Taplo: A Fast TOML Formatter & Linter

Introduction

Taplo is used to automatically format and validate project files like pyproject.toml and cog.toml, ensuring consistent structure and preventing syntax errors across the codebase.

Key Benefits:

  • 🚀 High Performance: Built in Rust, Taplo formats TOML files extremely fast.

  • 🛠 Highly Configurable: Supports options like entry alignment, array expansion, and comment alignment.

  • ✅ Formatter + Linter: Formats and validates TOML files.

  • 🧩 Editor Integration: Works with editors through taplo-lsp.

  • 🤖 CI/CD Friendly: Use taplo format to fix and taplo check to enforce formatting in CI.

⚙️ Getting Started

Installation Install Taplo CLI (requires Rust):

just install-taplo

Quick Example Create a sample TOML file and format it:

echo '[table]\nkey = "value"   # Needs formatting' > example.toml
taplo format example.toml
cat example.toml

Expected output will show aligned key/value and comment (based on config).

🚀 Usage

Example Use Case:

During continuous integration (CI), you want to enforce consistent TOML formatting. With taplo check in your CI pipeline, you can automatically reject pull requests that don’t follow the formatting standards, saving time on manual code review for formatting issues.

Format TOML files:

just format-toml

Check TOML formatting (without modifying files):

just check-toml

Run it manually:

just pre-commit-run

🛑 Disabling Taplo

To temporarily skip formatting:

  • Disable specific rules in .taplo.toml:

[formatting]
respect-ignores = true
line-width = 80
indent-width = 4
align-entries = true
align-comments = true
array-auto-expand = true
array-auto-collapse = false
compact-arrays = false
compact-inline-tables = false
newline-style = "LF"

To completely remove Taplo:

  • Delete .taplo.toml

  • Remove Taplo commands from your Justfile

📚 References