feat: expose set config meta (#227)

Author: atian25

lib/loader/mixin/config.js

@@ -6,8 +6,6 @@ const extend = require('extend2');
 const assert = require('assert');
 const { Console } = require('console');
 
-const SET_CONFIG_META = Symbol('Loader#setConfigMeta');
-
 module.exports = {
 
   /**
@@ -94,7 +92,7 @@ module.exports = {
     }
 
     // store config meta, check where is the property of config come from.
-    this[SET_CONFIG_META](config, filepath);
+    this._setConfigMeta(config, filepath);
 
     return config;
   },
@@ -104,14 +102,14 @@ module.exports = {
     if (!envConfigStr) return;
     try {
       const envConfig = JSON.parse(envConfigStr);
-      this[SET_CONFIG_META](envConfig, '<process.env.EGG_APP_CONFIG>');
+      this._setConfigMeta(envConfig, '<process.env.EGG_APP_CONFIG>');
       return envConfig;
     } catch (err) {
       this.options.logger.warn('[egg-loader] process.env.EGG_APP_CONFIG is not invalid JSON: %s', envConfigStr);
     }
   },
 
-  [SET_CONFIG_META](config, filepath) {
+  _setConfigMeta(config, filepath) {
     config = extend(true, {}, config);
     setConfig(config, filepath);
     extend(true, this.configMeta, config);