Rule proposal: no reference to this.isMountedin components

[lencioni]

I've seen some people write code like if (this.isMounted) instead of if (this.isMounted()). It might be nice to have a rule that notices the former and encourages the latter.

Good:

if (this.isMounted()) {
  ...
}

Bad:

if (this.isMounted) {
  ...
}

[glifchits]

It seems like this would be a feature in ESLint, not just this React plugin. Basically this is a warning/error when you reference a function instead of calling it. I tried searching the ESLint docs for it but I couldn't find anything. I don't know much about ESLint but is it even capable of knowing a variable's type? It seems like quite a challenge, esp. when you consider that we are concerned with object methods (eg. this.isMounted), and globals (which are often functions). Now that I think of it, the global config that is available in ESLint makes no distinction as to its type, so it seems quite unlikely that this feature can exist. Am I right?

[lencioni]

Basically this is a warning/error when you reference a function instead of calling it.

A general rule like that might be useful, but I think it would be difficult to implement. This request is specifically for this.isMounted in React components.

[tleunen]

Not sure it's worth to work on that one...

This method is not available on ES6 class components that extend React.Component. It may be removed entirely in a future version of React.
https://facebook.github.io/react/docs/component-api.html#ismounted

[lencioni]

Indeed, it looks like isMounted is going away. facebook/react#5465

Perhaps there should be a rule that prevents the use of it entirely?