Add theme to lets settings

docs/docs/changelog.md

@@ -12,6 +12,7 @@ title: Changelog
 * `[Changed]` Add breathing room between the `USAGE` heading and its usage block in help output.
 * `[Refactoring]` Use Go 1.26 `errors.AsType` for type-safe error unwrapping.
 * `[Testing]` Add golden-file tests for help and error rendering in `internal/cmd`, replacing bats format checks with snapshot comparisons.
+* `[Added]` Add a `theme` user setting with `default`, `ansi`, and `synthwave` themes for lets help and styled error output.
 
 ## [0.0.61](https://github.com/lets-cli/lets/releases/tag/v0.0.61)
 

docs/docs/settings.md

@@ -5,7 +5,7 @@ title: Settings
 
 `lets` settings control the behavior of `lets` itself.
 
-Use settings for things like colored output or update notifications. Do not use this file for project commands or runtime env. Project behavior still belongs in `lets.yaml`.
+Use settings for things like colored output, theming, or update notifications. Do not use this file for project commands or runtime env. Project behavior still belongs in `lets.yaml`.
 
 ## Settings file location
 
@@ -48,6 +48,35 @@ Note:
 - this affects `lets` output itself
 - it does not inject `NO_COLOR` into commands from `lets.yaml`
 
+### `theme`
+
+Choose the theme for `lets` styled help and error output.
+
+Supported values:
+
+- `default`
+- `ansi`
+- `synthwave`
+
+Example:
+
+```yaml
+theme: synthwave
+```
+
+Environment override:
+
+- none
+
+Default:
+
+- `theme: default`
+
+Notes:
+
+- this affects `lets` output itself
+- project commands still control their own colors
+
 ### `upgrade_notify`
 
 Enable or disable background update notifications for interactive sessions.
@@ -69,7 +98,8 @@ Default:
 ## Example
 
 ```yaml
-no_color: true
+no_color: false
+theme: default
 upgrade_notify: false
 ```
 

internal/cli/cli.go

@@ -111,7 +111,7 @@ func Main(version string, buildDate string) int {
 		ctx,
 		rootCmd,
 		fang.WithVersion(rootCmd.Version),
-		fang.WithColorSchemeFunc(theme.DefaultColorScheme),
+		fang.WithColorSchemeFunc(theme.ColorSchemeByName(appSettings.Theme)),
 		fang.WithErrorHandler(cmd.ErrorHandler),
 		fang.WithHelpRenderer(cmd.HelpRenderer),
 	); err != nil {

internal/settings/settings.go

@@ -5,23 +5,27 @@ import (
 	"os"
 
 	"github.com/fatih/color"
+	"github.com/lets-cli/lets/internal/theme"
 	"github.com/lets-cli/lets/internal/util"
 	"gopkg.in/yaml.v3"
 )
 
 type FileSettings struct {
-	NoColor       *bool `yaml:"no_color"`
-	UpgradeNotify *bool `yaml:"upgrade_notify"`
+	NoColor       *bool   `yaml:"no_color"`
+	Theme         *string `yaml:"theme"`
+	UpgradeNotify *bool   `yaml:"upgrade_notify"`
 }
 
 type Settings struct {
 	NoColor       bool
+	Theme         string
 	UpgradeNotify bool
 }
 
 func Default() Settings {
 	return Settings{
 		NoColor:       false,
+		Theme:         theme.DefaultName,
 		UpgradeNotify: true,
 	}
 }
@@ -63,12 +67,26 @@ func LoadFile(path string) (Settings, error) {
 		cfg.NoColor = *fileSettings.NoColor
 	}
 
+	if fileSettings.Theme != nil {
+		cfg.Theme = *fileSettings.Theme
+	}
+
 	if fileSettings.UpgradeNotify != nil {
 		cfg.UpgradeNotify = *fileSettings.UpgradeNotify
 	}
 
 	applyEnvOverrides(&cfg)
 
+	if !theme.ValidName(cfg.Theme) {
+		return Settings{}, fmt.Errorf(
+			"invalid theme %q: must be one of %q, %q, %q",
+			cfg.Theme,
+			theme.DefaultName,
+			theme.ANSIName,
+			theme.SynthwaveName,
+		)
+	}
+
 	return cfg, nil
 }
 

internal/settings/settings_test.go

@@ -39,6 +39,9 @@ func TestLoadFile(t *testing.T) {
 		if cfg.NoColor {
 			t.Fatal("expected no_color default to be false")
 		}
+		if cfg.Theme != "default" {
+			t.Fatalf("expected theme default to be %q, got %q", "default", cfg.Theme)
+		}
 		if !cfg.UpgradeNotify {
 			t.Fatal("expected upgrade_notify default to be true")
 		}
@@ -49,7 +52,7 @@ func TestLoadFile(t *testing.T) {
 		unsetEnv(t, "LETS_CHECK_UPDATE")
 
 		path := filepath.Join(t.TempDir(), "config.yaml")
-		err := os.WriteFile(path, []byte("no_color: true\nupgrade_notify: false\n"), 0o644)
+		err := os.WriteFile(path, []byte("no_color: true\ntheme: synthwave\nupgrade_notify: false\n"), 0o644)
 		if err != nil {
 			t.Fatalf("failed to write settings file: %v", err)
 		}
@@ -62,14 +65,17 @@ func TestLoadFile(t *testing.T) {
 		if !cfg.NoColor {
 			t.Fatal("expected no_color to be true")
 		}
+		if cfg.Theme != "synthwave" {
+			t.Fatalf("expected theme to be %q, got %q", "synthwave", cfg.Theme)
+		}
 		if cfg.UpgradeNotify {
 			t.Fatal("expected upgrade_notify to be false")
 		}
 	})
 
 	t.Run("env overrides file values", func(t *testing.T) {
 		path := filepath.Join(t.TempDir(), "config.yaml")
-		err := os.WriteFile(path, []byte("no_color: false\nupgrade_notify: true\n"), 0o644)
+		err := os.WriteFile(path, []byte("no_color: false\ntheme: ansi\nupgrade_notify: true\n"), 0o644)
 		if err != nil {
 			t.Fatalf("failed to write settings file: %v", err)
 		}
@@ -85,11 +91,30 @@ func TestLoadFile(t *testing.T) {
 		if !cfg.NoColor {
 			t.Fatal("expected NO_COLOR to override settings file")
 		}
+		if cfg.Theme != "ansi" {
+			t.Fatalf("expected theme to remain %q, got %q", "ansi", cfg.Theme)
+		}
 		if cfg.UpgradeNotify {
 			t.Fatal("expected LETS_CHECK_UPDATE to disable notifications")
 		}
 	})
 
+	t.Run("rejects invalid theme", func(t *testing.T) {
+		unsetEnv(t, "NO_COLOR")
+		unsetEnv(t, "LETS_CHECK_UPDATE")
+
+		path := filepath.Join(t.TempDir(), "config.yaml")
+		err := os.WriteFile(path, []byte("theme: vaporwave\n"), 0o644)
+		if err != nil {
+			t.Fatalf("failed to write settings file: %v", err)
+		}
+
+		_, err = LoadFile(path)
+		if err == nil {
+			t.Fatal("expected error")
+		}
+	})
+
 	t.Run("rejects unknown fields", func(t *testing.T) {
 		unsetEnv(t, "NO_COLOR")
 		unsetEnv(t, "LETS_CHECK_UPDATE")
@@ -119,7 +144,7 @@ func TestLoad(t *testing.T) {
 		t.Fatalf("failed to create config dir: %v", err)
 	}
 
-	err = os.WriteFile(configPath, []byte("no_color: true\n"), 0o644)
+	err = os.WriteFile(configPath, []byte("no_color: true\ntheme: ansi\n"), 0o644)
 	if err != nil {
 		t.Fatalf("failed to write settings file: %v", err)
 	}
@@ -132,6 +157,9 @@ func TestLoad(t *testing.T) {
 	if !cfg.NoColor {
 		t.Fatal("expected loaded no_color to be true")
 	}
+	if cfg.Theme != "ansi" {
+		t.Fatalf("expected loaded theme to be %q, got %q", "ansi", cfg.Theme)
+	}
 }
 
 func TestApply(t *testing.T) {

internal/theme/theme.go

@@ -8,6 +8,35 @@ import (
 	"github.com/lets-cli/fang"
 )
 
+// Supported theme names.
+const (
+	DefaultName   = "default"
+	ANSIName      = "ansi"
+	SynthwaveName = "synthwave"
+)
+
+// ValidName reports whether name is a supported theme.
+func ValidName(name string) bool {
+	switch name {
+	case DefaultName, ANSIName, SynthwaveName:
+		return true
+	default:
+		return false
+	}
+}
+
+// ColorSchemeByName resolves a theme name to a Fang color scheme.
+func ColorSchemeByName(name string) fang.ColorSchemeFunc {
+	switch name {
+	case ANSIName:
+		return AnsiColorScheme
+	case SynthwaveName:
+		return SynthwaveColorScheme
+	default:
+		return DefaultColorScheme
+	}
+}
+
 // DefaultColorScheme is the default colorscheme.
 func DefaultColorScheme(c lipgloss.LightDarkFunc) fang.ColorScheme {
 	baseCyan := charmtone.Turtle

internal/theme/theme_test.go

@@ -0,0 +1,38 @@
+package theme
+
+import (
+	"testing"
+
+	"charm.land/lipgloss/v2"
+	"github.com/charmbracelet/x/exp/charmtone"
+)
+
+func TestValidName(t *testing.T) {
+	for _, name := range []string{DefaultName, ANSIName, SynthwaveName} {
+		if !ValidName(name) {
+			t.Fatalf("expected %q to be valid", name)
+		}
+	}
+
+	if ValidName("vaporwave") {
+		t.Fatal("expected unknown theme to be invalid")
+	}
+}
+
+func TestColorSchemeByName(t *testing.T) {
+	if got := ColorSchemeByName(DefaultName)(lipgloss.LightDark(true)).Title; got != charmtone.Ash {
+		t.Fatalf("expected default theme title color %v, got %v", charmtone.Ash, got)
+	}
+
+	if got := ColorSchemeByName(ANSIName)(lipgloss.LightDark(true)).ErrorDetails; got != lipgloss.Red {
+		t.Fatalf("expected ansi theme error details color %v, got %v", lipgloss.Red, got)
+	}
+
+	if got := ColorSchemeByName(SynthwaveName)(lipgloss.LightDark(true)).Title; got != charmtone.Grape {
+		t.Fatalf("expected synthwave theme title color %v, got %v", charmtone.Grape, got)
+	}
+
+	if got := ColorSchemeByName("unknown")(lipgloss.LightDark(true)).Title; got != charmtone.Ash {
+		t.Fatalf("expected unknown theme to fall back to %v, got %v", charmtone.Ash, got)
+	}
+}