reconcile/examples/website

Reconcile: conflict-free 3-way text merging

diff3 but with automatic conflict resolution.

Reconcile is a Rust and JavaScript (through WebAssembly) library for merging text without user intervention.

use reconcile::{reconcile, BuiltinTokenizer};

let parent = "Merging text is hard!";
let left = "Merging text is easy!";
let right = "With reconcile, merging documents is hard!";

let deconflicted = reconcile(parent, &left.into(), &right.into(), &*BuiltinTokenizer::Word);
assert_eq!(deconflicted.apply().text(), "With reconcile, merging documents is easy!");

Features

• Conflict-free output (no more git conflict markers)
• Support for updating cursor/selection positions
• Pluggable tokenizer
• Full UTF-8 support
• WASM

Motivation

Sometimes documents get edited concurrently by multiple users (or the same user from multiple devices) resulting in divergent changes.

To allow for offline editing, we could use CRDTs or Operational Transformation (OT) to come to a consistent resolution of the competing version. However, this requires capturing all user actions: insertions, deletes, move, copies, and pastes. In some application, this is trivial if the document can only be edited through an editor that's in our control. But this isn't always the case. Users enjoy composable systems that don't lock them in. For example, one of the unique selling points of Obsidian is to provide an editor experience over a folder Markdown files leaving the user free to change their technology of choice on a whim.

This means that files can be edited out-of-channel and the only information a text synchronisation system can know is the current content of each tracked file. This is the same problem as what Git and similar version control systems solve. Although the problem is similar, there's a relevant difference between syncing source code and personal notes: in the case of the former, a semantically incorrect conflict resolution can wreak havoc in a code base, or worse, introduce a correctness bug unnoticed. Text notes are different though, humans are well-equipped to finding the signal in a noisy environment and "bad merges" might result in a clumsy sentence but the reader will likely still understand the gist and can fix it if necessary.

There are domains of human text which are less tolerant of mis-merges: for instance, a two conflicting changes to a contract could result in a term getting negated in different ways from both sides, resulting in a double-negation, thus, unknowingly changing the meaning.

Architecture

Development

Install nvm

• curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.40.1/install.sh | bash
• nvm install 22
• nvm use 22
• Optionally set the system-wide default: nvm alias default 22

Set up Rust

• Install rustup: curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
• cargo install wasm-pack cargo-insta cargo-edit

Publish new version

scripts/bump-version.sh patch