Fix ignorePureComponents when using class expressions.

[dreid]

This allows the use of a React.PureComponent when used in an expression context for prefer-stateless-function with ignorePureComponents.

Example:

const Foo = class extends React.PureComponent {
  render() {
    return <div>{this.props.foo}</div>;
  }
};

[ljharb]

Should this only apply when the react version setting is >= v15.3?

[ljharb]

(also, why use an expression in that example and not class Foo extends …?

[dreid]

(also, why use an expression in that example and not class Foo extends …?

It's just a minimal obviously correct syntax where ignorePureComponents doesn't work right.

This also fixes usages of non-decorator wrapper functions (and maybe export default class extends…?)

In practice this example probably shouldn't be allowed but that should probably be enforced by a more general eslint rule. :)

[dreid]

I'm not sure about the react version setting.

[ljharb]

I'm not super concerned about people on v15.0, 15.1, or 15.2, but someone on v0.14 shouldn't get a pass from using PureComponent.

[dreid]

Sorry, I might be misunderstanding you, are you proposing that ignorePureComponents shouldn't do anything on < 0.15.3? There do not appear to be (but maybe I missed them) any existing version constraints on ignorePureComponents.

If so, should that be done in this PR? It seems like it's a larger change that would require more discussion.

[ljharb]

You're right, since ignorePureComponents is already an option, dealing with versions isn't the job of this PR.

LGTM.

[dreid]

Is there anything else I need to do for this? I noticed there were some conflicts so I resolved them.

This was approved almost a month ago and hasn't been merged so I just wanted to make sure this wasn't waiting on some action from me.