chore: use rolldown for building and testing (#360)

1. Replace `tsup` with `tsdown`.
- The tsdown config needs `fixedExtensions` off so that `.js` files are
generated instead of `.mjs`.
2. Replace `vite` with `rolldown-vite`.
    - Override so `vitest` uses it too.
3. Use import attributes when importing `package.json` in `index.ts`,
since tsdown seems to correctly inline only the desired values instead
of the entire file contents.

Author: JasonWeinzierl

AGENTS.md

@@ -20,7 +20,7 @@ The plugin provides 40+ rules that help developers avoid common pitfalls, memory
 - **TypeScript**: Full TypeScript support with strict type checking
 - **RxJS**: Target library for reactive programming patterns
 - **Vitest**: Modern testing framework for unit tests
-- **tsup**: Build tool for dual ESM/CommonJS output
+- **tsdown**: Build tool using modern Rolldown
 
 ## Historical Context
 
@@ -60,7 +60,7 @@ eslint-plugin-rxjs-x/
 ├── LICENSE
 ├── package.json
 ├── README.md
-├── tsup.config.ts          # Build configuration
+├── tsdown.config.ts        # Build configuration
 ├── vitest.config.mts       # Test configuration
 └── yarn.lock               # Packages lockfile
 ```

package.json

@@ -40,7 +40,7 @@
     "dist"
   ],
   "scripts": {
-    "build": "tsup",
+    "build": "tsdown",
     "lint": "yarn lint-js && yarn lint-docs && yarn lint-eslint-docs",
     "lint-js": "eslint",
     "lint-docs": "markdownlint-cli2 \"**/*.md\" \"#node_modules\"",
@@ -88,12 +88,15 @@
     "eslint-plugin-n": "^17.23.2",
     "markdownlint-cli2": "~0.19.0",
     "rxjs": "^7.8.2",
-    "tsup": "8.5.1",
+    "tsdown": "^0.20.3",
     "typescript": "~5.9.3",
     "typescript-eslint": "^8.56.0",
-    "vite": "^7.3.1",
+    "vite": "npm:rolldown-vite@~7.3.1",
     "vitest": "^4.0.18"
   },
+  "resolutions": {
+    "vite": "npm:rolldown-vite@~7.3.1"
+  },
   "engines": {
     "node": "^20.19.0 || ^22.13.0 || >=24"
   }

src/index.ts

@@ -1,6 +1,6 @@
 import type { TSESLint } from '@typescript-eslint/utils';
 import type { ESLint, Rule } from 'eslint';
-import { name, version } from '../package.json';
+import packageJson from '../package.json' with { type: 'json' };
 import { createRecommendedConfig } from './configs/recommended';
 import { createStrictConfig } from './configs/strict';
 
@@ -98,8 +98,8 @@ const allRules = {
 
 const plugin = {
   meta: {
-    name,
-    version,
+    name: packageJson.name,
+    version: packageJson.version,
     namespace: 'rxjs-x',
   },
   /** Compatibility with `defineConfig` until https://github.com/typescript-eslint/typescript-eslint/issues/11543 is addressed. */

tsconfig.json

@@ -16,8 +16,8 @@
     /* Output */
     "noEmit": true,
     "declaration": true,
-    "declarationMap": true,
-    "sourceMap": true,
+    "declarationMap": false,
+    "sourceMap": false,
     "importHelpers": true,
 
     /* Rules */

tsdown.config.ts

@@ -0,0 +1,5 @@
+import { defineConfig } from 'tsdown';
+
+export default defineConfig({
+  fixedExtension: false,
+});