Add new computed-property-getters rule

[jrjohnson]

Adds rule to fix #344

Which has options to never allow getters in computed properties or always require them.

/// GOOD
Ember.Object.extend({
    fullName: computed('firstName', 'lastName', function() {
        //...
    })
});

// BAD
Ember.Object.extend({
    fullName: computed('firstName', 'lastName', {
        get() {
            //...
        }
    })
});

[Turbo87]

#344 discussed making the rule configurable to allow it to be reversed. in that case, calling the rule no-computed-property-getters might be misleading. having the rule without config seems like a good first step to me, but we should ensure that it doesn't have to be renamed if we ever added configuration.

[jrjohnson]

Thanks @Turbo87. I lost track of that requirement. I was able to figure out how to create the options and test them so now this rule supports both.

[jrjohnson]

@Turbo87 just checking in on this to see if there is anything I should change before I completely forget the context.

[Turbo87]

I think the default should be to only allow them if there is also a setter present. don't ask me how to call that option... 😅

[jrjohnson]

As I started working on the docs for a change to add always-with-setter as an option here it strikes me as a strange thing to lint against. A property created like this would throw an error when accessed anyway since there is no way to get it's value.

Ember.Object.extend({
    fullName: computed('firstName', 'lastName', {
        set() {
            //...
        }
    })
});

Am I confused about what your comment is asking for?

[Turbo87]

what I mean is:

// good
Ember.Object.extend({
    fullName: computed('firstName', 'lastName', function() {
        //...
    })
});

// bad
Ember.Object.extend({
    fullName: computed('firstName', 'lastName', {
        get() {
            //...
        }
    })
});

// good
Ember.Object.extend({
    fullName: computed('firstName', 'lastName', {
        get() {
            //...
        },
        set() {
            //...
        }
    })
});

[jrjohnson]

Thanks for the clarification @Turbo87, I've captured that now and updated the default.

[Turbo87]

@jrjohnson it looks like CI is unhappy about the latest change 🤔

[jrjohnson]

Whoops, thanks @Turbo87. Fixed now.

[Turbo87]

👏 nice work!

[Alonski]

Awesome work @jrjohnson Thank you so much

[jrjohnson]

🎉 thanks for all the great feedback.