Should interfaces and their properties be implicitly readonly?

[ghost]

With the readonly-keyword rule, Interfaces throw errors if their properties don't have the keyword. Should interfaces and their properties be implicitly readonly?

// Error
export interface IUserAuthenticationResponse {
  result: boolean;
  data: any;
  errors: any[];
}

// Happy
export interface IUserAuthenticationResponse {
  readonly result: boolean;
  readonly data: any;
  readonly errors: any[];
}

// Error
readonly export interface IUserAuthenticationResponse {
  result: boolean;
  data: any;
  errors: any[];
}

[jonaskello]

I don't think you can put the readonly modifier directly on an interface like that?

If I compile your last example I get this:

error TS1024: 'readonly' modifier can only appear on a property declaration or index signature.

[ghost]

Right, but that's what I'm asking. Should that be the case? When are people mutating interfaces? They aren't instantiated by other instances. They're just adhered to within typed entities.

[jonaskello]

Sure, if you ask me interfaces (and everything else) should be immutable by default in typescript :-).

However if I understand what you are asking correctly this is nothing we can change within the scope of tslint-immutable. Perhaps this discussion should be moved to the typescript repo? Or do you have some action in mind that fits within the scope of this repo?

[jonaskello]

I'm closing this as I cannot see any action we can take but feel free to continue with the discussion.

[ghost]

If anyone stumbles upon this, an ignore-interface option has been added to the readonly-keyword rule. https://github.com/jonaskello/tslint-immutable#using-the-ignore-interface-option