build: configure Oxfmt and contributor formatting commands

Author: eitsupi

.oxfmtrc.jsonc

@@ -0,0 +1,14 @@
+{
+  "$schema": "./node_modules/oxfmt/configuration_schema.json",
+  "printWidth": 100,
+  "tabWidth": 4,
+  "singleQuote": true,
+  "endOfLine": "lf",
+  // Keep imports and package metadata in their existing order.
+  "sortImports": false,
+  "sortPackageJson": false,
+  // Format TypeScript files only for now: ignore everything, then re-include
+  // directories and TypeScript sources. The CLI and the Oxc VS Code extension
+  // both read this file.
+  "ignorePatterns": ["*", "!*/", "!*.ts", "!*.tsx", "!*.mts", "!*.cts"],
+}

.vscode/settings.json

@@ -7,6 +7,10 @@
         "out": true // set this to false to include "out" folder in search results
     },
     "r.lsp.diagnostics": true,
+    "[typescript][typescriptreact]": {
+        "editor.defaultFormatter": "oxc.oxc-vscode",
+        "editor.formatOnSave": true
+    },
     "editor.codeActionsOnSave": {
         "source.fixAll.markdownlint": "explicit"
     }

CONTRIBUTING.md

@@ -25,6 +25,24 @@ If launching reports `Configured debug type 'extensionHost' is not supported`, e
 
 On VS Code 1.139, the regression can leave the development host paused before any extension activates; the launching window's extension host log shows `ECONNREFUSED ::1` and `Could not find any debuggable target`. Upgrade to VS Code 1.140.0 or newer, or use Microsoft's [JavaScript Debugger Nightly](https://marketplace.visualstudio.com/items?itemName=ms-vscode.js-debug-nightly) as a temporary workaround: disable the built-in **JavaScript Debugger**, enable Nightly, and reload VS Code.
 
+## Formatting and linting
+
+Run `pnpm run format` to format TypeScript files with Oxfmt, and
+`pnpm run format:check` to check formatting without changing files. CI runs the
+same check for pull requests and pushes to `main`. Formatting currently applies
+to TypeScript files only (`.ts`, `.tsx`, `.mts`, and `.cts`); other file types,
+including JavaScript, JSON, Markdown, YAML, R, C, and EJS files, are not formatted.
+
+The checked-in `.oxfmtrc.jsonc` is shared by the CLI and the recommended Oxc
+VS Code extension, and its `ignorePatterns` restrict both to TypeScript files.
+TypeScript files use four-space indentation and single quotes. Import and
+`package.json` sorting are disabled. Oxfmt respects the repository's `.gitignore`
+files, so generated bundles, compiled tests, and dependencies are excluded.
+
+Workspace settings select Oxc as the formatter and enable format on save for
+TypeScript. Run `pnpm run lint` and `pnpm run typecheck` separately to check
+TypeScript code.
+
 ## Building bundled sess
 
 Builds require Git and a checkout with HEAD. `scripts/prepare-sess.js` fingerprints

package.json

@@ -2604,6 +2604,8 @@
     "test:node": "mocha \"out/test/node/**/*.test.js\" --config .mocharc.interactive.cjs",
     "test:extension": "vscode-test",
     "lint": "oxlint src",
+    "format": "oxfmt .",
+    "format:check": "oxfmt --check .",
     "typecheck": "tsc --noEmit -p ./",
     "test:sess-identity": "Rscript --vanilla R/tests/sess_source.R",
     "test:sess-attach": "Rscript --vanilla R/tests/attach_sess.R",
@@ -2627,6 +2629,7 @@
     "glob": "^13.0.6",
     "mocha": "^11.7.5",
     "ovsx": "^0.10.8",
+    "oxfmt": "0.73.0",
     "sinon": "^15.2.0",
     "typescript": "~7.0.2",
     "oxlint": "^1.86.0",