build: change bundler to tsdown

Author: michaelfaith

package.json

@@ -11,7 +11,7 @@
   },
   "license": "MIT",
   "scripts": {
-    "build": "tsup",
+    "build": "tsdown",
     "format": "prettier --write .",
     "format:check": "prettier --check .",
     "lint": "npm-run-all --continue-on-error --aggregate-output --parallel lint:*",
@@ -83,7 +83,7 @@
     "npm-run-all2": "^7.0.1",
     "prettier": "^3.6.2",
     "release-it": "^17.2.0",
-    "tsup": "^8.5.0",
+    "tsdown": "^0.13.3",
     "typescript": "^5.9.2",
     "typescript-eslint": "^8.39.0",
     "vitest": "^3.2.4"

tsconfig.json

@@ -13,6 +13,7 @@
     "verbatimModuleSyntax": true,
     "erasableSyntaxOnly": true,
     "forceConsistentCasingInFileNames": true,
+    "rewriteRelativeImportExtensions": true,
     "paths": {
       "eslint-plugin-eslint-plugin": ["./lib/index.ts"]
     },

tsup.config.ts renamed to tsdown.config.ts

@@ -1,7 +1,7 @@
-import { defineConfig } from 'tsup';
+import { defineConfig } from 'tsdown';
 
 export default defineConfig({
-  bundle: false,
+  unbundle: true,
   clean: true,
   dts: true,
   entry: ['lib/**/*.ts'],