feat(aliases): added support for env. var. aliases, fixes #5

FGRibreau · May 18, 2015 · dc74a02 · dc74a02
1 parent 25a986b
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diff --git a/README.md b/README.md
@@ -50,6 +50,36 @@ t.strictEqual(config.amqp.exchanges[0].name, 'new_exchange'); // extracted from
 t.strictEqual(config.FULL_UPPER_CASE.PORT, 8080);
 ```
 
+## Specifying multiple aliases
+
+It sometimes useful to be able to specify aliases, for instance [Clever-cloud](http://clever-cloud.com) or [Heroku](https://heroku.com) exposes their own environment variable names while your application's internal code may not want to rely on them. 
+
+Common-env adds a [layer of indirection](http://en.wikipedia.org/wiki/Fundamental_theorem_of_software_engineering) enabling you to specify environment aliases that won't impact your codebase.
+
+#### Usage
+
+```javascript
+var config = env.getOrElseAll({
+  amqp: {
+    login: {
+      $default: 'guest',
+      $aliases: ['ADDON_RABBITMQ_LOGIN', 'LOCAL_RABBITMQ_LOGIN']
+    },
+    password: 'guest',
+    host: 'localhost',
+    port: 5672
+  },
+});
+
+t.strictEqual(config.amqp.login, 'plop'); // converted from env
+```
+
+#### How common-env resolves `config.amqp.login`
+
+- Common-env will first read `ADDON_RABBITMQ_LOGIN` environment variable, if it exists, its value will be used.
+- If not common-env will read `LOCAL_RABBITMQ_LOGIN`, if it exists, its value will be used.
+- If not common-env will read `AMQP_LOGIN`, if it exists, its value will be used.
+- If not common-env will fallback on `$default` value.
 
 <p align="center">
 <img style="width:100%" src="./docs/Thumbs-Up-Gif.gif"/>

diff --git a/lib/common-env.js b/lib/common-env.js
@@ -16,58 +16,91 @@ function env(logger, options) {
     logger.info.apply(logger, arguments);
   }
 
-  return {
-    getOrElse: function (key, def) {
-      if (_.has(process.env, key)) {
-        var val = _.isNumber(def) ? toInt(process.env[key]) : process.env[key];
-
-        if (seemsBoolean(val)) {
-          val = String(val).toLowerCase() === 'true';
-        }
+  /**
+   * @param  {[type]} key [description]
+   * @param  {[type]} def [description]
+   * @return {undefined|mixed} yield undefined if not found
+   */
+  function getEnv(key, def) {
+    if (!_.has(process.env, key)) {
+      return def;
+    }
 
-        if (!PRINTED[key]) {
-          PRINTED[key] = 1;
-          log('[env] ' + key + ' was defined' + (options.displayValues ? ', using ' + String(val) : ''));
-        }
+    var val = _.isNumber(def) ? toInt(process.env[key]) : process.env[key];
+    if (seemsBoolean(val)) {
+      val = String(val).toLowerCase() === 'true';
+    }
+    return val;
+  }
 
-        return val;
-      }
 
+  function getOrElse(key, def) {
+    var val = getEnv(key, def);
+    if (val !== void 0) {
       if (!PRINTED[key]) {
         PRINTED[key] = 1;
-        log('[env] ' + key + ' was not defined, using default', String(def));
+        log('[env] ' + key + ' was defined' + (options.displayValues ? ', using ' + String(val) : ''));
       }
-      return def;
-    },
+
+      return val;
+    }
+
+    if (!PRINTED[key]) {
+      PRINTED[key] = 1;
+      log('[env] ' + key + ' was not defined, using default', String(def));
+    }
+    return def;
+  }
+
+  return {
+    getOrElse: getOrElse,
 
     /**
      * [getOrElseAll description]
      * @param  {Object} obj pair or {"ENV_VAR": {Number|String} defaultValue, ...}
      * @return {Object}     [description]
      */
-    getOrElseAll: function (vars, prefix) {
+    getOrElseAll: function getOrElseAll(vars, prefix) {
       prefix = prefix || '';
 
       return _.reduce(vars, function (out, val, k) {
         var keyEnvName = k.toUpperCase();
+        var fullKeyName = prefix + keyEnvName;
+
+        if (_.isPlainObject(val) && _.has(val, '$default')) {
+          if (!Array.isArray(val.$aliases)) {
+            throw new Error('Common-env: $aliases must be defined along side $default, key: ' + fullKeyName);
+          }
+          /*
+            "val":{
+              "$default": 1,
+              "$aliases": ['VAR_ENV', 'VAR_ENV2']
+            }
+
+            Will first try `VAR_ENV` then `VAR_ENV2` then `VAL` then fallback on `$default` if none of them were set
+          */
+          out[k] = val.$aliases.concat([fullKeyName]).reduce(function (memo, varEnvName, i, arr) {
+            return memo === void 0 ? getEnv(varEnvName, i === arr.length - 1 ? val.$default : void 0) : memo;
+          }, void 0);
 
-        if (_.isPlainObject(val)) {
-          out[k] = _.extend({}, this.getOrElseAll(val, prefix + keyEnvName + '_'));
-        } else if (_.isArray(val)) {
+        } else if (_.isPlainObject(val)) {
+          out[k] = _.extend({}, getOrElseAll(val, fullKeyName + '_'));
+        } else
+        if (_.isArray(val)) {
           out[k] = val.map(function (innerVal, index) {
-            return this.getOrElseAll(innerVal, prefix + keyEnvName + '[' + index + ']_');
-          }, this);
+            return getOrElseAll(innerVal, fullKeyName + '[' + index + ']_');
+          });
         } else {
-          out[k] = this.getOrElse(prefix + keyEnvName, val);
+          out[k] = getOrElse(fullKeyName, val);
         }
         return out;
-      }.bind(this), {});
+      }, {});
     },
 
     getOrDie: function (key) {
       // @todo refactor this shit.
-      var r = this.getOrElse(key, false);
-      if (r === false) {
+      var r = getOrElse(key, undefined);
+      if (r === void 0) {
         throw new Error('(env) ' + key + ' MUST be defined');
       }
       return r;

diff --git a/test/env.test.js b/test/env.test.js
@@ -116,6 +116,31 @@ describe('env', function () {
       t.ok(logger.hasENV('PLOP_API[1]_A'), 'PLOP_ROOT_TOKEN');
     });
 
+    it('should handle special $aliases and $default object value', function () {
+      var config = env.getOrElseAll({
+        a: {
+          b: [{
+            a: {
+              $default: 'heyheyhey',
+              $aliases: ['BLABLA_BLABLA', 'AMQP_LOGIN']
+            }
+          }, {
+            a: {
+              $default: 'plop2',
+              $aliases: ['BLABLA_BLABLA'] // `BLABLA_BLABLA` does not exist, it should fallback on "plop"
+            }
+          }]
+        },
+        b: {
+          $default: 'heyheyhey',
+          $aliases: ['BLABLA_BLABLA', 'AMQP_LOGIN', 'BLABLA_BLABLA']
+        }
+      });
+      t.strictEqual(config.a.b[0].a, 'plop');
+      t.strictEqual(config.a.b[1].a, 'plop2');
+      t.strictEqual(config.b, 'plop');
+    });
+
     afterEach(function () {
       delete process.env.AMQP_LOGIN;
       delete process.env.AMQP_CONNECT;