✨ Allow MYLOG_CONFIG_PATH to override the config path

AGENTS.md

@@ -22,7 +22,7 @@
 
 ## Config System
 - Viper instance is stored in context using a custom key type (`confKeyType`)
-- Use `config.New(path, overrides)` to create a new viper instance
+- Use `config.New(ctx, path)` to create a new viper instance
 - Use `config.RetrieveFromContext(ctx)` to get both viper and the unmarshaled Config struct
 - Formatters can use `v.Sub("formatters." + kind)` to get their own sub-config and unmarshal into their specific config struct
 - Test files must create viper instances and add them to context using `config.AddToContext`

cli/root.go

@@ -28,18 +28,11 @@ var RootCmd = &cobra.Command{
 	Use:   "my-log",
 	Short: "A brief description of your application",
 	PersistentPreRunE: func(cmd *cobra.Command, args []string) error {
-		ctx, v, err := config.New(cmd.Context())
-		if err != nil {
-			return err
-		}
 
-		if configPath != "" {
-			v.SetConfigFile(configPath)
-			err := v.ReadInConfig()
+		ctx, v, err := config.New(cmd.Context(), configPath)
 		if err != nil {
 			return err
 		}
-		}
 
 		for k, val := range configValues {
 			v.Set(k, val)
@@ -62,6 +55,10 @@ var configPath string
 var configValues map[string]string
 
 func init() {
-	RootCmd.PersistentFlags().StringVarP(&configPath, "config", "c", config.DefaultPath(), "config file")
+	path := os.Getenv("MYLOG_CONFIG_PATH")
+	if path == "" {
+		path = config.DefaultPath()
+	}
+	RootCmd.PersistentFlags().StringVarP(&configPath, "config", "c", path, "config file")
 	RootCmd.PersistentFlags().StringToStringVarP(&configValues, "config-value", "v", nil, "Override config values. Use dot syntax to specify key. E.g. -v formatters.preferred=json")
 }

config/load.go

@@ -32,7 +32,7 @@ func AddToContext(ctx context.Context, v *viper.Viper) context.Context {
 	return context.WithValue(ctx, viperKey, v)
 }
 
-func New(ctx context.Context) (context.Context, *viper.Viper, error) {
+func New(ctx context.Context, path string) (context.Context, *viper.Viper, error) {
 	v := viper.New()
 	v.SetConfigType("toml")
 
@@ -40,12 +40,16 @@ func New(ctx context.Context) (context.Context, *viper.Viper, error) {
 		return ctx, nil, err
 	}
 
-	v.SetConfigFile(DefaultPath())
+	if path == "" {
+		path = DefaultPath()
+	}
+
+	v.SetConfigFile(path)
 	v.SetEnvPrefix("MYLOG")
 	v.AutomaticEnv()
 	v.SetEnvKeyReplacer(strings.NewReplacer(".", "_", "-", "_"))
 
-	if err := v.ReadInConfig(); err != nil {
+	if err := v.MergeInConfig(); err != nil {
 		return ctx, nil, err
 	}
 

config/load_test.go

@@ -9,7 +9,7 @@ import (
 )
 
 func TestNew(t *testing.T) {
-	_, v, err := New(t.Context())
+	_, v, err := New(t.Context(), "")
 	be.Err(t, err, nil)
 	be.True(t, v != nil)
 }
@@ -18,7 +18,7 @@ func TestNewWithEnvOverrides(t *testing.T) {
 	os.Setenv("MYLOG_INPUT_PATH", "/test/path")
 	defer os.Unsetenv("MYLOG_INPUT_PATH")
 
-	_, v, err := New(t.Context())
+	_, v, err := New(t.Context(), "")
 	be.Err(t, err, nil)
 	be.Equal(t, v.GetString("input.path"), "/test/path")
 }
@@ -32,12 +32,9 @@ path = "/file/path"
 ext = "log"`)
 	f.Close()
 
-	_, v, err := New(t.Context())
+	_, v, err := New(t.Context(), f.Name())
 	be.Err(t, err, nil)
 
-	v.SetConfigFile(f.Name())
-	v.SetConfigType("toml")
-	err = v.ReadInConfig()
 	be.Err(t, err, nil)
 	be.Equal(t, v.GetString("input.path"), "/file/path")
 	be.Equal(t, v.GetString("input.ext"), "log")