fix #1477 Note exception to chaining find calls

[unclejustin]

Make it clear that when chaining find calls, you can only use DOM selectors.

What kind of change does this PR introduce? (check at least one)

• Bugfix
• Feature
• Code style update
• Refactor
• Build-related changes
• Other, please describe: Docs update

Does this PR introduce a breaking change? (check one)

• Yes
• No

If yes, please describe the impact and migration path for existing applications:

The PR fulfills these requirements:

• It's submitted to the dev branch.
• When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)
• All tests are passing: https://github.com/vuejs/vue-test-utils/blob/dev/.github/CONTRIBUTING.md#development-setup
• [-] New/updated tests are included

If adding a new feature, the PR's description includes:

• [-] A convincing reason for adding this feature (to avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it)

Other information:

[JessicaSachs]

Nice. Thank you. Can you run the formatter for the docs? yarn format

[unclejustin]

Whoops! My bad, thanks @JessicaSachs formatted and pushed.

[lmiller1990]

Why is this the case? I would have thought find returns a wrapper which should let you use find with any kind of selector. Interesting. Good catch. I wonder if we should totally disallow multiple find calls entirely, if it doesn't cover all the cases.

Can you remove the generated dist files? We don't commit those - those are generated when the next version of the package is published to npm (which will be soon with all the PRs that were merged lately).

[Stoom]

I've used multiple find calls in the past to split things up in my testing:

describe('SomeComponent.vue', () => {
  let button;
  beforeEach(() => {
    button = wrapper.find('button-stub');
  });

  it('Should have an icon', () => {
    const icon = button.find('icon-stub');
    expect(icon.exists()).to.be.true;
  });
});

So this is minimal, but if I had multiple tests on the button then it's cleaner for me to do that outside of each it block.

[lmiller1990]

@Stoom good point. Would be good to figure out why this is the case and fix.