Pass `app` to fn exported by auto-required script

When a script in `models/` or `boot/` exports a function which is not
a loopback.Model constructor, the bootstrapper immediatelly calls
this exported function wit the current `app` object.

This is providing a dependency injection mechanism for boot scripts,
so that they no longer need to know where to find the `app` object.

Note: the dependency injection is optional. Existing code getting
`app` reference via `require('../app')` will continue to work.

index.js

@@ -2,6 +2,7 @@ var assert = require('assert');
 var fs = require('fs');
 var path = require('path');
 var _ = require('underscore');
+var loopback = require('loopback');
 var ConfigLoader = require('./lib/config-loader');
 
 /**
@@ -195,7 +196,7 @@ exports = module.exports = function bootLoopBackApp(app, options) {
 
   // try to attach models to dataSources by type
   try {
-    require('loopback').autoAttach();
+    loopback.autoAttach();
   } catch(e) {
     if(e.name === 'AssertionError') {
       console.warn(e);
@@ -213,8 +214,8 @@ exports = module.exports = function bootLoopBackApp(app, options) {
   }
 
   // require directories
-  requireDir(path.join(modelsRootDir, 'models'));
-  requireDir(path.join(appRootDir, 'boot'));
+  requireDir(path.join(modelsRootDir, 'models'), app);
+  requireDir(path.join(appRootDir, 'boot'), app);
 };
 
 function assertIsValidConfig(name, config) {
@@ -232,7 +233,7 @@ function forEachKeyedObject(obj, fn) {
   });
 }
 
-function requireDir(dir) {
+function requireDir(dir, app) {
   assert(dir, 'cannot require directory contents without directory name');
 
   var requires = {};
@@ -271,9 +272,12 @@ function requireDir(dir) {
       return;
     }
 
-    var basename = path.basename(filename, ext);
+    var exports = tryRequire(filepath);
+    if (isFunctionNotModelCtor(exports))
+      exports(app);
 
-    requires[basename] = tryRequire(filepath);
+    var basename = path.basename(filename, ext);
+    requires[basename] = exports;
   });
 
   return requires;
@@ -296,4 +300,9 @@ function tryReadDir() {
   }
 }
 
+function isFunctionNotModelCtor(fn) {
+ return typeof fn === 'function' &&
+   !(fn.prototype instanceof loopback.Model);
+}
+
 exports.ConfigLoader = ConfigLoader;

test/boot.test.js

@@ -342,6 +342,43 @@ describe('bootLoopBackApp', function() {
       expect(app.models).to.have.property('foo');
       expect(global.testData).to.have.property('foo', 'loaded');
     });
+
+    it('calls function exported by models/model.js', function() {
+      givenAppInSandbox();
+      writeAppFile('models/model.js',
+        'module.exports = function(app) { app.fnCalled = true; };');
+
+      var app = loopback();
+      delete app.fnCalled;
+      boot(app, appDir);
+      expect(app.fnCalled, 'exported fn was called').to.be.true();
+    });
+
+    it('calls function exported by boot/init.js', function() {
+      givenAppInSandbox();
+      writeAppFile('boot/init.js',
+        'module.exports = function(app) { app.fnCalled = true; };');
+
+      var app = loopback();
+      delete app.fnCalled;
+      boot(app, appDir);
+      expect(app.fnCalled, 'exported fn was called').to.be.true();
+    });
+
+    it('does not call Model ctor exported by models/model.json', function() {
+      givenAppInSandbox();
+      writeAppFile('models/model.js',
+        'var loopback = require("loopback");\n' +
+          'module.exports = loopback.Model.extend("foo");\n' +
+          'module.exports.prototype._initProperties = function() {\n' +
+          '  global.fnCalled = true;\n' +
+          '};');
+
+      var app = loopback();
+      delete global.fnCalled;
+      boot(app, appDir);
+      expect(global.fnCalled, 'exported fn was called').to.be.undefined();
+    });
   });
 });