Fix polymorphic hasMany inverse relation (#1621)

* Polymorphic hasMany inverse relation

* rename test suit to eslint error

.gitignore

@@ -6,6 +6,7 @@ v8.log
 .idea
 .DS_Store
 .git
+.vscode
 benchmark.js
 analyse.r
 docs/html

lib/include.js

@@ -437,8 +437,9 @@ Inclusion.include = function(objects, include, options, cb) {
       if (polymorphic) {
         // handle polymorphic hasMany (reverse) in which case we need to filter
         // by discriminator to filter other types
+        const throughModel = polymorphic.invert ? relation.modelTo : relation.modelFrom;
         throughFilter.where[polymorphic.discriminator] =
-          relation.modelFrom.definition.name;
+        throughModel.definition.name;
       }
 
       // 1st DB Call of 2-step process. Get through model objects first

test/relations.test.js

@@ -6621,4 +6621,35 @@ describe('relations', function() {
       }).should.throw('Invalid relation name: trigger');
     });
   });
+
+  describe('polymorphic hasMany - revert', function() {
+    before(function(done) {
+      Picture = db.define('Picture', {name: String});
+      Author = db.define('Author', {name: String});
+      PictureLink = db.define('PictureLink', {});
+      Author.hasMany(Picture, {through: PictureLink, polymorphic: 'imageable', invert: true});
+      Picture.hasMany(Author, {through: PictureLink, polymorphic: 'imageable'});
+      db.automigrate(['Picture', 'Author', 'PictureLink'], done);
+    });
+    it('should properly query through an inverted relationship', function(done) {
+      Author.create({name: 'Steve'}, function(err, author) {
+        if (err) {
+          return done(err);
+        }
+        author.pictures.create({name: 'Steve pic 1'}, function(err, pic) {
+          if (err) {
+            return done(err);
+          }
+          Author.findOne({include: 'pictures'}, function(err, author) {
+            if (err) {
+              return done(err);
+            }
+            author.pictures().length.should.eql(1);
+            author.pictures()[0].name.should.eql('Steve pic 1');
+            done();
+          });
+        });
+      });
+    });
+  });
 });