feat(cmd): better ergonomics around lk app and templates

cmd/lk/app.go

@@ -94,12 +94,32 @@ var (
 					Action:    runTask,
 				},
 				{
-					Hidden: true,
-					Name:   "env",
-					Usage:  "Manage environment variables",
-					Before: requireProject,
+					Name:  "env",
+					Usage: "Print project environment variables expanded from a .env.example file",
+					Flags: []cli.Flag{
+						&cli.BoolFlag{
+							Name:    "w",
+							Aliases: []string{"write"},
+							Usage:   "Write environment variables to .env.local file",
+						},
+					},
+					ArgsUsage: "[DIR] location of the project directory (default: current directory)",
+					Before:    requireProject,
 					Action: func(ctx context.Context, cmd *cli.Command) error {
-						return instantiateEnv(ctx, cmd, ".", nil)
+						rootDir := cmd.Args().First()
+						if rootDir == "" {
+							rootDir = "."
+						}
+
+						env, err := instantiateEnv(ctx, cmd, rootDir, nil)
+						if err != nil {
+							return err
+						}
+						if cmd.Bool("write") {
+							return bootstrap.WriteDotEnv(rootDir, env)
+						} else {
+							return bootstrap.PrintDotEnv(env)
+						}
 					},
 				},
 			},
@@ -254,9 +274,11 @@ func setupTemplate(ctx context.Context, cmd *cli.Command) error {
 
 	fmt.Println("Instantiating environment...")
 	addlEnv := &map[string]string{"LIVEKIT_SANDBOX_ID": sandboxID}
-	if err := instantiateEnv(ctx, cmd, appName, addlEnv); err != nil {
+	env, err := instantiateEnv(ctx, cmd, appName, addlEnv)
+	if err != nil {
 		return err
 	}
+	bootstrap.WriteDotEnv(appName, env)
 
 	if install {
 		fmt.Println("Installing template...")
@@ -307,7 +329,7 @@ func cleanupTemplate(ctx context.Context, cmd *cli.Command, appName string) erro
 	return bootstrap.CleanupTemplate(appName)
 }
 
-func instantiateEnv(ctx context.Context, cmd *cli.Command, rootPath string, addlEnv *map[string]string) error {
+func instantiateEnv(ctx context.Context, cmd *cli.Command, rootPath string, addlEnv *map[string]string) (map[string]string, error) {
 	env := map[string]string{
 		"LIVEKIT_API_KEY":    project.APIKey,
 		"LIVEKIT_API_SECRET": project.APISecret,
@@ -350,6 +372,9 @@ func doPostCreate(ctx context.Context, _ *cli.Command, rootPath string, verbose
 	if err != nil {
 		return err
 	}
+	if tf == nil {
+		return nil
+	}
 
 	task, err := bootstrap.NewTask(ctx, tf, rootPath, string(bootstrap.TaskPostCreate), verbose)
 	if task == nil || err != nil {

pkg/bootstrap/bootstrap.go

@@ -21,13 +21,13 @@ import (
 	"context"
 	"encoding/json"
 	"errors"
+	"fmt"
 	"io"
 	"io/fs"
 	"net/http"
 	"os"
 	"os/exec"
 	"path"
-	"path/filepath"
 	"runtime"
 	"strings"
 
@@ -122,7 +122,14 @@ func FetchSandboxDetails(ctx context.Context, sid, token, serverURL string) (*Sa
 }
 
 func ParseTaskfile(rootPath string) (*ast.Taskfile, error) {
-	file, err := os.ReadFile(path.Join(rootPath, TaskFile))
+	taskfilePath := path.Join(rootPath, TaskFile)
+
+	// taskfile.yaml is optional
+	if _, err := os.Stat(taskfilePath); err != nil && errors.Is(err, fs.ErrNotExist) {
+		return nil, nil
+	}
+
+	file, err := os.ReadFile(taskfilePath)
 	if err != nil {
 		return nil, err
 	}
@@ -180,54 +187,62 @@ func NewTask(ctx context.Context, tf *ast.Taskfile, dir, taskName string, verbos
 
 type PromptFunc func(key string, value string) (string, error)
 
-// Recursively walk the repo, reading in any .env.example file if present in
-// that directory, replacing all `substitutions`, prompting for others, and
-// writing to .env.local in that directory.
-func InstantiateDotEnv(ctx context.Context, rootDir string, substitutions map[string]string, verbose bool, prompt PromptFunc) error {
+// Read .env.example file if present in rootDir, replacing all `substitutions`,
+// prompting for others, and returning the result as a map.
+func InstantiateDotEnv(ctx context.Context, rootDir string, substitutions map[string]string, verbose bool, prompt PromptFunc) (map[string]string, error) {
 	promptedVars := map[string]string{}
 
-	return filepath.WalkDir(rootDir, func(filePath string, d fs.DirEntry, err error) error {
-		if err != nil {
-			return err
-		}
-
-		if d.Name() == EnvExampleFile {
-			envMap, err := godotenv.Read(filePath)
-			if err != nil {
-				return err
-			}
+	envExamplePath := path.Join(rootDir, EnvExampleFile)
+	stat, err := os.Stat(envExamplePath)
+	if err != nil {
+		return nil, err
+	}
+	if stat.IsDir() {
+		return nil, errors.New("env.example file is a directory")
+	}
 
-			for key, oldValue := range envMap {
-				// if key is a substitution, replace it
-				if value, ok := substitutions[key]; ok {
-					envMap[key] = value
-					// if key was already promped, use that value
-				} else if alreadyPromptedValue, ok := promptedVars[key]; ok {
-					envMap[key] = alreadyPromptedValue
-				} else {
-					// prompt for value
-					newValue, err := prompt(key, oldValue)
-					if err != nil {
-						return err
-					}
-					envMap[key] = newValue
-					promptedVars[key] = newValue
-				}
-			}
+	envMap, err := godotenv.Read(envExamplePath)
+	if err != nil {
+		return nil, err
+	}
 
-			envContents, err := godotenv.Marshal(envMap)
+	for key, oldValue := range envMap {
+		// if key is a substitution, replace it
+		if value, ok := substitutions[key]; ok {
+			envMap[key] = value
+			// if key was already promped, use that value
+		} else if alreadyPromptedValue, ok := promptedVars[key]; ok {
+			envMap[key] = alreadyPromptedValue
+		} else {
+			// prompt for value
+			newValue, err := prompt(key, oldValue)
 			if err != nil {
-				return err
-			}
-
-			envLocalPath := path.Join(path.Dir(filePath), EnvLocalFile)
-			if err := os.WriteFile(envLocalPath, []byte(envContents), 0700); err != nil {
-				return err
+				return nil, err
 			}
+			envMap[key] = newValue
+			promptedVars[key] = newValue
 		}
+	}
+
+	return envMap, nil
+}
 
-		return nil
-	})
+func PrintDotEnv(envMap map[string]string) error {
+	envContents, err := godotenv.Marshal(envMap)
+	if err != nil {
+		return err
+	}
+	_, err = fmt.Println(envContents)
+	return err
+}
+
+func WriteDotEnv(rootDir string, envMap map[string]string) error {
+	envContents, err := godotenv.Marshal(envMap)
+	if err != nil {
+		return err
+	}
+	envLocalPath := path.Join(rootDir, EnvLocalFile)
+	return os.WriteFile(envLocalPath, []byte(envContents), 0700)
 }
 
 func CloneTemplate(url, dir string) (string, string, error) {