My Formatter Will Never Be as Fast as Ruff
a year ago
- #zig
- #code-formatting
- #tree-sitter
- The author built a universal code formatter in Zig using tree-sitter, aiming for consistent formatting across multiple languages.
- Initial benchmarks showed promise, but Ruff (a Python formatter) outperformed it significantly on large files.
- Profiling revealed that 79% of the time was spent parsing the AST, not in the formatting logic itself.
- Attempts to optimize tree-sitter (parser reuse, custom allocators, partial parsing) yielded minimal gains.
- Tree-sitter's design requires parsing entire files at once, making it less optimal for formatting compared to specialized parsers like Ruff's.
- Ruff achieves its speed by using a hand-written recursive descent parser optimized for Python and skipping unnecessary AST features.
- Despite the performance gap, the author sees value in tree-sitter's versatility and multi-language support.
- The project currently achieves ~90% compatibility with Black's formatting rules, with plans to reach 100%.