fix: normalize include with boolean or number

- On include = true or include = 1 the lib crashes with
  "TypeError: includes.forEach is not a function".
- checking for boolean and number type and return empty array.
- fix: include symbol and function in normalization
- fix: review changes; adding debug stmt + early exit for tests

lib/include.js

@@ -5,6 +5,7 @@
 'use strict';
 
 var async = require('async');
+var debug = require('debug')('loopback:include');
 var g = require('strong-globalize')();
 var utils = require('./utils');
 var List = require('./list');
@@ -14,6 +15,8 @@ var defineCachedRelations = utils.defineCachedRelations;
 var uniq = utils.uniq;
 var idName = utils.idName;
 
+var DISALLOWED_TYPES = ['boolean', 'number', 'symbol', 'function'];
+
 /*!
  * Normalize the include to be an array
  * @param include
@@ -45,6 +48,9 @@ function normalizeInclude(include) {
       newInclude = newInclude.concat(subIncludes);
     }
     return newInclude;
+  } else if (DISALLOWED_TYPES.includes(typeof include)) {
+    debug('Ignoring invalid "include" value of type %s:', typeof include, include);
+    return [];
   } else {
     return include;
   }

test/include.test.js

@@ -420,6 +420,43 @@ describe('include', function() {
     });
   });
 
+  it('should not throw on fetch User if include is boolean equals true', function(done) {
+    User.find({include: true}, function(err, users) {
+      if (err) return done(err);
+      should.exist(users);
+      users.should.not.be.empty();
+      done();
+    });
+  });
+
+  it('should not throw on fetch User if include is number', function(done) {
+    User.find({include: 1}, function(err, users) {
+      if (err) return done(err);
+      should.exist(users);
+      users.should.not.be.empty();
+      done();
+    });
+  });
+
+  it('should not throw on fetch User if include is symbol', function(done) {
+    User.find({include: Symbol('include')}, function(err, users) {
+      if (err) return done(err);
+      should.exist(users);
+      users.should.not.be.empty();
+      done();
+    });
+  });
+
+  it('should not throw on fetch User if include is function', function(done) {
+    var include = function() {};
+    User.find({include: include}, function(err, users) {
+      if (err) return done(err);
+      should.exist(users);
+      users.should.not.be.empty();
+      done();
+    });
+  });
+
   // Not implemented correctly, see: loopback-datasource-juggler/issues/166
   // fixed by DB optimization
   it('should support include scope on hasAndBelongsToMany', function(done) {