Select default emulator on first run #217

carole-lavillonniere · 2026-05-05T08:29:37Z

nit: these tests seem to be a good fit for table-driven tests, WDYT?

great observation, done: abc89ac

-Original file line number
+Diff line change
@@ Expand Up / @@ -30,11 +30,12 @@ import ( @@
     )
     func NewRootCmd(cfg *env.Env, tel *telemetry.Client, logger log.Logger) *cobra.Command {
+    	var firstRun bool
     	root := &cobra.Command{
     		Use:     "lstk",
     		Short:   "LocalStack CLI",
     		Long:    "lstk is the command-line interface for LocalStack.",
-    		PreRunE: initConfig,
+    		PreRunE: initConfigCapturingFirstRun(&firstRun),
     		RunE: func(cmd *cobra.Command, args []string) error {
     			rt, err := runtime.NewDockerRuntime(cfg.DockerHost)
     			if err != nil {
@@ Expand All @@
     			if err != nil {
     				return err
     			}
-    			return startEmulator(cmd.Context(), rt, cfg, tel, logger, persist)
+    			return startEmulator(cmd.Context(), rt, cfg, tel, logger, persist, firstRun)
     		},
     	}
@@ Expand Down Expand Up @@
     	}
     }
-    func startEmulator(ctx context.Context, rt runtime.Runtime, cfg *env.Env, tel *telemetry.Client, logger log.Logger, persist bool) error {
+    func startEmulator(ctx context.Context, rt runtime.Runtime, cfg *env.Env, tel *telemetry.Client, logger log.Logger, persist bool, firstRun bool) error {
     	appConfig, err := config.Get()
     	if err != nil {
     		return fmt.Errorf("failed to get config: %w", err)
@@ Expand All @@
     	}
     	if isInteractiveMode(cfg) {
-    		labelCh := make(chan string, 1)
-    		go func() {
-    			label, ok := container.ResolveEmulatorLabel(ctx, opts.PlatformClient, appConfig.Containers, cfg.AuthToken, logger)
-    			if ok {
-    				config.CachePlanLabel(label)
-    			}
-    			labelCh <- label
-    		}()
     		return ui.Run(ctx, ui.RunOptions{
-    			Runtime:       rt,
-    			Version:       version.Version(),
-    			StartOptions:  opts,
-    			NotifyOptions: notifyOpts,
-    			ConfigPath:    configPath,
-    			EmulatorLabel: config.CachedPlanLabel(),
-    			LabelCh:       labelCh,
+    			Runtime:                rt,
+    			Version:                version.Version(),
+    			StartOptions:           opts,
+    			NotifyOptions:          notifyOpts,
+    			ConfigPath:             configPath,
+    			EmulatorLabel:          config.CachedPlanLabel(),
+    			NeedsEmulatorSelection: firstRun,
     		})
     	}
     	sink := output.NewPlainSink(os.Stdout)
+    	if firstRun && len(appConfig.Containers) > 0 {
+    		emName := appConfig.Containers[0].Type.DisplayName()
+    		sink.Emit(output.MessageEvent{
+    			Severity: output.SeverityNote,
+    			Text:     fmt.Sprintf("Configured with default emulator %s.", emName),
+    		})
+    	}
     	update.NotifyUpdate(ctx, sink, update.NotifyOptions{GitHubToken: cfg.GitHubToken})
     	return container.Start(ctx, rt, sink, opts, false)
     }
@@ Expand Down Expand Up / @@ -296,5 +294,20 @@ func initConfig(cmd *cobra.Command, _ []string) error { @@
     	if path != "" {
     		return config.InitFromPath(path)
     	}
-    	return config.Init()
+    	_, err = config.Init()
+    	return err
+    }
+    func initConfigCapturingFirstRun(firstRun *bool) func(*cobra.Command, []string) error {
+    	return func(cmd *cobra.Command, _ []string) error {
+    		path, err := cmd.Flags().GetString("config")
+    		if err != nil {
+    			return err
+    		}
+    		if path != "" {
+    			return config.InitFromPath(path)
+    		}
+    		*firstRun, err = config.Init()
+    		return err
+    	}
     }

-Original file line number
+Diff line change
@@ Expand Up / @@ -9,21 +9,22 @@ import ( @@
     )
     func newStartCmd(cfg *env.Env, tel *telemetry.Client, logger log.Logger) *cobra.Command {
+    	var firstRun bool
     	cmd := &cobra.Command{
     		Use:     "start",
     		Short:   "Start emulator",
     		Long:    "Start emulator and services.",
-    		PreRunE: initConfig,
-    		RunE: func(cmd *cobra.Command, args []string) error {
+    		PreRunE: initConfigCapturingFirstRun(&firstRun),
+    		RunE: func(c *cobra.Command, args []string) error {
     			rt, err := runtime.NewDockerRuntime(cfg.DockerHost)
     			if err != nil {
     				return err
     			}
-    			persist, err := cmd.Flags().GetBool("persist")
+    			persist, err := c.Flags().GetBool("persist")
     			if err != nil {
     				return err
     			}
-    			return startEmulator(cmd.Context(), rt, cfg, tel, logger, persist)
+    			return startEmulator(c.Context(), rt, cfg, tel, logger, persist, firstRun)
     		},
     	}
     	cmd.Flags().Bool("persist", false, "Enable local persistence (sets LOCALSTACK_PERSISTENCE=1)")
@@ Expand Down @@

-Original file line number
+Diff line change
@@ Expand Up / @@ -52,15 +52,17 @@ func InitFromPath(path string) error { @@
     	return loadConfig(path)
     }
-    func Init() error {
+    // Init loads the config file, searching the standard paths. If no config file
+    // exists, it creates one from the default template and returns firstRun=true.
+    func Init() (firstRun bool, err error) {
     	viper.Reset()
     	setDefaults()
     	viper.SetConfigName(configName)
     	viper.SetConfigType(configType)
     	dirs, err := configSearchDirs()
     	if err != nil {
-    		return err
+    		return false, err
     	}
     	for _, dir := range dirs {
     		viper.AddConfigPath(dir)
@@ Expand All / @@ -70,43 +72,43 @@ func Init() error { @@
     		var notFoundErr viper.ConfigFileNotFoundError
     		if !errors.As(err, &notFoundErr) {
     			if used := viper.ConfigFileUsed(); filepath.Ext(used) == ".yaml" || filepath.Ext(used) == ".yml" {
-    				return fmt.Errorf("%s is from an old lstk version; lstk now uses TOML format — remove it or replace it with a config.toml file", used)
+    				return false, fmt.Errorf("%s is from an old lstk version; lstk now uses TOML format — remove it or replace it with a config.toml file", used)
     			}
-    			return fmt.Errorf("failed to read config file: %w", err)
+    			return false, fmt.Errorf("failed to read config file: %w", err)
     		}
     		// No config found anywhere, create one using creation policy.
     		creationDir, err := configCreationDir()
     		if err != nil {
-    			return err
+    			return false, err
     		}
     		if err := os.MkdirAll(creationDir, 0755); err != nil {
-    			return fmt.Errorf("failed to create config directory: %w", err)
+    			return false, fmt.Errorf("failed to create config directory: %w", err)
     		}
     		configPath := filepath.Join(creationDir, configFileName)
     		f, err := os.OpenFile(configPath, os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0644)
     		if err != nil {
     			if errors.Is(err, os.ErrExist) {
-    				return loadConfig(configPath)
+    				return false, loadConfig(configPath)
     			}
-    			return fmt.Errorf("failed to create config file: %w", err)
+    			return false, fmt.Errorf("failed to create config file: %w", err)
     		}
     		_, writeErr := f.WriteString(defaultConfigTemplate)
     		closeErr := f.Close()
     		if writeErr != nil {
     			_ = os.Remove(configPath)
-    			return fmt.Errorf("failed to write config file: %w", writeErr)
+    			return false, fmt.Errorf("failed to write config file: %w", writeErr)
     		}
     		if closeErr != nil {
     			_ = os.Remove(configPath)
-    			return fmt.Errorf("failed to close config file: %w", closeErr)
+    			return false, fmt.Errorf("failed to close config file: %w", closeErr)
     		}
-    		return loadConfig(configPath)
+    		return true, loadConfig(configPath)
     	}
-    	return nil
+    	return false, nil
     }
     func resolvedConfigPath() string {
@@ Expand Down @@

-Original file line number
+Diff line change
@@ Expand Up / @@ -25,6 +25,12 @@ var emulatorDisplayNames = map[EmulatorType]string{ @@
     	EmulatorAzure:     "Azure",
     }
+    func (e EmulatorType) DisplayName() string {
+    	if name, ok := emulatorDisplayNames[e]; ok {
+    		return name
+    	}
+    	return string(e)
+    }
     var emulatorHealthPaths = map[EmulatorType]string{
     	EmulatorAWS:       "/_localstack/health",
     	EmulatorSnowflake: "/_localstack/health",
@@ Expand Down @@

-Original file line number
+Diff line change
@@ -0,0 +1,34 @@
+    package config
+    import (
+    	"fmt"
+    	"os"
+    	"regexp"
+    )
+    var typeLineRe = regexp.MustCompile(`type\s*=\s*["'](\w+)["']`)
+    // SetEmulatorType rewrites the emulator type in the config file and reloads.
+    // No-op if the requested type is already set.
+    func SetEmulatorType(to EmulatorType) error {
+    	path := resolvedConfigPath()
+    	if path == "" {
+    		return fmt.Errorf("no config file loaded")
+    	}
+    	data, err := os.ReadFile(path)
+    	if err != nil {
+    		return fmt.Errorf("failed to read config file: %w", err)
+    	}
+    	m := typeLineRe.FindStringSubmatch(string(data))
+    	if m == nil {
+    		return fmt.Errorf("no emulator type field found in config")
+    	}
+    	if EmulatorType(m[1]) == to {
+    		return nil
+    	}
+    	updated := typeLineRe.ReplaceAllString(string(data), `type = "`+string(to)+`"`)
+    	if err := os.WriteFile(path, []byte(updated), 0644); err != nil {
+    		return fmt.Errorf("failed to write config file: %w", err)
+    	}
+    	return loadConfig(path)
+    }

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Select default emulator on first run #217

Uh oh!

Diff view

Diff view

There are no files selected for viewing

carole-lavillonniere May 5, 2026

Uh oh!

anisaoshafi May 5, 2026

Uh oh!

Uh oh!

Uh oh!

-Original file line number
+Diff line change
@@ -0,0 +1,61 @@
+    package config
+    import (
+    	"os"
+    	"path/filepath"
+    	"testing"
+    	"github.com/spf13/viper"
+    	"github.com/stretchr/testify/assert"
+    	"github.com/stretchr/testify/require"
+    )
+    func TestSetEmulatorType_WritesAndReloads(t *testing.T) {
+    	dir := t.TempDir()
+    	path := filepath.Join(dir, "config.toml")
+    	require.NoError(t, os.WriteFile(path, []byte("[[containers]]\ntype = \"aws\"\nport = \"4566\"\n"), 0644))
+    	require.NoError(t, loadConfig(path))
+    	t.Cleanup(func() { viper.Reset() })
+    	require.NoError(t, SetEmulatorType(EmulatorSnowflake))
+    	got, err := os.ReadFile(path)
+    	require.NoError(t, err)
+    	assert.Contains(t, string(got), `type = "snowflake"`)
+    	assert.NotContains(t, string(got), `type = "aws"`)
+    	cfg, err := Get()
+    	require.NoError(t, err)
+    	require.Len(t, cfg.Containers, 1)
+    	assert.Equal(t, EmulatorSnowflake, cfg.Containers[0].Type)
+    }
+    func TestSetEmulatorType_NoOpWhenSameEmulator(t *testing.T) {
+    	dir := t.TempDir()
+    	path := filepath.Join(dir, "config.toml")
+    	content := "[[containers]]\ntype = \"aws\"\nport = \"4566\"\n"
+    	require.NoError(t, os.WriteFile(path, []byte(content), 0644))
+    	require.NoError(t, loadConfig(path))
+    	t.Cleanup(func() { viper.Reset() })
+    	require.NoError(t, SetEmulatorType(EmulatorAWS))
+    	got, err := os.ReadFile(path)
+    	require.NoError(t, err)
+    	assert.Equal(t, content, string(got))
+    }
+    func TestSetEmulatorType_PreservesInlineComments(t *testing.T) {
+    	dir := t.TempDir()
+    	path := filepath.Join(dir, "config.toml")
+    	content := "[[containers]]\ntype = \"aws\"     # Emulator type\ntag  = \"latest\"\n"
+    	require.NoError(t, os.WriteFile(path, []byte(content), 0644))
+    	require.NoError(t, loadConfig(path))
+    	t.Cleanup(func() { viper.Reset() })
+    	require.NoError(t, SetEmulatorType(EmulatorSnowflake))
+    	got, err := os.ReadFile(path)
+    	require.NoError(t, err)
+    	assert.Contains(t, string(got), `type = "snowflake"     # Emulator type`)
+    }

Select default emulator on first run #217

Are you sure you want to change the base?

Uh oh!

Select default emulator on first run #217

Uh oh!

Uh oh!

Diff view

Diff view

There are no files selected for viewing

carole-lavillonniere May 5, 2026

Choose a reason for hiding this comment

Uh oh!

anisaoshafi May 5, 2026

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!