feat(userEvent): Add paste API (fixes #640)

[nickmccurdy]

Migrated from testing-library/user-event#343

What: Add paste API (fixes #640)

Why: The allAtOnce option of type doesn't represent real user interaction intuitively, and we need to fire paste events with the relevant clipboardData

How:

• Extract paste event from old code for type's allAtOnce option
• Implement clipboardData support Support clipboardData like dataTransfer. #585
• Add events
  • paste with clipboardData
  • input with matching value
  • focus
• DataTransfer mock objects

Checklist:

• Documentation added to the
  docs site N/A
• Tests
• Typescript definitions updated N/A
• Ready to be merged
  

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[kentcdodds]

I left some comments, but I just had a thought... What if instead we make a {paste} modifier inside type? This would simplify the implemention quite a bit and honestly makes plenty of sense as an API to me personally.

[nickmccurdy]

What if instead we make a {paste} modifier inside type? This would simplify the implemention quite a bit and honestly makes plenty of sense as an API to me personally.

Shouldn't the typing modifiers be primarily for individual key presses and modifiers? I feel like pasting has different enough responsibilities from typing semantically to be a separate function, just like how clear and tab are functions rather than modifiers. Either way, I'm interested if we could maybe make paste use type more directly to simplify the architecture, as I originally though that wouldn't be possible after removing the allAtOnce option.

[kentcdodds]

Shouldn't the typing modifiers be primarily for individual key presses and modifiers?

Not really. We already have {selectall}. I think type is for anything that the user would do with their keyboard which we feel they do enough to justify having a feature for it. I think it would be reasonable to support {paste} and also have a shortcut userEvent.paste which simply calls into it (similar in some ways to userEvent.clear.

[nickmccurdy]

It still feels like a different kind of user interaction to me. At least {selectall} is directly related to editing some existing text, but users often paste without typing anything else, and as far as I understand this would be the only command that would input many characters immediately.

[kentcdodds]

Fair point 👍 ok, let's proceed with sharing code instead.

[kentcdodds]

Ok, because of the decision to not merge user-event right now, I've back-ported all my improvements to user-event into testing-library/user-event#348, and I included this as well. I hope you don't mind 😬

Thanks!

[nickmccurdy]

This wasn't ready to release, can we revert it?

[kentcdodds]

I made it ready 😁

[nickmccurdy]

Tracking followup work back in testing-library/user-event#355