersistentVolumeClaim.ClaimName = "world"
+		spec.Volumes[3].VolumeSource.Projected.Sources[0].ConfigMap.Name = "world"
+		spec.Volumes[3].VolumeSource.Projected.Sources[0].Secret.Name = "world"
+		spec.Volumes[3].VolumeSource.Projected.Sources[0].ServiceAccountToken.Audience = "world"
 
 		spec.Sidecars[0].Container.Image = "bar"
 		spec.Sidecars[0].Container.Env[0].Value = "world"