fix(config): suppress workspace mount when workspaceMount is empty string

pkg/devcontainer/config.go

@@ -192,8 +192,8 @@ func (r *runner) substitute(
 	if parsedConfig.WorkspaceFolder != "" {
 		substitutionContext.ContainerWorkspaceFolder = parsedConfig.WorkspaceFolder
 	}
-	if parsedConfig.WorkspaceMount != "" {
-		substitutionContext.WorkspaceMount = parsedConfig.WorkspaceMount
+	if parsedConfig.WorkspaceMount != nil {
+		substitutionContext.WorkspaceMount = *parsedConfig.WorkspaceMount
 	}
 
 	if options.WorkspaceMountConsistency != "" {

pkg/devcontainer/config/config.go

@@ -219,7 +219,8 @@ type NonComposeBase struct {
 	RunArgs []string `json:"runArgs,omitempty"`
 
 	// The --mount parameter for docker run. The default is to mount the project folder at /workspaces/$project.
-	WorkspaceMount string `json:"workspaceMount,omitempty"`
+	// Per the devcontainer spec, empty string suppresses the default workspace mount.
+	WorkspaceMount *string `json:"workspaceMount,omitempty"`
 }
 
 type DockerfileContainer struct {

pkg/devcontainer/config/extends.go

@@ -185,7 +185,7 @@ func mergeContainerScalars(result, child *DevContainerConfig) {
 	if child.WorkspaceFolder != "" {
 		result.WorkspaceFolder = child.WorkspaceFolder
 	}
-	if child.WorkspaceMount != "" {
+	if child.WorkspaceMount != nil {
 		result.WorkspaceMount = child.WorkspaceMount
 	}
 	if child.ShutdownAction != "" {

pkg/devcontainer/config/result.go

@@ -26,8 +26,11 @@ type DevContainerConfigWithPath struct {
 }
 
 func GetMounts(result *Result) []*Mount {
-	workspaceMount := ParseMount(result.SubstitutionContext.WorkspaceMount)
-	mounts := []*Mount{&workspaceMount}
+	var mounts []*Mount
+	if result.SubstitutionContext.WorkspaceMount != "" {
+		workspaceMount := ParseMount(result.SubstitutionContext.WorkspaceMount)
+		mounts = append(mounts, &workspaceMount)
+	}
 	for _, m := range result.MergedConfig.Mounts {
 		if m.Type == "bind" {
 			mounts = append(mounts, m)

pkg/devcontainer/config_test.go

@@ -267,7 +267,7 @@ func (s *SubstituteTestSuite) TestSubstitute_WorkspaceMountConsistencyReplacesEx
 	rawConfig := &config.DevContainerConfig{
 		ImageContainer: config.ImageContainer{Image: "alpine:latest"},
 		NonComposeBase: config.NonComposeBase{
-			WorkspaceMount: "type=bind,source=/src,target=/ws,consistency='consistent'",
+			WorkspaceMount: ptr("type=bind,source=/src,target=/ws,consistency='consistent'"),
 		},
 	}
 	options := provider2.CLIOptions{

pkg/devcontainer/run.go

@@ -350,9 +350,18 @@ func getWorkspace(
 	workspaceFolder, workspaceID string,
 	conf *config.DevContainerConfig,
 ) (string, string) {
-	if conf.WorkspaceMount != "" {
-		mount := config.ParseMount(conf.WorkspaceMount)
-		ws := conf.WorkspaceMount
+	if conf.WorkspaceMount != nil {
+		// Explicit empty string means suppress the workspace mount entirely.
+		if *conf.WorkspaceMount == "" {
+			containerMountFolder := conf.WorkspaceFolder
+			if containerMountFolder == "" {
+				containerMountFolder = "/workspaces/" + workspaceID
+			}
+			return "", containerMountFolder
+		}
+
+		mount := config.ParseMount(*conf.WorkspaceMount)
+		ws := *conf.WorkspaceMount
 		if needsDefaultConsistency() && !mountHasConsistency(ws) {
 			ws += ",consistency='consistent'"
 		}

pkg/devcontainer/run_test.go

@@ -131,11 +131,13 @@ func searchString(s, substr string) bool {
 	return false
 }
 
+func strPtr(s string) *string { return &s }
+
 func TestGetWorkspace_CustomWorkspaceMount(t *testing.T) {
 	customMount := "type=bind,source=/host/src,target=/custom-ws"
 	conf := &config.DevContainerConfig{
 		NonComposeBase: config.NonComposeBase{
-			WorkspaceMount: customMount,
+			WorkspaceMount: strPtr(customMount),
 		},
 	}
 
@@ -185,25 +187,38 @@ func TestGetWorkspace_DefaultMountWithWorkspaceFolder(t *testing.T) {
 func TestGetWorkspace_EmptyWorkspaceMount(t *testing.T) {
 	conf := &config.DevContainerConfig{
 		NonComposeBase: config.NonComposeBase{
-			WorkspaceMount: "",
+			WorkspaceMount: strPtr(""),
 		},
 	}
 
 	mount, folder := getWorkspace("/home/user/project", "ws-id", conf)
 
+	if mount != "" {
+		t.Fatalf("expected empty mount string (suppressed), got %q", mount)
+	}
 	if folder != "/workspaces/ws-id" {
 		t.Fatalf("expected default folder, got %q", folder)
 	}
+}
+
+func TestGetWorkspace_NilWorkspaceMount(t *testing.T) {
+	conf := &config.DevContainerConfig{}
+
+	mount, folder := getWorkspace("/home/user/project", "ws-id", conf)
+
 	if !contains(mount, "type=bind") {
-		t.Fatalf("expected default bind mount, got %q", mount)
+		t.Fatalf("expected default bind mount for nil WorkspaceMount, got %q", mount)
+	}
+	if folder != "/workspaces/ws-id" {
+		t.Fatalf("expected default folder, got %q", folder)
 	}
 }
 
 func TestGetWorkspace_UserConsistencyPreserved(t *testing.T) {
 	customMount := "type=bind,source=/src,target=/ws,consistency=delegated"
 	conf := &config.DevContainerConfig{
 		NonComposeBase: config.NonComposeBase{
-			WorkspaceMount: customMount,
+			WorkspaceMount: strPtr(customMount),
 		},
 	}
 

pkg/devcontainer/single.go

@@ -428,8 +428,12 @@ func (r *runner) getDockerlessRunOptions(
 	substitutionContext *config.SubstitutionContext,
 	buildInfo *config.BuildInfo,
 ) (*driver.RunOptions, error) {
-	// parse workspace mount
-	workspaceMountParsed := config.ParseMount(substitutionContext.WorkspaceMount)
+	// parse workspace mount — nil when suppressed via workspaceMount: ""
+	var workspaceMountPtr *config.Mount
+	if substitutionContext.WorkspaceMount != "" {
+		parsed := config.ParseMount(substitutionContext.WorkspaceMount)
+		workspaceMountPtr = &parsed
+	}
 
 	// add metadata as label here
 	marshalled, err := metadata.MarshalImageMetadata(buildInfo.ImageMetadata.Raw)
@@ -496,7 +500,7 @@ func (r *runner) getDockerlessRunOptions(
 		},
 		Privileged:     mergedConfig.Privileged,
 		Init:           mergedConfig.Init,
-		WorkspaceMount: &workspaceMountParsed,
+		WorkspaceMount: workspaceMountPtr,
 		Mounts:         mounts,
 		Userns:         substitutionContext.Userns,
 		UidMap:         substitutionContext.UidMap,
@@ -509,8 +513,12 @@ func (r *runner) getRunOptions(
 	substitutionContext *config.SubstitutionContext,
 	buildInfo *config.BuildInfo,
 ) (*driver.RunOptions, error) {
-	// parse workspace mount
-	workspaceMountParsed := config.ParseMount(substitutionContext.WorkspaceMount)
+	// parse workspace mount — nil when suppressed via workspaceMount: ""
+	var workspaceMountPtr *config.Mount
+	if substitutionContext.WorkspaceMount != "" {
+		parsed := config.ParseMount(substitutionContext.WorkspaceMount)
+		workspaceMountPtr = &parsed
+	}
 
 	// add metadata as label here
 	marshalled, err := metadata.MarshalImageMetadata(buildInfo.ImageMetadata.Raw)
@@ -553,7 +561,7 @@ func (r *runner) getRunOptions(
 		Labels:         labels,
 		Privileged:     mergedConfig.Privileged,
 		Init:           mergedConfig.Init,
-		WorkspaceMount: &workspaceMountParsed,
+		WorkspaceMount: workspaceMountPtr,
 		SecurityOpt:    mergedConfig.SecurityOpt,
 		Mounts:         mergedConfig.Mounts,
 		Userns:         substitutionContext.Userns,

pkg/driver/kubernetes/run.go

@@ -104,6 +104,11 @@ func (k *KubernetesDriver) runContainer(
 ) (err error) {
 	// get workspace mount
 	mount := options.WorkspaceMount
+	if mount == nil {
+		return fmt.Errorf(
+			"workspace mount is suppressed; cannot run in Kubernetes without a workspace mount",
+		)
+	}
 	if mount.Target == "" {
 		return fmt.Errorf("workspace mount target is empty")
 	}