Add the ability to discard history more flexibly

[hanselabreu]

Currently the only way to discard history is via the historic tag. One problem with this approach is that sometimes you do not have control over the update being sent to the editor, thus making it impossible to append any tags to the change.

My proposal is to allow a discardHistory option to be passed to registerHistory which allows a more dynamic way to prevent history from being pushed.

Example below:
https://github.com/facebook/lexical/assets/27902567/1cacdc9a-0dec-4244-80c5-9f2c30361e4e

[vercel]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

Name	Status	Preview	Comments	Updated (UTC)
lexical	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Mar 30, 2024 2:31am
lexical-playground	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Mar 30, 2024 2:31am

[facebook-github-bot]

Hi @hanselabreu!

Thank you for your pull request and welcome to our community.

Action Required

In order to merge any pull request (code, docs, etc.), we require contributors to sign our Contributor License Agreement, and we don't seem to have one on file for you.

Process

In order for us to review and merge your suggested changes, please sign at https://code.facebook.com/cla. If you are contributing on behalf of someone else (eg your employer), the individual CLA may not be sufficient and your employer may need to sign the corporate CLA.

Once the CLA is signed, our tooling will perform checks and validations. Afterwards, the pull request will be tagged with CLA signed. The tagging process may take up to 1 hour after signing. Please give it that time before contacting us about it.

If you have received this in error or have any questions, please contact us at [email protected]. Thanks!

[etrepum]

I don't think you need a PR to do this, I haven't tested this or thought too much about what the current or redoStack should be but something along these lines ought to work

import { useState, useRef } from 'react';
import {createEmptyHistoryState, HistoryPlugin} from '@lexical/history';

export default function DiscardHistoryPlugin({ discard = false }: { discard: boolean }) {
  const [history, setHistory] = useState(createEmptyHistoryState);
  const historyRef = useRef(history);
  useEffect(() => {
    if (discard) {
      // save a copy of the history from before discard=true
      historyRef.current = {...history};
    } else {
      // restore the history redoStack & undoStack unless the initial state was discard=false
      setHistory((curHistory) => curHistory === historyRef.current ? curHistory : { ...historyRef.current, current: curHistory.current });
    }
  }, [discard]);
  return (<HistoryPlugin history={history} />);
}

[hanselabreu]

I don't think you need a PR to do this, I haven't tested this or thought too much about what the current or redoStack should be but something along these lines ought to work

import { useState, useRef } from 'react';
import {createEmptyHistoryState, HistoryPlugin} from '@lexical/history';

export default function DiscardHistoryPlugin({ discard = false }: { discard: boolean }) {
  const [history, setHistory] = useState(createEmptyHistoryState);
  const historyRef = useRef(history);
  useEffect(() => {
    if (discard) {
      // save a copy of the history from before discard=true
      historyRef.current = {...history};
    } else {
      // restore the history redoStack & undoStack unless the initial state was discard=false
      setHistory((curHistory) => curHistory === historyRef.current ? curHistory : { ...historyRef.current, current: curHistory.current });
    }
  }, [discard]);
  return (<HistoryPlugin history={history} />);
}

Honestly, not sure I follow you here. That snippet is not accomplishing the goal of this PR. Also, it should probably trigger an infinite loop once you pass history as a dependency.

The problem is that there is no way to intercept editor changes when discard = true to prevent them from being pushed to the undoStack.

[hanselabreu]

Got the discardHistory name from here.

[facebook-github-bot]

Thank you for signing our Contributor License Agreement. We can now accept your code for this (and any) Meta Open Source project. Thanks!