fix(belongsToMany): otherKey should be inferred from paired foreignKey if undefined, fixes #2845

lib/associations/belongs-to-many.js

@@ -8,7 +8,13 @@ var Utils = require('./../utils')
   , Model = require('../model')
   , CounterCache = require('../plugins/counter-cache')
   , util = require('util')
-  , HasManyDoubleLinked = require('./has-many-double-linked');
+  , HasManyDoubleLinked = require('./has-many-double-linked')
+  , deprecatedSeen = {}
+  , deprecated = function(message) {
+    if (deprecatedSeen[message]) return;
+    console.warn(message);
+    deprecatedSeen[message] = true;
+  };
 
 module.exports = (function() {
   var BelongsToMany = function(source, target, options) {
@@ -36,10 +42,18 @@ module.exports = (function() {
       this.through = true;
     }
 
+    if (this.through) {
+      deprecated('belongsToMany: not defining through or defining through as true has been deprecated, please provide a string or a model');
+    }
+
     if (Utils._.isObject(this.options.foreignKey)) {
       this.foreignKeyAttribute = this.options.foreignKey;
       this.foreignKey = this.foreignKeyAttribute.name || this.foreignKeyAttribute.fieldName;
     } else {
+      if (!this.options.foreignKey) {
+        this.foreignKeyDefault = true;
+      }
+
       this.foreignKeyAttribute = {};
       this.foreignKey = this.options.foreignKey || Utils._.camelizeIf(
         [
@@ -54,6 +68,10 @@ module.exports = (function() {
       this.otherKeyAttribute = this.options.otherKey;
       this.otherKey = this.otherKeyAttribute.name || this.otherKeyAttribute.fieldName;
     } else {
+      if (!this.options.otherKey) {
+        this.otherKeyDefault = true;
+      }
+
       this.otherKeyAttribute = {};
       this.otherKey = this.options.otherKey || Utils._.camelizeIf(
         [
@@ -104,6 +122,23 @@ module.exports = (function() {
       this.through.model = this.combinedTableName;
     }
 
+    /*
+     * Find paired association (if exists)
+     */
+    _.each(this.target.associations, function(association, accessor) {
+      if (association.associationType !== 'BelongsToMany') return;
+      if (association.target !== this.source) return;
+      
+      if (this.options.through.model === association.options.through.model) {
+        this.paired = association;
+      }
+    }, this);
+
+    if (this.paired) {
+      if (this.otherKeyDefault) this.otherKey = this.paired.foreignKey;
+      if (this.paired.otherKeyDefault) this.paired.otherKey = this.foreignKey;
+    }
+
     if (typeof this.through.model === 'string') {
       if (!this.sequelize.isDefined(this.through.model)) {
         this.through.model = this.sequelize.define(this.through.model, {}, _.extend(this.options, {

test/associations/belongs-to-many.test.js

@@ -809,6 +809,35 @@ describe(Support.getTestDialectTeaser('BelongsToMany'), function() {
       expect(attributes.place_id).to.be.ok;
       expect(attributes.user_id).to.be.ok;
     });
+
+    it('should infer otherKey from paired BTM relationship with a through string defined', function () {
+      var User = this.sequelize.define('User', {});
+      var Place = this.sequelize.define('User', {});
+
+      var Places = User.belongsToMany(Place, { through: 'user_places', foreignKey: 'user_id' });
+      var Users = Place.belongsToMany(User, { through: 'user_places', foreignKey: 'place_id' });
+
+      expect(Places.foreignKey).to.equal('user_id');
+      expect(Users.foreignKey).to.equal('place_id');
+
+      expect(Places.otherKey).to.equal('place_id');
+      expect(Users.otherKey).to.equal('user_id');
+    });
+
+    it('should infer otherKey from paired BTM relationship with a through model defined', function () {
+      var User = this.sequelize.define('User', {});
+      var Place = this.sequelize.define('User', {});
+      var UserPlace = this.sequelize.define('UserPlace', {});
+
+      var Places = User.belongsToMany(Place, { through: UserPlace, foreignKey: 'user_id' });
+      var Users = Place.belongsToMany(User, { through: UserPlace, foreignKey: 'place_id' });
+
+      expect(Places.foreignKey).to.equal('user_id');
+      expect(Users.foreignKey).to.equal('place_id');
+
+      expect(Places.otherKey).to.equal('place_id');
+      expect(Users.otherKey).to.equal('user_id');
+    });
   });
 
   describe('foreign key with fields specified', function() {