Add TypeScript loader (#7)

Author: JakobJingleheimer

https-loader/package.json

@@ -3,6 +3,10 @@
   "version": "0.1.0",
   "description": "",
   "type": "module",
+  "exports": {
+    ".": "./loader.js",
+    "./package.json": "./package.json"
+  },
   "scripts": {
     "start": "npm test",
     "test": "node --experimental-loader ./loader.js test.js"

typescript-loader/fixtures/app.ts

@@ -0,0 +1,4 @@
+import { sum, VERSION } from './utils.ts';
+
+console.log('sum:', sum(3,4));
+console.log('VERSION:', VERSION);

typescript-loader/fixtures/index.js

@@ -0,0 +1 @@
+import './app.ts';

typescript-loader/fixtures/utils.ts

@@ -0,0 +1,3 @@
+export { VERSION } from './vendor.js';
+
+export function sum(a: number, b: number) { return a + b }

typescript-loader/fixtures/vendor.js

@@ -0,0 +1 @@
+export const VERSION = 42;

typescript-loader/loader.js

@@ -0,0 +1,46 @@
+// 💡 It's probably a good idea to put this loader near the end of the chain.
+
+import path from 'node:path';
+
+import { transform } from 'esbuild';
+
+
+const tsExts = new Set([
+  '.tsx',
+  '.ts',
+  '.mts',
+  '.cts',
+]);
+
+export async function resolve(specifier, context, nextResolve) {
+  const ext = path.extname(specifier);
+
+  if (!tsExts.has(ext)) { return nextResolve(specifier); } // File is not ts, so step aside
+
+  const { url } = await nextResolve(specifier); // This can be deduplicated but isn't for simplicity
+
+  return {
+    format: 'typescript', // Provide a signal to `load`
+    shortCircuit: true,
+    url,
+  };
+}
+
+export async function load(url, context, nextLoad) {
+  if (context.format !== 'typescript') { return nextLoad(url); }
+
+  const rawSource = '' + (await nextLoad(url, { ...context, format: 'module' })).source;
+
+  const { code: transpiledSource } = await transform(rawSource, {
+    format: 'esm',
+		loader: 'ts',
+		sourcemap: 'inline',
+		target: 'esnext',
+  });
+
+  return {
+    format: 'module',
+    shortCircuit: true,
+    source: transpiledSource,
+  };
+}