fix(associations): check presence of multi-joined instances (#10853)

When entities in a HABTM relationship can be joined more than once, we
need to rely on more than the resulting length for verification of
presence.

lib/associations/belongs-to-many.js

@@ -466,8 +466,6 @@ class BelongsToMany extends Association {
    * @returns {Promise<boolean>}
    * @returns {Promise<boolean>}
    */
    */
   has(sourceInstance, instances, options) {
   has(sourceInstance, instances, options) {
-    const where = {};
-
     if (!Array.isArray(instances)) {
     if (!Array.isArray(instances)) {
       instances = [instances];
       instances = [instances];
     }
     }
@@ -480,7 +478,7 @@ class BelongsToMany extends Association {
       joinTableAttributes: []
       joinTableAttributes: []
     });
     });
 
 
-    where[Op.or] = instances.map(instance => {
+    const instancePrimaryKeys = instances.map(instance => {
       if (instance instanceof this.target) {
       if (instance instanceof this.target) {
         return instance.where();
         return instance.where();
       }
       }
@@ -491,12 +489,14 @@ class BelongsToMany extends Association {
 
 
     options.where = {
     options.where = {
       [Op.and]: [
       [Op.and]: [
-        where,
+        { [Op.or]: instancePrimaryKeys },
         options.where
         options.where
       ]
       ]
     };
     };
 
 
-    return this.get(sourceInstance, options).then(associatedObjects => associatedObjects.length === instances.length);
+    return this.get(sourceInstance, options).then(associatedObjects =>
+      _.differenceBy(instancePrimaryKeys, associatedObjects, this.target.primaryKeyAttribute).length === 0
+    );
   }
   }
 
 
   /**
   /**

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

@@ -556,6 +556,93 @@ describe(Support.getTestDialectTeaser('BelongsToMany'), () => {
         });
         });
       });
       });
     });
     });
+
+    it('answers true for labels that have been assigned multitple times', function() {
+      this.ArticleLabel = this.sequelize.define('ArticleLabel', {
+        id: {
+          primaryKey: true,
+          type: DataTypes.INTEGER,
+          autoIncrement: true
+        },
+        relevance: {
+          type: DataTypes.DECIMAL,
+          validate: {
+            min: 0,
+            max: 1
+          }
+        }
+      });
+      this.Article.belongsToMany(this.Label, { through: { model: this.ArticleLabel, unique: false } });
+      this.Label.belongsToMany(this.Article, { through: { model: this.ArticleLabel, unique: false } });
+
+      return this.sequelize.sync({ force: true })
+        .then(() => Promise.all([
+          this.Article.create({ title: 'Article' }),
+          this.Label.create({ text: 'Awesomeness' }),
+          this.Label.create({ text: 'Epicness' })
+        ]))
+        .then(([article, label1, label2]) => Promise.all([
+          article,
+          label1,
+          label2,
+          article.addLabel(label1, {
+            through: { relevance: 1 }
+          }),
+          article.addLabel(label2, {
+            through: { relevance: .54 }
+          }),
+          article.addLabel(label2, {
+            through: { relevance: .99 }
+          })
+        ]))
+        .then(([article, label1, label2]) => article.hasLabels([label1, label2]))
+        .then(result => expect(result).to.be.true);
+    });
+
+    it('answers true for labels that have been assigned multitple times when passing a primary key instead of an object', function() {
+      this.ArticleLabel = this.sequelize.define('ArticleLabel', {
+        id: {
+          primaryKey: true,
+          type: DataTypes.INTEGER,
+          autoIncrement: true
+        },
+        relevance: {
+          type: DataTypes.DECIMAL,
+          validate: {
+            min: 0,
+            max: 1
+          }
+        }
+      });
+      this.Article.belongsToMany(this.Label, { through: { model: this.ArticleLabel, unique: false } });
+      this.Label.belongsToMany(this.Article, { through: { model: this.ArticleLabel, unique: false } });
+
+      return this.sequelize.sync({ force: true })
+        .then(() => Promise.all([
+          this.Article.create({ title: 'Article' }),
+          this.Label.create({ text: 'Awesomeness' }),
+          this.Label.create({ text: 'Epicness' })
+        ]))
+        .then(([article, label1, label2]) => Promise.all([
+          article,
+          label1,
+          label2,
+          article.addLabel(label1, {
+            through: { relevance: 1 }
+          }),
+          article.addLabel(label2, {
+            through: { relevance: .54 }
+          }),
+          article.addLabel(label2, {
+            through: { relevance: .99 }
+          })
+        ]))
+        .then(([article, label1, label2]) => article.hasLabels([
+          label1[this.Label.primaryKeyAttribute],
+          label2[this.Label.primaryKeyAttribute]
+        ]))
+        .then(result => expect(result).to.be.true);
+    });
   });
   });
 
 
   describe('countAssociations', () => {
   describe('countAssociations', () => {