What is the best approach for creating a module declaration file for a JavaScript library that uses inheritance methods not compatible with Typescript?

I need help with a module declaration for a 3rd-party JS library that has subclasses which Typescript detects as incompatible overrides of methods from a parent class. One example is:

Base class:

class Entity {
  ...

  /**
  * Test whether a given User has permission to perform some action on this Entity
  * @param {User} user           The User requesting creation
  * @param {string} action       The attempted action
  * @return {boolean}            Does the User have permission?
  */
  can(user, action) {
    ...
  }
}

Subclass:

class User extends Entity {
  ...

  /**
   * Test whether the User is able to perform a certain permission action. Game Master users are always allowed to
   * perform every action, regardless of permissions.
   *
   * @param {string} permission     The action to test
   * @return {boolean}              Does the user have the ability to perform this action?
   */
   can(permission) {
     ...
   }
}

How can I handle overridden methods like this without getting error messages from tsc? Do I need to somehow misrepresent the relationship between Entity and User?

Answer №1

If you want to remove the can property from the base Entity type, you can create a new type that does this and then assign Entity to a variable of that type.

Subsequently, it is possible to create a subclass based on this altered type. However, keep in mind that this approach disrupts polymorphism, just like what the original developer did. It is considered harmful and should be avoided. Instead, take the time to refactor your code properly.

class Entity {
    can(user: string, action: string) {
        console.log(user, action)
    }
}

type PartialEntity = new () => { [P in Exclude<keyof Entity, 'can'>]: Entity[P] }

const EntityNoCan: PartialEntity = Entity;

class User extends EntityNoCan {
    can(permission: number) {
        console.log(permission)
    }
}

Answer №2

Using a // @ts-ignore directive appears to be the most suitable choice in this scenario. The alternative solution mentioned does not seem to work for type declarations.

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