Fix morphTo options.query

lib/eager.js

@@ -58,8 +58,9 @@ class EagerRelation extends EagerBase {
         const idAttribute = _.result(Target.prototype, 'idAttribute');
         const ids = getAttributeUnique(parents, idColumn);
 
+        // Remove `query` from options to not send the same query to all candidates
         return Target.query('whereIn', idAttribute, ids)
-          .sync(options)
+          .sync(_.assign({}, options, {query: undefined}))
           .select()
           .tap((response) => {
             const clone = relatedData.instance('morphTo', Target, {

test/integration/helpers/objects.js

@@ -409,7 +409,52 @@ module.exports = function(Bookshelf) {
     }
   });
 
+  function generateEventModels(eventHooks) {
+    var Photo = Bookshelf.Model.extend({
+      tableName: 'photos',
+      imageable: function() {
+        return this.morphTo('imageable', Site, [Author, 'profile_pic']);
+      }
+    });
+
+    var Site = Bookshelf.Model.extend({
+      tableName: 'sites',
+      photos: function() {
+        return this.morphMany(Photo, 'imageable');
+      },
+      initialize: function() {
+        this.constructor.__super__.initialize.apply(this, arguments);
+        this.on('fetching', function(model, columns, options) {
+          eventHooks.fetching('sites', model, columns, options);
+        });
+      }
+    });
+
+    var Author = Bookshelf.Model.extend({
+      tableName: 'authors',
+      site: function() {
+        return this.belongsTo(Site);
+      },
+      photo: function() {
+        return this.morphOne(Photo, 'imageable', 'profile_pic');
+      },
+      initialize: function() {
+        this.constructor.__super__.initialize.apply(this, arguments);
+        this.on('fetching', function(model, columns, options) {
+          eventHooks.fetching('authors', model, columns, options);
+        });
+      }
+    });
+
+    return {
+      Photo,
+      Site,
+      Author
+    };
+  }
+
   return {
+    generateEventModels,
     Models: {
       Site: Site,
       SiteParsed: SiteParsed,

test/integration/relations.js

@@ -1425,5 +1425,20 @@ module.exports = function(Bookshelf) {
           });
       });
     });
+
+    describe('PR #2059 - opts.query on fetching with morphTo', function() {
+      it('should correctly set query on fetching with morphTo', async function() {
+        const {Photo} = objs.generateEventModels({
+          fetching: function(table, model, columns, options) {
+            // Check that options.query actually queries this table
+            equal(options.query._single.table, table);
+          }
+        });
+
+        // Execute a query that will trigger fetching events
+        // These have assertions
+        return Photo.forge().fetchAll({withRelated: 'imageable'});
+      });
+    });
   });
 };