[Checkbox] Fix regression when disabled

[AndrewMusgrave]

WHY are these changes introduced?

It’s unfortunate that we missed this in the build-consumer test. This seems to be a regression caused by not fully understanding #1363. In #1369 I made it so Checkbox cannot be disabled and checked. however, it seems we wanted to remove the ability to fire click events while disabled and keep the ability to change Checkbox checked state.

WHAT is this pull request doing?

• removing unnecessary code
• moving logic from Choice to Checkbox
• updating tests

How to 🎩

• Simple playground to toggle checked and disabled states ⬇️&
• Build-consumer and check the failing test in web

Copy-paste this code in playground/Playground.tsx:

import * as React from 'react';
import {Checkbox, Button} from '@shopify/polaris';

interface State {
  checked: boolean;
  disabled: boolean;
}

export default class Playground extends React.Component {
  state = {
    checked: true,
    disabled: false,
  };

  render() {
    const {checked, disabled} = this.state;

    return (
      <div>
        <Checkbox
          checked={checked}
          disabled={disabled}
          label="Basic checkbox"
          onChange={this.handleChange}
        />
        <Button
          onClick={() => this.setState(({disabled}) => ({disabled: !disabled}))}
        >
          toggle disabled
        </Button>
        <Button
          onClick={() => this.setState(({checked}) => ({checked: !checked}))}
        >
          toggle checked
        </Button>
      </div>
    );
  }

  handleChange = (value) => {
    this.setState({checked: value});
  };
}

[AndrewMusgrave]

This is the logic that caused the regression -> componentDidMount/Update

[AndrewMusgrave]

Added this test to prevent regression in the future

[AndrewMusgrave]

I feel like this logic is out of scope for the Choice component, so it was moved to the handleInput function in Checkbox

[AndrewMusgrave]

@danrosenthal If this looks good to you and the logic makes sense / 🎩 / review are ✅ , feel free to merge this so you can release a patch

[danrosenthal]

Changes and code coverage look great.

This fixes the test failure in web and my 🎩 confirms it also fixes the associated UI regression.