timsonner OpenCode Formatters Configuration
Configure and customize code formatters in OpenCode to maintain consistent code styles.
Overview
OpenCode uses language-specific formatters to automatically format files after they are written or edited. This ensures that generated code follows your project's code styles.
How Formatters Work
When OpenCode writes or edits a file, it:
- Checks the file extension against all enabled formatters
- Runs the appropriate formatter command on the file
- Applies the formatting changes automatically
This process happens in the background, ensuring your code styles are maintained without manual steps.
Built-in Formatters
OpenCode comes with several built-in formatters for popular languages and frameworks:
| Formatter | Extensions | Requirements |
|---|---|---|
| air | .R | air command available |
| biome | .js, .jsx, .ts, .tsx, .html, .css, .md, .json, .yaml, and more | biome.json(c) config file |
| cargofmt | .rs | cargo fmt command available |
| clang-format | .c, .cpp, .h, .hpp, .ino, and more | .clang-format config file |
| cljfmt | .clj, .cljs, .cljc, .edn | cljfmt command available |
| dart | .dart | dart command available |
| dfmt | .d | dfmt command available |
| gleam | .gleam | gleam command available |
| gofmt | .go | gofmt command available |
| htmlbeautifier | .erb, .html.erb | htmlbeautifier command available |
| ktlint | .kt, .kts | ktlint command available |
| mix | .ex, .exs, .eex, .heex, .leex, .neex, .sface | mix command available |
| nixfmt | .nix | nixfmt command available |
| ocamlformat | .ml, .mli | ocamlformat command available and .ocamlformat config file |
| ormolu | .hs | ormolu command available |
| oxfmt (Experimental) | .js, .jsx, .ts, .tsx | oxfmt dependency in package.json and experimental env variable flag |
| pint | .php | laravel/pint dependency in composer.json |
| prettier | .js, .jsx, .ts, .tsx, .html, .css, .md, .json, .yaml, and more | prettier dependency in package.json |
| rubocop | .rb, .rake, .gemspec, .ru | rubocop command available |
| ruff | .py, .pyi | ruff command available with config |
| rustfmt | .rs | rustfmt command available |
| shfmt | .sh, .bash | shfmt command available |
| standardrb | .rb, .rake, .gemspec, .ru | standardrb command available |
| terraform | .tf, .tfvars | terraform command available |
| uv | .py, .pyi | uv command available |
| zig | .zig, .zon | zig command available |
If your project has prettier in your package.json, OpenCode will automatically use it for supported file types.
Configuring Formatters
Customize formatters through the formatter section in your OpenCode config (opencode.json):
{
"$schema": "https://opencode.ai/config.json",
"formatter": {}
}
Each formatter configuration supports:
| Property | Type | Description |
|---|---|---|
disabled |
boolean | Set to true to disable the formatter |
command |
string[] | The command to run for formatting |
environment |
object | Environment variables to set when running the formatter |
extensions |
string[] | File extensions this formatter should handle |
Disabling Formatters
To disable all formatters globally:
{
"$schema": "https://opencode.ai/config.json",
"formatter": false
}
To disable a specific formatter:
{
"$schema": "https://opencode.ai/config.json",
"formatter": {
"prettier": {
"disabled": true
}
}
}
Custom Formatters
Override built-in formatters or add new ones:
{
"$schema": "https://opencode.ai/config.json",
"formatter": {
"prettier": {
"command": ["npx", "prettier", "--write", "$FILE"],
"environment": {
"NODE_ENV": "development"
},
"extensions": [".js", ".ts", ".jsx", ".tsx"]
},
"custom-markdown-formatter": {
"command": ["deno", "fmt", "$FILE"],
"extensions": [".md"]
}
}
}
The $FILE placeholder in the command will be replaced with the path to the file being formatted.
Best Practices
- Match Your Project: Ensure formatters match the tools already used in your project
- Team Consistency: Configure formatters to match your team's agreed-upon standards
- Performance: Consider formatter speed, especially for large files
- Reliability: Choose formatters that are actively maintained
- Documentation: Document formatter choices in your project's contribution guidelines
Example Configurations
JavaScript/TypeScript with Prettier
{
"$schema": "https://opencode.ai/config.json",
"formatter": {
"prettier": {
"command": ["npx", "prettier", "--write", "$FILE"],
"extensions": [".js", ".ts", ".jsx", ".tsx", ".vue", ".svelte"]
}
}
}
Rust with Rustfmt
{
"$schema": "https://opencode.ai/config.json",
"formatter": {
"rustfmt": {
"command": ["rustfmt"],
"extensions": [".rs"]
}
}
}
Python with Ruff
{
"$schema": "https://opencode.ai/config.json",
"formatter": {
"ruff": {
"command": ["ruff", "check", "--fix", "$FILE"],
"environment": {},
"extensions": [".py", ".pyi"]
}
}
}
By configuring formatters appropriately, you ensure that OpenCode-generated code maintains consistency with your existing codebase and team standards.