Update functionality of globals config

* The implicit default is `false` -- no globals at all
* If `sails.config.globals` is not `false`, it must be a dictionary such that:
  - If `sails.config.globals._` is not `false`, it must be an object
  - If `sails.config.globals.async` is not `false`, it must be an object
  - `sails.config.globals.models` must be a boolean
  - `sails.config.globals.sails` must be a boolean
* `sails.config.globals.services` still defaults to `true` if ``sails.config.globals` is a dictionary, because otherwise we have to talk about it explicitly and we're trying to phase services out.

lib/app/private/exposeGlobals.js

@@ -3,6 +3,7 @@
  */
 
 var _ = require('@sailshq/lodash');
+var flaverr = require('flaverr');
 var async = require('async');
 
 
@@ -18,30 +19,60 @@ var async = require('async');
 module.exports = function exposeGlobals() {
   var sails = this;
 
+  // Implicit default for globals is `false`.
+  // Note that this may not be what the default `config/globals.js`
+  // settings are.
+  if (_.isUndefined(sails.config.globals)) {
+    sails.config.globals = false;
+    return;
+  }
 
-  // Globals explicitly disabled
+  // If globals config is provided, it must be either `false` or a dictionary.
+  else if (sails.config.globals !== false && (!_.isObject(sails.config.globals) || _.isArray(sails.config.globals) || _.isFunction(sails.config.globals))) {
+    throw flaverr('E_BAD_GLOBAL_CONFIG', new Error('If `sails.config.globals` is defined, it must either be a dictionary or `false`'));
+  }
+
+  // Globals explicitly disabled.
   if (sails.config.globals === false) {
     sails.log.verbose('No global variables will be exposed.');
     return;
   }
 
   sails.log.verbose('Exposing global variables... (you can customize/disable this by modifying the properties in `sails.config.globals`.  Set it to `false` to disable all globals.)');
 
-  sails.config.globals = sails.config.globals || {};
-
-  // Provide global access (if allowed in config)
+  // `sails.config.globals._` must be false or an object.
+  // (it's probably a function with lots of extra properties, but to future-proof, we'll allow any type of object)
   if (sails.config.globals._ !== false) {
-    global['_'] = _;
+    if (!_.isObject(sails.config.globals._)) {
+      throw flaverr('E_BAD_GLOBAL_CONFIG', new Error('If `sails.config.globals._` is defined, it must be either `false` or an object.'));
+    }
+    global['_'] = sails.config.globals._;
   }
+  // `sails.config.globals.async` must be false or an object.
+  // (it's probably a plain object aka dictionary, but to future-proof, we'll allow any type of object)
   if (sails.config.globals.async !== false) {
-    global['async'] = async;
+    if (!_.isObject(sails.config.globals.async)) {
+      throw flaverr('E_BAD_GLOBAL_CONFIG', new Error('If `sails.config.globals.async` is defined, it must be either `false` or an object.'));
+    }
+    global['async'] = sails.config.globals.async;
   }
+
+  // `sails.config.globals.sails` must be a boolean
   if (sails.config.globals.sails !== false) {
+    if (sails.config.globals.sails !== true) {
+      throw flaverr('E_BAD_GLOBAL_CONFIG', new Error('If `sails.config.globals` is defined, then `sails.config.globals.sails` must be a boolean.'));
+    }
     global['sails'] = sails;
   }
 
-  // `services` hook takes care of globalizing services (if enabled)
+  // `sails.config.globals.models` must be a boolean.
+  // `orm` hook takes care of actually globalizing models and adapters (if enabled)
+  if (sails.config.globals.models !== false && sails.config.globals.models !== true) {
+    throw flaverr('E_BAD_GLOBAL_CONFIG', new Error('If `sails.config.globals` is defined, then `sails.config.globals.models` must be a boolean.'));
+  }
 
-  // `orm` hook takes care of globalizing models and adapters (if enabled)
+  // `services` hook takes care of globalizing services (if enabled)
+  // It does this by default for now, so that we don't have to document configuring
+  // services, which we're trying to phase out in favor of helpers.
 
 };

test/hooks/views/res.render.i18n.js

@@ -38,7 +38,7 @@ describe('sails.hooks.views.render() with i18n', function (){
   before(function (done) {
     app = new Sails()
     .load({
-      globals: true,
+      globals: { sails: true, models: false, _: false, async: false, services: false } ,
       loadHooks: [
         'moduleloader',
         'userconfig',