mbrukman / difftastic

a diff that understands syntax 🟥🟩

Difftastic is an experimental diff tool that compares files based on their syntax.

For installation instructions, see Getting Started in the manual.

Basic Example

In this JavaScript example, we can see:

(1) Difftastic understands nesting. It highlights the matching { and }, but understands that foo() hasn't changed despite the leading whitespace.

(2) Difftastic understands which lines should be aligned. It's aligned bar() on the left with bar(1) on the right, despite their changes.

(3) Difftastic understands that line-wrapping isn't meaningful. "eric" is now on a new line, but it hasn't changed.

One Minute Demo

This one minute screencast demonstrates difftastic usage with both standalone files and git.

Languages

Difftastic supports the following languages:

• Bash
• C
• C++
• C#
• Clojure
• Common Lisp
• CSS
• Dart
• Elixir
• Emacs Lisp
• Go
• Haskell
• Janet
• Java
• JavaScript (and JSX)
• JSON
• Lua
• Nix
• OCaml
• PHP
• Python
• Ruby
• Rust
• Scala
• TypeScript (and TSX)

If a file has an unrecognised extension, difftastic uses a textual diff with word highlighting.

Known Issues

Performance. Difftastic scales relatively poorly on files with a large number of changes, and can use a lot of memory.

Display. Difftastic has a side-by-side display which usually works well, but can be confusing.

Robustness. Difftastic regularly has releases that fix crashes.

Non-goals

Patching. Difftastic output is intended for human consumption, and it does not generate patches that you can apply later. Use diff if you need a patch.

Merging. AST merging is a hard problem that difftastic does not address.

License

Difftastic is open source under the MIT license, see LICENSE for more details.

Files in sample_files/ are also under the MIT license unless stated otherwise in their header.