How to avoid spurious 'unused parameter' warnings in TypeScript

Question

I've encountered this a bunch and have finally decided to figure out what the right way to do it is. If I have an abstract parent class that declares a method, and then some of the concrete sub-classes implement real logic in their implementation (and, obviously, use the method parameters), but some of the sub-classes don't need to do anything in that method (so don't use the method parameters) - the ones that don't have to do anything generate spurious (in my view) warnings in my code.

For instance, if I have some classes that look like:

abstract class Child {
  constructor(protected name: string) {
    connsole.log(name + " was just born.");
  }

  abstract tellThemToDoSomething(command: string);
}

class GoodChild extends Child {
  constructor(name: string) { super(name); }
  tellThemToDoSomething(command: string) {
    console.log("I will do " + command);
  }
}

class BadChild extends Child {
  constructor(name: string) { super(name); }
  tellThemToDoSomething(command: string) {
    // bad children just ignore what their parents tell them
  }
}

Then I get a (TSLint? JSLint? WebStorm?) warning in WebStorm for the unused parameter in the BadChild tellThemToDoSomethign() method.

I know of a few options, but none seem great.

1) Ignore it (but that seems suboptimal, since I'll grow blind to real warnings)

2) Remove the parameter from the BadChild's method implementation (but that unfortunately removes useful information, since I may later want to implement it, and not having the signature there makes it more difficult, and I also get errors from callers expecting there to be parameters - though given that I should be able to call a method with extraneous parameters in JavaScript, I be there's a way around that problem)

3) Tell WebStorm(TSLint) to stop warning on unused parameters (but that seems suboptimal since I won't get warnings in other real problem situations)

4) Do something meaningless with the parameter so it is not unused (obviously not great)

What is do experienced Java/TypeScript coders do in situations like this? Is there an easy way to tell WebStorm/TSLint to ignore the parameter in individual cases like this? Or, even better, a way to tell it to ignore unused parameters in sub-class implementations of abstract methods, as long as some implementations actually use the parameters?

I'm a little unsure on where the warning is coming from, though, since my brief googling shows a TSLint warning for unused-variables but not unused-parameters, and adding a // tslint:ignore-next-line:no-unused-parameter (or no-unused-variable) didn't make the warning go away. So I guess it's possible the warning is coming from WebStorm itself? Further, the warning is "Unused parameter Foo: Checks JavaScript parameter, local variable, function, classes and private member declarations to be used in given file scope". So it doesn't look like a TSLint warning. And if I look in my WebStorm Preferences -> Languages & Frameworks -> Javascript -> Code Quality Tools, none of the linters are enabled (JSLint, JSHint, ESLint, etc.). So any idea where the error is coming from?

I've not coded in TypeScript long enough to have a feel for what the ideal dial on this warning should be.

You can remove that warning only for the current file. Put this at the beginning of the file. /* tslint:disable:no-unused-variable */ — Kavindra
That would result in masking other (potentially) real warnings, no? — Doug
This disables warnings only for that file. But if you need them in the rest of the file you can put this just before the class BadChild and reenable it just after the class using /* tslint:enable:no-unused-variable */ — Kavindra
That seems like a lot of clumsy commenting. Is that what people really do? Or do they just ignore these kinds of warnings? — Doug
Also - see my recent edit - I'm not sure it's a TSLint warning. — Doug

Estus Flask Estus Flask · Accepted Answer · 2018-05-10T06:33:20

This warning is caused by JetBrains PhpStorm/WebStorm inspections.

A conventional way that is properly handled by TypeScript is to underscore unused parameters. Unfortunately, this convention isn't supported by JetBrains IDEs.

It's possible to suppress inspections in-place in some cases by triggering suggestion list with Alt+Enter/⌥+Enter and choosing Suppress for statement (this never worked for me for IDE inspections).

It's possible to suppress inspections in inspections results.

This results in adding a comment above the method and affects all unused parameters in this method signature:

// noinspection JSUnusedLocalSymbols
tellThemToDoSomething(_command: string) {}

This can be added to live templates, etc.

How to avoid spurious 'unused parameter' warnings in TypeScript

1 Answers