Dynamic default scopes in sequelize.js

Question

I am building kind of multitenancy using sequelize.js. Technically I need to filter all queries by predefined column and dynamic value of the current context. General idea was to use defaultScope to filter out other contexts, something like:

var context = () => { return "some current context id"; }

connection.define('kid', {
  firstName: Sequelize.STRING,
  photoUrl: Sequelize.STRING,
  context: {
    type: Sequelize.STRING,
    defaultValue: context // this part works, it accepts function
  }
}, {
  defaultScope: {
    where: {
      context: context // this does not work, it does not accept function and values is defined only once
    }
  }
});

However this does not work because defaultScope is defined on the application start.

What is the right way to do this?

Answer 1

The problem is that Sequelize scopes are defined on the model but you need to apply the scope just before the query because that's when you have context such as the user and role.

Here's a slightly modified copy of the scope merge function from Sequelize which you can use in your hooks such as beforeFind()

// Feel free to write a more fp version; mutations stink.
const {assign, assignWith} = require('lodash')
const applyScope = ({scope, options}) => {
    if (!scope) {
        throw new Error('Invalid scope.')
    }

    if (!options) {
        throw new Error('Invalid options.')
    }

    assignWith(options, scope, (objectValue, sourceValue, key) => {
        if (key === 'where') {
            if (Array.isArray(sourceValue)) {
                return sourceValue
            }
            return assign(objectValue || {}, sourceValue)
        }
        else if (['attributes', 'include'].indexOf(key) >= 0
            && Array.isArray(objectValue)
            && Array.isArray(sourceValue)
        ) {
            return objectValue.concat(sourceValue)
        }

        return objectValue ? objectValue : sourceValue
    })
}

In your model:

 {
    hooks: {
        beforeFind(options) {
            // Mutates options...
            applyScope({
                scope: this.options.scopes.user(options.user)
                , options
            })
            return options
        }
    }
    , scopes: {
        user(user) {
            // Set the scope based on user/role.
            return {
                where: {
                    id: user.id
                }
            }
        }
    }
 }

Finally in your query, set an option with the context that you need.

const user = {id: 12, role: 'admin'}
YourModel.findOne({
    attributes: [
        'id'
    ]
    , where: {
        status: 'enabled'
    }
    , user
})

Answer 2

I'm not sure it will help, but you can override a model default scope anytime.

let defaultScope = {
  where: {
    context: ""
  }
};
defaultScope.where.context = context();
model.addScope('defaultScope',defaultScope,{override: true});