Initialize working dirs inside workspace dir

In order to allow steps to define workingDirs that are subdirectories of the workspace directory we need to make sure they have been created first since they will not exist on startup.

Fixes tektoncd#725

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

@@ -93,9 +93,14 @@ const (
 	unnamedInitContainerPrefix = "build-step-unnamed-"
 	// Name of the credential initialization container.
 	credsInit = "credential-initializer"
+	// Name of the working dir initialization container.
+	workingDirInit = "working-dir-initializer"
 )
 
 var (
+	// The container used to initialize working directories before the build runs.
+	bashWorkingDirImage = flag.String("bash-working-dir-image", "override-with-bash-noop:latest",
+		"The container image for preparing our Build's working directories.")
 	// The container used to initialize credentials before the build runs.
 	credsImage = flag.String("creds-image", "override-with-creds:latest",
 		"The container image for preparing our Build's credentials.")
@@ -162,6 +167,45 @@ func makeCredentialInitializer(serviceAccountName, namespace string, kubeclient
 	}, volumes, nil
 }
 
+func makeWorkingDirScript(workingDirs map[string]bool) string {
+	script := ""
+	for wd := range workingDirs {
+		if wd != "" {
+			p := filepath.Clean(wd)
+			if rel, err := filepath.Rel(workspaceDir, p); err == nil && !strings.HasPrefix(rel, ".") {
+				if script == "" {
+					script = fmt.Sprintf("mkdir -p %s", p)
+				} else {
+					script = fmt.Sprintf("%s %s", script, p)
+				}
+			}
+		}
+	}
+
+	return script
+}
+
+func makeWorkingDirInitializer(steps []corev1.Container) *corev1.Container {
+	workingDirs := make(map[string]bool)
+	for _, step := range steps {
+		workingDirs[step.WorkingDir] = true
+	}
+
+	if script := makeWorkingDirScript(workingDirs); script != "" {
+		return &corev1.Container{
+			Name:         names.SimpleNameGenerator.RestrictLengthWithRandomSuffix(containerPrefix + workingDirInit),
+			Image:        *bashWorkingDirImage,
+			Command:      []string{"/ko-app/bash"},
+			Args:         []string{"-args", script},
+			VolumeMounts: implicitVolumeMounts,
+			Env:          implicitEnvVars,
+			WorkingDir:   workspaceDir,
+		}
+	}
+
+	return nil
+}
+
 // GetPod returns the Pod for the given pod name
 type GetPod func(string, metav1.GetOptions) (*corev1.Pod, error)
 
@@ -197,6 +241,10 @@ func MakePod(taskRun *v1alpha1.TaskRun, taskSpec v1alpha1.TaskSpec, kubeclient k
 	initContainers := []corev1.Container{*cred}
 	podContainers := []corev1.Container{}
 
+	if workingDir := makeWorkingDirInitializer(taskSpec.Steps); workingDir != nil {
+		initContainers = append(initContainers, *workingDir)
+	}
+
 	maxIndicesByResource := findMaxResourceRequest(taskSpec.Steps, corev1.ResourceCPU, corev1.ResourceMemory, corev1.ResourceEphemeralStorage)
 
 	for i := range taskSpec.Steps {

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

@@ -19,6 +19,7 @@ package resources
 import (
 	"crypto/rand"
 	"fmt"
+	"path/filepath"
 	"strings"
 	"testing"
 
@@ -314,6 +315,52 @@ func TestMakePod(t *testing.T) {
 			},
 			Volumes: implicitVolumes,
 		},
+	}, {
+		desc: "working-dir-in-workspace-dir",
+		ts: v1alpha1.TaskSpec{
+			Steps: []corev1.Container{{
+				Name:       "name",
+				Image:      "image",
+				WorkingDir: filepath.Join(workspaceDir, "test"),
+			}},
+		},
+		want: &corev1.PodSpec{
+			RestartPolicy: corev1.RestartPolicyNever,
+			InitContainers: []corev1.Container{{
+				Name:         containerPrefix + credsInit + "-9l9zj",
+				Image:        *credsImage,
+				Command:      []string{"/ko-app/creds-init"},
+				Args:         []string{},
+				Env:          implicitEnvVars,
+				VolumeMounts: implicitVolumeMounts,
+				WorkingDir:   workspaceDir,
+			}, {
+				Name:         containerPrefix + workingDirInit + "-mz4c7",
+				Image:        *bashWorkingDirImage,
+				Command:      []string{"/ko-app/bash"},
+				Args:         []string{"-args", fmt.Sprintf("mkdir -p %s", filepath.Join(workspaceDir, "test"))},
+				Env:          implicitEnvVars,
+				VolumeMounts: implicitVolumeMounts,
+				WorkingDir:   workspaceDir,
+			}},
+			Containers: []corev1.Container{{
+				Name:         "build-step-name",
+				Image:        "image",
+				Env:          implicitEnvVars,
+				VolumeMounts: implicitVolumeMounts,
+				WorkingDir:   filepath.Join(workspaceDir, "test"),
+				Resources: corev1.ResourceRequirements{
+					Requests: corev1.ResourceList{
+						corev1.ResourceCPU:              resource.MustParse("0"),
+						corev1.ResourceMemory:           resource.MustParse("0"),
+						corev1.ResourceEphemeralStorage: resource.MustParse("0"),
+					},
+				},
+			},
+				nopContainer,
+			},
+			Volumes: implicitVolumes,
+		},
 	}} {
 		t.Run(c.desc, func(t *testing.T) {
 			names.TestingSeed()
@@ -374,3 +421,29 @@ func TestMakePod(t *testing.T) {
 		})
 	}
 }
+
+func TestMakeWorkingDirScript(t *testing.T) {
+	for _, c := range []struct {
+		desc        string
+		workingDirs map[string]bool
+		want        string
+	}{{
+		desc:        "default",
+		workingDirs: map[string]bool{"/workspace": true},
+		want:        "",
+	}, {
+		desc:        "simple",
+		workingDirs: map[string]bool{"/workspace/foo": true, "/workspace/bar": true, "/baz": true},
+		want:        "mkdir -p /workspace/foo /workspace/bar",
+	}, {
+		desc:        "empty",
+		workingDirs: map[string]bool{"/workspace": true, "": true, "/baz": true, "/workspacedir": true},
+		want:        "",
+	}} {
+		t.Run(c.desc, func(t *testing.T) {
+			if script := makeWorkingDirScript(c.workingDirs); script != c.want {
+				t.Errorf("Expected `%v`, got `%v`", c.want, script)
+			}
+		})
+	}
+}