fix(ReadPreference): only allow valid ReadPreference modes

Fixes NODE-1425

Author: kvwalker

lib/core/topologies/read_preference.js

@@ -12,6 +12,10 @@
  * @return {ReadPreference}
  */
 const ReadPreference = function(mode, tags, options) {
+  if (!ReadPreference.isValid(mode)) {
+    throw new TypeError(`provided mode ${mode} is an invalid ReadPreference mode`);
+  }
+
   // TODO(major): tags MUST be an array of tagsets
   if (tags && !Array.isArray(tags)) {
     console.warn(
@@ -43,7 +47,7 @@ const ReadPreference = function(mode, tags, options) {
     this.minWireVersion = 5;
   }
 
-  if (this.mode === ReadPreference.PRIMARY || this.mode === true) {
+  if (this.mode === ReadPreference.PRIMARY) {
     if (this.tags && Array.isArray(this.tags) && this.tags.length > 0) {
       throw new TypeError('Primary read preference cannot be combined with tags');
     }
@@ -77,8 +81,8 @@ const VALID_MODES = [
   ReadPreference.SECONDARY,
   ReadPreference.SECONDARY_PREFERRED,
   ReadPreference.NEAREST,
-  true,
-  false,
+  // true,
+  // false,
   null
 ];
 

test/functional/readpreference_tests.js

@@ -1,6 +1,7 @@
 'use strict';
 var test = require('./shared').assert;
 var setupDatabase = require('./shared').setupDatabase;
+const expect = require('chai').expect;
 
 describe('ReadPreference', function() {
   before(function() {
@@ -546,4 +547,18 @@ describe('ReadPreference', function() {
       });
     }
   });
+
+  it('Should throw an error on an invalid readPreference', function(done) {
+    const configuration = this.configuration;
+
+    const client = configuration.newClient();
+    client.connect((err, client) => {
+      const db = client.db(configuration.db);
+      expect(db.collection.bind(db, 'test', { readPreference: 'invalid' })).to.throw(
+        'provided mode invalid is an invalid ReadPreference mode'
+      );
+      client.close();
+      done();
+    });
+  });
 });