MoonDiff — Text Diff & Patch Library for MoonBit

Overview

MoonDiff is a text diff & patch library written in MoonBit, created for the MoonBit Ecosystem Open Source Competition (MGPIC 2026).

Zero dependencies, fully generic — any type satisfying Eq can be compared directly. From the classic LCS to Myers’ minimal edit script, from unified patch replay to 3-way merge, and on to RFC 6902 JSON Patch and multi-file tree diff, it’s all in one package.

Installation

moon add yuzhiblue/moon-diff@0.2.2

import yuzhiblue/moon-diff/diff

Features

• 5 diff algorithms: classic LCS, Myers O(ND), Patience diff, Histogram diff, and linear-space Hirschberg (only O(n+m) memory)
• Unified diff: to_unified produces GNU diff -u style output compatible with the standard patch tool; to_unified_stat produces git diff --stat style summaries
• Patch application: exact apply, fuzzy apply (with offset/fuzz tolerance), reverse apply (like patch -R), and +/- flipping
• Git-style: git_diff_text, Git blob SHA-1 hashing, binary diff — with a self-implemented SHA-1
• 3-way merge: diff3-style conflict markers, with ours / theirs resolution strategies
• Semantic JSON diff: emits RFC 6902 JSON Patch (key-order independent), with patch application
• Multi-file tree diff: directory-level diff and patch application with rename detection
• Inline highlighting: word_diff_html produces <del>/<ins> inline comparisons; Unicode-aware tokenization compares CJK text character by character
• Similarity ratio: ratio(a, b) returns a [0,1] similarity score, similar to Python’s difflib.ratio

Quick Start

let a = ["apple", "banana", "cherry"]
let b = ["apple", "blueberry", "cherry"]

let changes = diff(a, b)
// [Equal("apple"), Delete("banana"), Insert("blueberry"), Equal("cherry")]

// unified diff rendering + patch replay
let patch = to_unified(diff_lines(old_text, new_text), "old.txt", "new.txt", 3)
let result = apply_unified(old_text, patch)  // result == new_text

A CLI is included so you can try every capability — diff, patch, merge, json, ratio and more:

moon run cli -- diff "line1\nline2" "line1\nLINE2" --stat
moon run cli -- merge "base" "ours" "theirs" --ours
moon run cli -- ratio "我爱北京" "我爱南京"

Links

• GitHub repository: https://github.com/yuzhiblue/moon-diff
• mooncakes package page: https://mooncakes.io/package/yuzhiblue/moon-diff
• Online API docs: https://mooncakes.io/docs/yuzhiblue/moon-diff@0.2.2

License

Apache-2.0