sequelize/lib/associations/belongs-to-many.js

Sequelize is a promise-based Node.js ORM tool for Postgres, MySQL, MariaDB, SQLite, Microsoft SQL Server, Amazon Redshift and Snowflake’s Data Cloud. It features solid transaction support, relations, eager and lazy loading, read replication and more.

'use strict';

const Utils = require('./../utils');
const Helpers = require('./helpers');
const _ = require('lodash');
const Association = require('./base');
const BelongsTo = require('./belongs-to');
const HasMany = require('./has-many');
const HasOne = require('./has-one');
const AssociationError = require('../errors').AssociationError;
const EmptyResultError = require('../errors').EmptyResultError;
const Op = require('../operators');

/**
 * Many-to-many association with a join table.
 *
 * When the join table has additional attributes, these can be passed in the options object:
 *
 * ```js
 * UserProject = sequelize.define('user_project', {
 *   role: Sequelize.STRING
 * });
 * User.belongsToMany(Project, { through: UserProject });
 * Project.belongsToMany(User, { through: UserProject });
 * // through is required!
 *
 * user.addProject(project, { through: { role: 'manager' }});
 * ```
 *
 * All methods allow you to pass either a persisted instance, its primary key, or a mixture:
 *
 * ```js
 * const project = await Project.create({ id: 11 });
 * await user.addProjects([project, 12]);
 * ```
 *
 * If you want to set several target instances, but with different attributes you have to set the attributes on the instance, using a property with the name of the through model:
 *
 * ```js
 * p1.UserProjects = {
 *   started: true
 * }
 * user.setProjects([p1, p2], { through: { started: false }}) // The default value is false, but p1 overrides that.
 * ```
 *
 * Similarly, when fetching through a join table with custom attributes, these attributes will be available as an object with the name of the through model.
 * ```js
 * const projects = await user.getProjects();
 * const p1 = projects[0];
 * p1.UserProjects.started // Is this project started yet?
 * ```
 *
 * In the API reference below, add the name of the association to the method, e.g. for `User.belongsToMany(Project)` the getter will be `user.getProjects()`.
 *
 * @see {@link Model.belongsToMany}
 */
class BelongsToMany extends Association {
  constructor(source, target, options) {
    super(source, target, options);

    if (this.options.through === undefined || this.options.through === true || this.options.through === null) {
      throw new AssociationError(`${source.name}.belongsToMany(${target.name}) requires through option, pass either a string or a model`);
    }

    if (!this.options.through.model) {
      this.options.through = {
        model: options.through
      };
    }

    this.associationType = 'BelongsToMany';
    this.targetAssociation = null;
    this.sequelize = source.sequelize;
    this.through = { ...this.options.through };
    this.isMultiAssociation = true;
    this.doubleLinked = false;

    if (!this.as && this.isSelfAssociation) {
      throw new AssociationError('\'as\' must be defined for many-to-many self-associations');
    }

    if (this.as) {
      this.isAliased = true;

      if (_.isPlainObject(this.as)) {
        this.options.name = this.as;
        this.as = this.as.plural;
      } else {
        this.options.name = {
          plural: this.as,
          singular: Utils.singularize(this.as)
        };
      }
    } else {
      this.as = this.target.options.name.plural;
      this.options.name = this.target.options.name;
    }

    this.combinedTableName = Utils.combineTableNames(
      this.source.tableName,
      this.isSelfAssociation ? this.as || this.target.tableName : this.target.tableName
    );

    /*
    * If self association, this is the target association - Unless we find a pairing association
    */
    if (this.isSelfAssociation) {
      this.targetAssociation = this;
    }

    /*
    * Find paired association (if exists)
    */
    _.each(this.target.associations, association => {
      if (association.associationType !== 'BelongsToMany') return;
      if (association.target !== this.source) return;

      if (this.options.through.model === association.options.through.model) {
        this.paired = association;
        association.paired = this;
      }
    });

    /*
    * Default/generated source/target keys
    */
    this.sourceKey = this.options.sourceKey || this.source.primaryKeyAttribute;
    this.sourceKeyField = this.source.rawAttributes[this.sourceKey].field || this.sourceKey;

    if (this.options.targetKey) {
      this.targetKey = this.options.targetKey;
      this.targetKeyField = this.target.rawAttributes[this.targetKey].field || this.targetKey;
    } else {
      this.targetKeyDefault = true;
      this.targetKey = this.target.primaryKeyAttribute;
      this.targetKeyField = this.target.rawAttributes[this.targetKey].field || this.targetKey;
    }

    this._createForeignAndOtherKeys();

    if (typeof this.through.model === 'string') {
      if (!this.sequelize.isDefined(this.through.model)) {
        this.through.model = this.sequelize.define(this.through.model, {}, Object.assign(this.options, {
          tableName: this.through.model,
          indexes: [], //we don't want indexes here (as referenced in #2416)
          paranoid: this.through.paranoid ? this.through.paranoid : false, // Default to non-paranoid join (referenced in #11991)
          validate: {} // Don't propagate model-level validations
        }));
      } else {
        this.through.model = this.sequelize.model(this.through.model);
      }
    }

    Object.assign(this.options, _.pick(this.through.model.options, [
      'timestamps', 'createdAt', 'updatedAt', 'deletedAt', 'paranoid'
    ]));

    if (this.paired) {
      let needInjectPaired = false;

      if (this.targetKeyDefault) {
        this.targetKey = this.paired.sourceKey;
        this.targetKeyField = this.paired.sourceKeyField;
        this._createForeignAndOtherKeys();
      }
      if (this.paired.targetKeyDefault) {
        // in this case paired.otherKey depends on paired.targetKey,
        // so cleanup previously wrong generated otherKey
        if (this.paired.targetKey !== this.sourceKey) {
          delete this.through.model.rawAttributes[this.paired.otherKey];
          this.paired.targetKey = this.sourceKey;
          this.paired.targetKeyField = this.sourceKeyField;
          this.paired._createForeignAndOtherKeys();
          needInjectPaired = true;
        }
      }

      if (this.otherKeyDefault) {
        this.otherKey = this.paired.foreignKey;
      }
      if (this.paired.otherKeyDefault) {
        // If paired otherKey was inferred we should make sure to clean it up
        // before adding a new one that matches the foreignKey
        if (this.paired.otherKey !== this.foreignKey) {
          delete this.through.model.rawAttributes[this.paired.otherKey];
          this.paired.otherKey = this.foreignKey;
          needInjectPaired = true;
        }
      }

      if (needInjectPaired) {
        this.paired._injectAttributes();
      }
    }

    if (this.through) {
      this.throughModel = this.through.model;
    }

    this.options.tableName = this.combinedName = this.through.model === Object(this.through.model) ? this.through.model.tableName : this.through.model;

    this.associationAccessor = this.as;

    // Get singular and plural names, trying to uppercase the first letter, unless the model forbids it
    const plural = _.upperFirst(this.options.name.plural);
    const singular = _.upperFirst(this.options.name.singular);

    this.accessors = {
      get: `get${plural}`,
      set: `set${plural}`,
      addMultiple: `add${plural}`,
      add: `add${singular}`,
      create: `create${singular}`,
      remove: `remove${singular}`,
      removeMultiple: `remove${plural}`,
      hasSingle: `has${singular}`,
      hasAll: `has${plural}`,
      count: `count${plural}`
    };
  }

  _createForeignAndOtherKeys() {
    /*
    * Default/generated foreign/other keys
    */
    if (_.isObject(this.options.foreignKey)) {
      this.foreignKeyAttribute = this.options.foreignKey;
      this.foreignKey = this.foreignKeyAttribute.name || this.foreignKeyAttribute.fieldName;
    } else {
      this.foreignKeyAttribute = {};
      this.foreignKey = this.options.foreignKey || Utils.camelize(
        [
          this.source.options.name.singular,
          this.sourceKey
        ].join('_')
      );
    }

    if (_.isObject(this.options.otherKey)) {
      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.camelize(
        [
          this.isSelfAssociation ? Utils.singularize(this.as) : this.target.options.name.singular,
          this.targetKey
        ].join('_')
      );
    }
  }

  // the id is in the target table
  // or in an extra table which connects two tables
  _injectAttributes() {
    this.identifier = this.foreignKey;
    this.foreignIdentifier = this.otherKey;

    // remove any PKs previously defined by sequelize
    // but ignore any keys that are part of this association (#5865)
    _.each(this.through.model.rawAttributes, (attribute, attributeName) => {
      if (attribute.primaryKey === true && attribute._autoGenerated === true) {
        if ([this.foreignKey, this.otherKey].includes(attributeName)) {
          // this key is still needed as it's part of the association
          // so just set primaryKey to false
          attribute.primaryKey = false;
        }
        else {
          delete this.through.model.rawAttributes[attributeName];
        }
        this.primaryKeyDeleted = true;
      }
    });

    const sourceKey = this.source.rawAttributes[this.sourceKey];
    const sourceKeyType = sourceKey.type;
    const sourceKeyField = this.sourceKeyField;
    const targetKey = this.target.rawAttributes[this.targetKey];
    const targetKeyType = targetKey.type;
    const targetKeyField = this.targetKeyField;
    const sourceAttribute = { type: sourceKeyType, ...this.foreignKeyAttribute };
    const targetAttribute = { type: targetKeyType, ...this.otherKeyAttribute };

    if (this.primaryKeyDeleted === true) {
      targetAttribute.primaryKey = sourceAttribute.primaryKey = true;
    } else if (this.through.unique !== false) {
      let uniqueKey;
      if (typeof this.options.uniqueKey === 'string' && this.options.uniqueKey !== '') {
        uniqueKey = this.options.uniqueKey;
      } else {
        uniqueKey = [this.through.model.tableName, this.foreignKey, this.otherKey, 'unique'].join('_');
      }
      targetAttribute.unique = sourceAttribute.unique = uniqueKey;
    }

    if (!this.through.model.rawAttributes[this.foreignKey]) {
      this.through.model.rawAttributes[this.foreignKey] = {
        _autoGenerated: true
      };
    }

    if (!this.through.model.rawAttributes[this.otherKey]) {
      this.through.model.rawAttributes[this.otherKey] = {
        _autoGenerated: true
      };
    }

    if (this.options.constraints !== false) {
      sourceAttribute.references = {
        model: this.source.getTableName(),
        key: sourceKeyField
      };
      // For the source attribute the passed option is the priority
      sourceAttribute.onDelete = this.options.onDelete || this.through.model.rawAttributes[this.foreignKey].onDelete;
      sourceAttribute.onUpdate = this.options.onUpdate || this.through.model.rawAttributes[this.foreignKey].onUpdate;

      if (!sourceAttribute.onDelete) sourceAttribute.onDelete = 'CASCADE';
      if (!sourceAttribute.onUpdate) sourceAttribute.onUpdate = 'CASCADE';

      targetAttribute.references = {
        model: this.target.getTableName(),
        key: targetKeyField
      };
      // But the for target attribute the previously defined option is the priority (since it could've been set by another belongsToMany call)
      targetAttribute.onDelete = this.through.model.rawAttributes[this.otherKey].onDelete || this.options.onDelete;
      targetAttribute.onUpdate = this.through.model.rawAttributes[this.otherKey].onUpdate || this.options.onUpdate;

      if (!targetAttribute.onDelete) targetAttribute.onDelete = 'CASCADE';
      if (!targetAttribute.onUpdate) targetAttribute.onUpdate = 'CASCADE';
    }

    Object.assign(this.through.model.rawAttributes[this.foreignKey], sourceAttribute);
    Object.assign(this.through.model.rawAttributes[this.otherKey], targetAttribute);

    this.through.model.refreshAttributes();

    this.identifierField = this.through.model.rawAttributes[this.foreignKey].field || this.foreignKey;
    this.foreignIdentifierField = this.through.model.rawAttributes[this.otherKey].field || this.otherKey;

    // For Db2 server, a reference column of a FOREIGN KEY must be unique
    // else, server throws SQL0573N error. Hence, setting it here explicitly
    // for non primary columns.
    if (this.options.sequelize.options.dialect === 'db2' &&
        this.source.rawAttributes[this.sourceKey].primaryKey !== true) {
      this.source.rawAttributes[this.sourceKey].unique = true;
    }

    if (this.paired && !this.paired.foreignIdentifierField) {
      this.paired.foreignIdentifierField = this.through.model.rawAttributes[this.paired.otherKey].field || this.paired.otherKey;
    }

    this.toSource = new BelongsTo(this.through.model, this.source, {
      foreignKey: this.foreignKey
    });
    this.manyFromSource = new HasMany(this.source, this.through.model, {
      foreignKey: this.foreignKey
    });
    this.oneFromSource = new HasOne(this.source, this.through.model, {
      foreignKey: this.foreignKey,
      sourceKey: this.sourceKey,
      as: this.through.model.name
    });

    this.toTarget = new BelongsTo(this.through.model, this.target, {
      foreignKey: this.otherKey
    });
    this.manyFromTarget = new HasMany(this.target, this.through.model, {
      foreignKey: this.otherKey
    });
    this.oneFromTarget = new HasOne(this.target, this.through.model, {
      foreignKey: this.otherKey,
      sourceKey: this.targetKey,
      as: this.through.model.name
    });

    if (this.paired && this.paired.otherKeyDefault) {
      this.paired.toTarget = new BelongsTo(this.paired.through.model, this.paired.target, {
        foreignKey: this.paired.otherKey
      });

      this.paired.oneFromTarget = new HasOne(this.paired.target, this.paired.through.model, {
        foreignKey: this.paired.otherKey,
        sourceKey: this.paired.targetKey,
        as: this.paired.through.model.name
      });
    }

    Helpers.checkNamingCollision(this);

    return this;
  }

  mixin(obj) {
    const methods = ['get', 'count', 'hasSingle', 'hasAll', 'set', 'add', 'addMultiple', 'remove', 'removeMultiple', 'create'];
    const aliases = {
      hasSingle: 'has',
      hasAll: 'has',
      addMultiple: 'add',
      removeMultiple: 'remove'
    };

    Helpers.mixinMethods(this, obj, methods, aliases);
  }

  /**
   * Get everything currently associated with this, using an optional where clause.
   *
   * @see
   * {@link Model} for a full explanation of options
   *
   * @param {Model} instance instance
   * @param {object} [options] find options
   * @param {object} [options.where] An optional where clause to limit the associated models
   * @param {string|boolean} [options.scope] Apply a scope on the related model, or remove its default scope by passing false
   * @param {string} [options.schema] Apply a schema on the related model
   * @param {object} [options.through.where] An optional where clause applied to through model (join table)
   * @param {boolean} [options.through.paranoid=true] If true, only non-deleted records will be returned from the join table. If false, both deleted and non-deleted records will be returned. Only applies if through model is paranoid
   *
   * @returns {Promise<Array<Model>>}
   */
  async get(instance, options) {
    options = Utils.cloneDeep(options) || {};

    const through = this.through;
    let scopeWhere;
    let throughWhere;

    if (this.scope) {
      scopeWhere = { ...this.scope };
    }

    options.where = {
      [Op.and]: [
        scopeWhere,
        options.where
      ]
    };

    if (Object(through.model) === through.model) {
      throughWhere = {};
      throughWhere[this.foreignKey] = instance.get(this.sourceKey);

      if (through.scope) {
        Object.assign(throughWhere, through.scope);
      }

      //If a user pass a where on the options through options, make an "and" with the current throughWhere
      if (options.through && options.through.where) {
        throughWhere = {
          [Op.and]: [throughWhere, options.through.where]
        };
      }

      options.include = options.include || [];
      options.include.push({
        association: this.oneFromTarget,
        attributes: options.joinTableAttributes,
        required: true,
        paranoid: _.get(options.through, 'paranoid', true),
        where: throughWhere
      });
    }

    let model = this.target;
    if (Object.prototype.hasOwnProperty.call(options, 'scope')) {
      if (!options.scope) {
        model = model.unscoped();
      } else {
        model = model.scope(options.scope);
      }
    }

    if (Object.prototype.hasOwnProperty.call(options, 'schema')) {
      model = model.schema(options.schema, options.schemaDelimiter);
    }

    return model.findAll(options);
  }

  /**
   * Count everything currently associated with this, using an optional where clause.
   *
   * @param {Model} instance instance
   * @param {object} [options] find options
   * @param {object} [options.where] An optional where clause to limit the associated models
   * @param {string|boolean} [options.scope] Apply a scope on the related model, or remove its default scope by passing false
   *
   * @returns {Promise<number>}
   */
  async count(instance, options) {
    const sequelize = this.target.sequelize;

    options = Utils.cloneDeep(options);
    options.attributes = [
      [sequelize.fn('COUNT', sequelize.col([this.target.name, this.targetKeyField].join('.'))), 'count']
    ];
    options.joinTableAttributes = [];
    options.raw = true;
    options.plain = true;

    const result = await this.get(instance, options);

    return parseInt(result.count, 10);
  }

  /**
   * Check if one or more instance(s) are associated with this. If a list of instances is passed, the function returns true if _all_ instances are associated
   *
   * @param {Model} sourceInstance source instance to check for an association with
   * @param {Model|Model[]|string[]|string|number[]|number} [instances] Can be an array of instances or their primary keys
   * @param {object} [options] Options passed to getAssociations
   *
   * @returns {Promise<boolean>}
   */
  async has(sourceInstance, instances, options) {
    if (!Array.isArray(instances)) {
      instances = [instances];
    }

    options = {
      raw: true,
      ...options,
      scope: false,
      attributes: [this.targetKey],
      joinTableAttributes: []
    };

    const instancePrimaryKeys = instances.map(instance => {
      if (instance instanceof this.target) {
        return instance.where();
      }
      return {
        [this.targetKey]: instance
      };
    });

    options.where = {
      [Op.and]: [
        { [Op.or]: instancePrimaryKeys },
        options.where
      ]
    };

    const associatedObjects = await this.get(sourceInstance, options);

    return _.differenceWith(instancePrimaryKeys, associatedObjects,
      (a, b) => _.isEqual(a[this.targetKey], b[this.targetKey])).length === 0;
  }

  /**
   * Set the associated models by passing an array of instances or their primary keys.
   * Everything that it not in the passed array will be un-associated.
   *
   * @param {Model} sourceInstance source instance to associate new instances with
   * @param {Model|Model[]|string[]|string|number[]|number} [newAssociatedObjects] A single instance or primary key, or a mixed array of persisted instances or primary keys
   * @param {object} [options] Options passed to `through.findAll`, `bulkCreate`, `update` and `destroy`
   * @param {object} [options.validate] Run validation for the join model
   * @param {object} [options.through] Additional attributes for the join table.
   *
   * @returns {Promise}
   */
  async set(sourceInstance, newAssociatedObjects, options) {
    options = options || {};

    const sourceKey = this.sourceKey;
    const targetKey = this.targetKey;
    const identifier = this.identifier;
    const foreignIdentifier = this.foreignIdentifier;

    if (newAssociatedObjects === null) {
      newAssociatedObjects = [];
    } else {
      newAssociatedObjects = this.toInstanceArray(newAssociatedObjects);
    }
    const where = {
      [identifier]: sourceInstance.get(sourceKey),
      ...this.through.scope
    };

    const updateAssociations = currentRows => {
      const obsoleteAssociations = [];
      const promises = [];
      const defaultAttributes = options.through || {};

      const unassociatedObjects = newAssociatedObjects.filter(obj =>
        !currentRows.some(currentRow => currentRow[foreignIdentifier] === obj.get(targetKey))
      );

      for (const currentRow of currentRows) {
        const newObj = newAssociatedObjects.find(obj => currentRow[foreignIdentifier] === obj.get(targetKey));

        if (!newObj) {
          obsoleteAssociations.push(currentRow);
        } else {
          let throughAttributes = newObj[this.through.model.name];
          // Quick-fix for subtle bug when using existing objects that might have the through model attached (not as an attribute object)
          if (throughAttributes instanceof this.through.model) {
            throughAttributes = {};
          }

          const attributes = { ...defaultAttributes, ...throughAttributes };

          if (Object.keys(attributes).length) {
            promises.push(
              this.through.model.update(attributes, Object.assign(options, {
                where: {
                  [identifier]: sourceInstance.get(sourceKey),
                  [foreignIdentifier]: newObj.get(targetKey)
                }
              }
              ))
            );
          }
        }
      }

      if (obsoleteAssociations.length > 0) {
        promises.push(
          this.through.model.destroy({
            ...options,
            where: {
              [identifier]: sourceInstance.get(sourceKey),
              [foreignIdentifier]: obsoleteAssociations.map(obsoleteAssociation => obsoleteAssociation[foreignIdentifier]),
              ...this.through.scope
            }
          })
        );
      }

      if (unassociatedObjects.length > 0) {
        const bulk = unassociatedObjects.map(unassociatedObject => {
          return {
            ...defaultAttributes,
            ...unassociatedObject[this.through.model.name],
            [identifier]: sourceInstance.get(sourceKey),
            [foreignIdentifier]: unassociatedObject.get(targetKey),
            ...this.through.scope
          };
        });

        promises.push(this.through.model.bulkCreate(bulk, { validate: true, ...options }));
      }

      return Promise.all(promises);
    };

    try {
      const currentRows = await this.through.model.findAll({ ...options, where, raw: true });
      return await updateAssociations(currentRows);
    } catch (error) {
      if (error instanceof EmptyResultError) return updateAssociations([]);
      throw error;
    }
  }

  /**
   * Associate one or several rows with source instance. It will not un-associate any already associated instance
   * that may be missing from `newInstances`.
   *
   * @param {Model} sourceInstance source instance to associate new instances with
   * @param {Model|Model[]|string[]|string|number[]|number} [newInstances] A single instance or primary key, or a mixed array of persisted instances or primary keys
   * @param {object} [options] Options passed to `through.findAll`, `bulkCreate` and `update`
   * @param {object} [options.validate] Run validation for the join model.
   * @param {object} [options.through] Additional attributes for the join table.
   *
   * @returns {Promise}
   */
  async add(sourceInstance, newInstances, options) {
    // If newInstances is null or undefined, no-op
    if (!newInstances) return Promise.resolve();

    options = { ...options };

    const association = this;
    const sourceKey = association.sourceKey;
    const targetKey = association.targetKey;
    const identifier = association.identifier;
    const foreignIdentifier = association.foreignIdentifier;
    const defaultAttributes = options.through || {};

    newInstances = association.toInstanceArray(newInstances);

    const where = {
      [identifier]: sourceInstance.get(sourceKey),
      [foreignIdentifier]: newInstances.map(newInstance => newInstance.get(targetKey)),
      ...association.through.scope
    };

    const updateAssociations = currentRows => {
      const promises = [];
      const unassociatedObjects = [];
      const changedAssociations = [];
      for (const obj of newInstances) {
        const existingAssociation = currentRows && currentRows.find(current => current[foreignIdentifier] === obj.get(targetKey));

        if (!existingAssociation) {
          unassociatedObjects.push(obj);
        } else {
          const throughAttributes = obj[association.through.model.name];
          const attributes = { ...defaultAttributes, ...throughAttributes };

          if (Object.keys(attributes).some(attribute => attributes[attribute] !== existingAssociation[attribute])) {
            changedAssociations.push(obj);
          }
        }
      }

      if (unassociatedObjects.length > 0) {
        const bulk = unassociatedObjects.map(unassociatedObject => {
          const throughAttributes = unassociatedObject[association.through.model.name];
          const attributes = { ...defaultAttributes, ...throughAttributes };

          attributes[identifier] = sourceInstance.get(sourceKey);
          attributes[foreignIdentifier] = unassociatedObject.get(targetKey);

          Object.assign(attributes, association.through.scope);

          return attributes;
        });

        promises.push(association.through.model.bulkCreate(bulk, { validate: true, ...options }));
      }

      for (const assoc of changedAssociations) {
        let throughAttributes = assoc[association.through.model.name];
        const attributes = { ...defaultAttributes, ...throughAttributes };
        // Quick-fix for subtle bug when using existing objects that might have the through model attached (not as an attribute object)
        if (throughAttributes instanceof association.through.model) {
          throughAttributes = {};
        }

        promises.push(association.through.model.update(attributes, Object.assign(options, { where: {
          [identifier]: sourceInstance.get(sourceKey),
          [foreignIdentifier]: assoc.get(targetKey)
        } })));
      }

      return Promise.all(promises);
    };

    try {
      const currentRows = await association.through.model.findAll({ ...options, where, raw: true });
      const [associations] = await updateAssociations(currentRows);
      return associations;
    } catch (error) {
      if (error instanceof EmptyResultError) return updateAssociations();
      throw error;
    }
  }

  /**
   * Un-associate one or more instance(s).
   *
   * @param {Model} sourceInstance instance to un associate instances with
   * @param {Model|Model[]|string|string[]|number|number[]} [oldAssociatedObjects] Can be an Instance or its primary key, or a mixed array of instances and primary keys
   * @param {object} [options] Options passed to `through.destroy`
   *
   * @returns {Promise}
   */
  remove(sourceInstance, oldAssociatedObjects, options) {
    const association = this;

    options = options || {};

    oldAssociatedObjects = association.toInstanceArray(oldAssociatedObjects);

    const where = {
      [association.identifier]: sourceInstance.get(association.sourceKey),
      [association.foreignIdentifier]: oldAssociatedObjects.map(newInstance => newInstance.get(association.targetKey))
    };

    return association.through.model.destroy({ ...options, where });
  }

  /**
   * Create a new instance of the associated model and associate it with this.
   *
   * @param {Model} sourceInstance source instance
   * @param {object} [values] values for target model
   * @param {object} [options] Options passed to create and add
   * @param {object} [options.through] Additional attributes for the join table
   *
   * @returns {Promise}
   */
  async create(sourceInstance, values, options) {
    const association = this;

    options = options || {};
    values = values || {};

    if (Array.isArray(options)) {
      options = {
        fields: options
      };
    }

    if (association.scope) {
      Object.assign(values, association.scope);
      if (options.fields) {
        options.fields = options.fields.concat(Object.keys(association.scope));
      }
    }

    // Create the related model instance
    const newAssociatedObject = await association.target.create(values, options);

    await sourceInstance[association.accessors.add](newAssociatedObject, _.omit(options, ['fields']));
    return newAssociatedObject;
  }

  verifyAssociationAlias(alias) {
    if (typeof alias === 'string') {
      return this.as === alias;
    }

    if (alias && alias.plural) {
      return this.as === alias.plural;
    }

    return !this.isAliased;
  }
}

module.exports = BelongsToMany;
module.exports.BelongsToMany = BelongsToMany;
module.exports.default = BelongsToMany;