V4 fix belongsto foreignkeys (#6650)

changelog.md

 # Future
 - [FIXED] Issues with `createFunction` and `dropFunction` (PostgresSQL)
-
+- [FIXED] Issue with belongsTo association and foreign keys [#6400](https://github.com/sequelize/sequelize/issues/6400)
 
 # 4.0.0-2
 - [ADDED] include now supports string as an argument (on top of model/association), string will expand into an association matched literally from Model.associations

lib/dialects/abstract/query-generator.js

@@ -1445,14 +1445,16 @@ const QueryGenerator = {
             includeIgnoreAttributes: false
           }, topInclude.through.model);
         } else {
+          const isBelongsTo = topInclude.association.associationType === 'BelongsTo';
+          const join = [
+            this.quoteTable(topParent.model.name) + '.' + this.quoteIdentifier(isBelongsTo ? topInclude.association.identifierField : topParent.model.primaryKeyAttributes[0]),
+            this.quoteIdentifier(topInclude.model.name) + '.' + this.quoteIdentifier(isBelongsTo ? topParent.model.primaryKeyAttributes[0] : topInclude.association.identifierField)
+          ].join(' = ');
           query = this.selectQuery(topInclude.model.tableName, {
             attributes: [topInclude.model.primaryKeyAttributes[0]],
             include: topInclude.include,
             where: {
-              $join: this.sequelize.asIs([
-                this.quoteTable(topParent.model.name) + '.' + this.quoteIdentifier(topParent.model.primaryKeyAttributes[0]),
-                this.quoteIdentifier(topInclude.model.name) + '.' + this.quoteIdentifier(topInclude.association.identifierField)
-              ].join(' = '))
+              $join: this.sequelize.asIs(join)
             },
             limit: 1,
             includeIgnoreAttributes: false

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

@@ -836,3 +836,96 @@ describe(Support.getTestDialectTeaser('BelongsTo'), function() {
     });
   });
 });
+
+describe('Association', function() {
+  it('should set foreignKey on foreign table', function () {
+    const Mail = this.sequelize.define('mail', {}, { timestamps: false });
+    const Entry = this.sequelize.define('entry', {}, { timestamps: false });
+    const User = this.sequelize.define('user', {}, { timestamps: false });
+    Entry.belongsTo(User, { as: 'owner', foreignKey: { name: 'ownerId', allowNull: false } });
+    Entry.belongsTo(Mail, {
+      as: 'mail',
+      foreignKey: {
+        name: 'mailId',
+        allowNull: false
+      }
+    });
+    Mail.belongsToMany(User, {
+      as: 'recipients',
+      through: 'MailRecipients',
+      otherKey: {
+        name: 'recipientId',
+        allowNull: false
+      },
+      foreignKey: {
+        name: 'mailId',
+        allowNull: false
+      },
+      timestamps: false
+    });
+    Mail.hasMany(Entry, {
+      as: 'entries',
+      foreignKey: {
+        name: 'mailId',
+        allowNull: false
+      }
+    });
+    User.hasMany(Entry, {
+      as: 'entries',
+      foreignKey: {
+        name: 'ownerId',
+        allowNull: false
+      }
+    });
+    return this.sequelize.sync({ force: true })
+      .then(() => User.create({}))
+      .then(() => Mail.create({}))
+      .then(mail =>
+        Entry.create({ mailId: mail.id, ownerId: 1 })
+          .then(() => Entry.create({ mailId: mail.id, ownerId: 1 }))
+          // set recipients
+          .then(() => mail.setRecipients([1]))
+      )
+      .then(() => Entry.findAndCount({
+        offset: 0,
+        limit: 10,
+        order: [['id', 'DESC']],
+        include: [
+          {
+            association: Entry.associations.mail,
+            include: [
+              {
+                association: Mail.associations.recipients,
+                through: {
+                  where: {
+                    recipientId: 1
+                  }
+                },
+                required: true
+              }
+            ],
+            required: true
+          }
+        ]
+      })).then(result => {
+        expect(result.count).to.equal(2);
+        expect(result.rows[0].get({ plain: true })).to.deep.equal(
+          {
+            id: 2,
+            ownerId: 1,
+            mailId: 1,
+            mail: {
+              id: 1,
+              recipients: [{
+                id: 1,
+                MailRecipients: {
+                  mailId: 1,
+                  recipientId: 1
+                }
+              }]
+            }
+          }
+        );
+      });
+  });
+});