feat(config): add configurable startup banner output (#893)

README.md

@@ -221,6 +221,21 @@ air -- -h
 air -c .air.toml -- -h
 ```
 
+### Startup banner
+
+Use `misc.startup_banner` to control what Air prints at startup.
+
+```toml
+[misc]
+# Not set (default): show built-in ASCII banner with version.
+
+# Set to empty string: print nothing.
+startup_banner = ""
+
+# Set to custom text: print this text instead of the built-in banner.
+# startup_banner = "API watcher"
+```
+
 ### Entrypoint
 
 Use `build.entrypoint` to point at the binary generated by `build.cmd` and describe how it should be executed. The value can be either a string (just the executable) or an array of strings. When using an array, the first element is the executable (resolved relative to `root` unless it lacks a path separator, in which case `$PATH` is consulted) and every subsequent element is treated as a default argument. Values from `build.args_bin` and the command line are appended after the inline arguments. The legacy `build.bin` field is deprecated and will be removed in a future release, so prefer the entrypoint form going forward.

air_example.toml

@@ -87,6 +87,8 @@ runner = "green"
 [misc]
 # Delete tmp directory on exit
 clean_on_exit = true
+# Startup banner text. Set to "" to hide the banner.
+# startup_banner = ""
 
 [screen]
 clear_on_rebuild = true

main.go

@@ -8,6 +8,7 @@ import (
 	"os/signal"
 	"runtime"
 	"runtime/debug"
+	"strings"
 	"syscall"
 
 	"github.com/air-verse/air/runner"
@@ -73,9 +74,9 @@ func GetVersionInfo() versionInfo { //revive:disable:unexported-return
 	}
 }
 
-func printSplash() {
+func defaultSplashText() string {
 	versionInfo := GetVersionInfo()
-	fmt.Fprintf(os.Stderr, `
+	return fmt.Sprintf(`
   __    _   ___  
  / /\  | | | |_) 
 /_/--\ |_| |_| \_ %s, built with Go %s
@@ -83,6 +84,49 @@ func printSplash() {
 `, versionInfo.airVersion, versionInfo.goVersion)
 }
 
+func versionLineText() string {
+	versionInfo := GetVersionInfo()
+	return fmt.Sprintf("air %s, built with Go %s\n", versionInfo.airVersion, versionInfo.goVersion)
+}
+
+func startupBannerText(cfg *runner.Config) string {
+	if cfg == nil || cfg.Misc.StartupBanner == nil {
+		return defaultSplashText()
+	}
+	return *cfg.Misc.StartupBanner
+}
+
+func printStartupBanner(cfg *runner.Config, respectSilent bool) {
+	if cfg != nil && respectSilent && cfg.Log.Silent {
+		return
+	}
+	banner := startupBannerText(cfg)
+	if banner == "" {
+		return
+	}
+	fmt.Fprint(os.Stderr, banner)
+	if !strings.HasSuffix(banner, "\n") {
+		fmt.Fprintln(os.Stderr)
+	}
+}
+
+func printVersionOutput(cfg *runner.Config) {
+	if cfg == nil || cfg.Misc.StartupBanner == nil {
+		fmt.Fprint(os.Stderr, defaultSplashText())
+		return
+	}
+
+	banner := *cfg.Misc.StartupBanner
+	if banner != "" {
+		fmt.Fprint(os.Stderr, banner)
+		if !strings.HasSuffix(banner, "\n") {
+			fmt.Fprintln(os.Stderr)
+		}
+	}
+
+	fmt.Fprint(os.Stderr, versionLineText())
+}
+
 func main() {
 	switch colorMode {
 	case "always":
@@ -94,22 +138,25 @@ func main() {
 	default:
 		log.Fatal("unsupported color mode: use always, never, auto")
 	}
+
 	if showVersion {
-		printSplash()
+		cfg, err := runner.InitConfigForDisplay(cfgPath, cmdArgs)
+		if err == nil {
+			printVersionOutput(cfg)
+			return
+		}
+		fmt.Fprint(os.Stderr, defaultSplashText())
 		return
 	}
 	sigs := make(chan os.Signal, 1)
 	signal.Notify(sigs, syscall.SIGINT, syscall.SIGTERM, syscall.SIGHUP)
 
-	var err error
 	cfg, err := runner.InitConfig(cfgPath, cmdArgs)
 	if err != nil {
 		log.Fatal(err)
 		return
 	}
-	if !cfg.Log.Silent {
+	printStartupBanner(cfg, true)
-		printSplash()
-	}
 	if debugMode && !cfg.Log.Silent {
 		fmt.Println("[debug] mode")
 	}

runner/config.go

@@ -167,7 +167,8 @@ type cfgColor struct {
 }
 
 type cfgMisc struct {
-	CleanOnExit bool `toml:"clean_on_exit" usage:"Delete tmp directory on exit"`
+	CleanOnExit   bool    `toml:"clean_on_exit" usage:"Delete tmp directory on exit"`
+	StartupBanner *string `toml:"startup_banner" usage:"Custom startup banner text; set to empty string to hide banner"`
 }
 
 type cfgScreen struct {
@@ -197,7 +198,39 @@ func (t sliceTransformer) Transformer(typ reflect.Type) func(dst, src reflect.Va
 }
 
 // InitConfig initializes the configuration.
-func InitConfig(path string, cmdArgs map[string]TomlInfo) (cfg *Config, err error) {
+func InitConfig(path string, cmdArgs map[string]TomlInfo) (*Config, error) {
+	ret, err := initConfigWithoutPreprocess(path)
+	if err != nil {
+		return nil, err
+	}
+
+	err = ret.preprocess(cmdArgs)
+	if err != nil {
+		return nil, err
+	}
+	warnDeprecatedBin(ret)
+
+	return ret, nil
+}
+
+// InitConfigForDisplay initializes config without preprocess side effects.
+func InitConfigForDisplay(path string, cmdArgs map[string]TomlInfo) (*Config, error) {
+	ret, err := initConfigWithoutPreprocess(path)
+	if err != nil {
+		return nil, err
+	}
+	if cmdArgs != nil {
+		ret.withArgs(cmdArgs)
+	}
+	return ret, nil
+}
+
+func initConfigWithoutPreprocess(path string) (*Config, error) {
+	var (
+		cfg *Config
+		err error
+	)
+
 	if path == "" {
 		cfg, err = defaultPathConfig()
 		if err != nil {
@@ -226,13 +259,6 @@ func InitConfig(path string, cmdArgs map[string]TomlInfo) (cfg *Config, err erro
 	if err = applyPlatformOverrides(ret); err != nil {
 		return nil, err
 	}
-
-	err = ret.preprocess(cmdArgs)
-	if err != nil {
-		return nil, err
-	}
-	warnDeprecatedBin(ret)
-
 	return ret, nil
 }
 

runner/config_test.go

@@ -379,6 +379,115 @@ func TestDefaultConfigForOS(t *testing.T) {
 	if linuxCfg.Build.Bin != "./tmp/main" {
 		t.Fatalf("linux bin mismatch: got %q", linuxCfg.Build.Bin)
 	}
+	if linuxCfg.Misc.StartupBanner != nil {
+		t.Fatalf("startup_banner should default to nil, got %v", *linuxCfg.Misc.StartupBanner)
+	}
+}
+
+func TestWithArgsSetsStartupBanner(t *testing.T) {
+	t.Parallel()
+
+	t.Run("custom text", func(t *testing.T) {
+		cfg := defaultConfig()
+		fs := flag.NewFlagSet("test", flag.ContinueOnError)
+		args := ParseConfigFlag(fs)
+		value := "Watcher A"
+		info, ok := args["misc.startup_banner"]
+		if !ok {
+			t.Fatal("misc.startup_banner flag mapping missing")
+		}
+		*info.Value = value
+
+		cfg.withArgs(args)
+
+		if cfg.Misc.StartupBanner == nil {
+			t.Fatal("startup_banner should be set")
+		}
+		if got := *cfg.Misc.StartupBanner; got != value {
+			t.Fatalf("startup_banner mismatch: got %q want %q", got, value)
+		}
+	})
+
+	t.Run("empty string", func(t *testing.T) {
+		cfg := defaultConfig()
+		fs := flag.NewFlagSet("test", flag.ContinueOnError)
+		args := ParseConfigFlag(fs)
+		info, ok := args["misc.startup_banner"]
+		if !ok {
+			t.Fatal("misc.startup_banner flag mapping missing")
+		}
+		*info.Value = ""
+
+		cfg.withArgs(args)
+
+		if cfg.Misc.StartupBanner == nil {
+			t.Fatal("startup_banner should be set")
+		}
+		if got := *cfg.Misc.StartupBanner; got != "" {
+			t.Fatalf("startup_banner mismatch: got %q want empty", got)
+		}
+	})
+}
+
+func TestInitConfigForDisplayStartupBanner(t *testing.T) {
+	t.Parallel()
+
+	t.Run("reads empty string from config", func(t *testing.T) {
+		tmpDir := t.TempDir()
+		cfgPath := filepath.Join(tmpDir, ".air.toml")
+		cfgContent := `
+[misc]
+startup_banner = ""
+`
+		if err := os.WriteFile(cfgPath, []byte(cfgContent), 0o644); err != nil {
+			t.Fatalf("failed to write config: %v", err)
+		}
+
+		cfg, err := InitConfigForDisplay(cfgPath, nil)
+		if err != nil {
+			t.Fatalf("InitConfigForDisplay returned error: %v", err)
+		}
+
+		if cfg.Misc.StartupBanner == nil {
+			t.Fatal("startup_banner should be set")
+		}
+		if got := *cfg.Misc.StartupBanner; got != "" {
+			t.Fatalf("startup_banner mismatch: got %q want empty", got)
+		}
+	})
+
+	t.Run("applies command arg override", func(t *testing.T) {
+		tmpDir := t.TempDir()
+		cfgPath := filepath.Join(tmpDir, ".air.toml")
+		cfgContent := `
+[misc]
+startup_banner = "FromConfig"
+`
+		if err := os.WriteFile(cfgPath, []byte(cfgContent), 0o644); err != nil {
+			t.Fatalf("failed to write config: %v", err)
+		}
+
+		fs := flag.NewFlagSet("test", flag.ContinueOnError)
+		args := ParseConfigFlag(fs)
+		value := "FromFlag"
+		info, ok := args["misc.startup_banner"]
+		if !ok {
+			t.Fatal("misc.startup_banner flag mapping missing")
+		}
+		*info.Value = value
+
+		cfg, err := InitConfigForDisplay(cfgPath, args)
+		if err != nil {
+			t.Fatalf("InitConfigForDisplay returned error: %v", err)
+		}
+
+		if cfg.Misc.StartupBanner == nil {
+			t.Fatal("startup_banner should be set")
+		}
+		if got := *cfg.Misc.StartupBanner; got != value {
+			t.Fatalf("startup_banner mismatch: got %q want %q", got, value)
+		}
+	})
 }
 
 func TestPlatformBuildOverridesSelection(t *testing.T) {

runner/util.go

@@ -410,7 +410,12 @@ func setValue2Struct(v reflect.Value, fieldName string, value string) {
 			b, _ := strconv.ParseBool(value)
 			field.SetBool(b)
 		case reflect.Ptr:
-			field.SetString(value)
+			if field.Type().Elem().Kind() != reflect.String {
+				log.Fatalf("unsupported pointer type %s", field.Type().Elem().Kind())
+			}
+			v := reflect.New(field.Type().Elem())
+			v.Elem().SetString(value)
+			field.Set(v)
 		default:
 			log.Fatalf("unsupported type %s", v.FieldByName(fields[0]).Kind())
 		}