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

See the manual to get started.

Demo: Wrapping Expressions

Difftastic understands expression nesting. If you wrap an expression in an if statement, difftastic understands that the inner values are unchanged.

Compare this with git's default diff. It is confused by indentation changes, and doesn't know which closing parenthesis has been added.

Demo: Reflowing Code

Difftastic is robust to code formatting changes. If you change how many items appear on a single line, difftastic will only show you items which have changed.

In git's default diff, it's harder to see that iter and the curly braces are unchanged. It's also harder to see the affected line numbers.

Languages

Difftastic supports the following languages:

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

If a file has an unrecognised extension, difftastic uses a line-oriented diff.

Known Issues

Performance. Difftastic scales relatively poorly on files with a large number of changes, and can use a lot of memory. This might be solved by A* search.

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

Robustness. Difftastic regularly has releases that fix crashes.

Diff accuracy. Some delimiter moves are currently ignored (see #30).

Integration. Difftastic only has limited support for git and mercurial today.

Non-goals

Patch files. If you want to create a patch that you can later apply, use diff. Difftastic ignores whitespace, so its output is lossy. (AST patching is also a hard problem.)

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.