fix: return not found error if setting config

Author: Matthew Coleman

viper.go

@@ -76,7 +76,12 @@ type ConfigFileNotFoundError struct {
 
 // Error returns the formatted configuration error.
 func (fnfe ConfigFileNotFoundError) Error() string {
-	return fmt.Sprintf("Config File %q Not Found in %q", fnfe.name, fnfe.locations)
+	message := fmt.Sprintf("Config file %q Not Found", fnfe.name)
+	if fnfe.locations != "" {
+		message += fmt.Sprintf(" in %q", fnfe.locations)
+	}
+
+	return message
 }
 
 // ConfigFileAlreadyExistsError denotes failure to write new configuration file.
@@ -1522,11 +1527,16 @@ func (v *Viper) ReadInConfig() error {
 	}
 
 	v.logger.Debug("reading file", "file", filename)
+	exists, err := afero.Exists(v.fs, filename)
+	if !exists {
+		return ConfigFileNotFoundError{filename, ""}
+	} else if err != nil {
+		return err
+	}
 	file, err := afero.ReadFile(v.fs, filename)
 	if err != nil {
 		return err
 	}
-
 	config := make(map[string]any)
 
 	err = v.unmarshalReader(bytes.NewReader(file), config)

viper_test.go

@@ -359,7 +359,7 @@ func TestReadInConfig(t *testing.T) {
 	t.Run("config file set", func(t *testing.T) {
 		fs := afero.NewMemMapFs()
 
-		err := fs.Mkdir("/etc/viper", 0o777)
+		err := fs.Mkdir(testutil.AbsFilePath(t, "/etc/viper"), 0o777)
 		require.NoError(t, err)
 
 		file, err := fs.Create(testutil.AbsFilePath(t, "/etc/viper/config.yaml"))
@@ -1573,6 +1573,23 @@ func TestReadConfigWithSetConfigFile(t *testing.T) {
 	assert.Equal(t, 45000, v.GetInt("hello.pop"))
 }
 
+func TestWrongConfigWithSetConfigFileNotFound(t *testing.T) {
+	_, config := initDirs(t)
+
+	v := New()
+	v.SetConfigName(config)
+	v.SetDefault(`key`, `default`)
+
+	v.SetConfigFile(`whatareyoutalkingabout.yaml`)
+
+	err := v.ReadInConfig()
+	assert.IsType(t, ConfigFileNotFoundError{"", ""}, err)
+
+	// Even though config did not load and the error might have
+	// been ignored by the client, the default still loads
+	assert.Equal(t, `default`, v.GetString(`key`))
+}
+
 func TestIsSet(t *testing.T) {
 	v := New()
 	v.SetConfigType("yaml")