Way to tell TS that a JavaScript variable really is used somewhere

[mjbvz]

From microsoft/vscode#51405

Feature request
For JavaScript, add a way to mark that a variable that appears unused is used somewhere. For example it may be used within a template that TS cannot analyze

Not sure if @ts-ignore should suppress unused too. It currently has no effect:

[ghost]

@Fedoranimus A public method should never be marked as unused because unused testing isn't that smart. Similarly, something in global scope should never be marked as unused. We only mark things unused if they have a limited scope (or are private but that's not yet implemented for JS -- #14009). In a local scope I can't come up with an example other than eval where something that doesn't appear to be used, is.

[parzh]

@Andy-MS What about AngularJS? There are cases when you have a variable in the controller, which is used indirectly in the view:

<!-- my-thing.component.html -->
<div>{{ $ctrl.property }}</div>

// my-thing.component.ts
class MyThing {
  public property = 42; // marked as unused, but is really used in the view
}

[ghost]

@parzh Are you sure there isn't some other tool marking that as unused? TypeScript should never mark anything public as unused.

[parzh]

@Andy-MS Oh, I actually didn't test it. Sorry for the confusion 😔
I just meant that there are cases where it might actually be useful to indicate explicitly that a locally scoped entity is used, even if it appears as unused. A lot of those are related to frameworks with view separated from controller (like AngularJS), but unfortunately I gave a bad example.

[ghost]

As far as I can tell, there's no case where unused detection has a false positive (other than something erroneously marked private) -- let me know if you find a counterexample.

[typescript-bot]

Automatically closing this issue for housekeeping purposes. The issue labels indicate that it is unactionable at the moment or has already been addressed.