feat: expose CommonJS API via tsx/cjs/api (#3)

docs/node.md

@@ -43,9 +43,81 @@ node --import tsx/esm ./file.ts
 node --loader tsx/esm ./file.ts
 ```
 
-### CommonJS only
-If you only need to add TypeScript & ESM support in a CommonJS context, you can use the CJS loader:
+---
+
+# CommonJS
+
+If you only need to add TypeScript & ESM support in a CommonJS context.
+
+## Command-line API
+
+Pass tsx into the `--require` flag:
 
 ```sh
 node --require tsx/cjs ./file.ts
 ```
+
+## Node.js API
+
+### Globally patching `require`
+
+#### Enabling TSX Enhancement
+
+To enhance the global `require()` function with TypeScript support, prepend your script with the following line:
+
+```js
+require('tsx/cjs')
+```
+
+#### Manual Registration & Unregistration
+
+To manually register and unregister the TypeScript enhancement on the global `require()`:
+
+```js
+const tsx = require('tsx/cjs/api')
+
+// Register tsx enhancement for all global require() calls
+const unregister = tsx.register()
+
+// Optionally, unregister the enhancement when needed
+unregister()
+```
+
+### Isolated `require()`
+
+In situations where TypeScript support is needed only for loading a specific file (e.g. within third-party packages) without affecting the global environment, you can utilize tsx's custom `require` function.
+
+Note the current file path must be passed in as the second argument so it knows how to resolve relative paths.
+
+#### CommonJS usage
+```js
+const tsx = require('tsx/cjs/api')
+
+const loaded = tsx.require('./file.ts', __filename)
+const filepath = tsx.require.resolve('./file.ts', __filename)
+```
+
+#### ESM usage
+```js
+import { require } from 'tsx/cjs/api'
+
+const loaded = require('./file.ts', import.meta.url)
+const filepath = require.resolve('./file.ts', import.meta.url)
+```
+
+#### Module graph
+
+If you're interested in seeing what files were loaded, you can traverse the CommonJS module graph. This can be useful for watchers:
+
+```js
+// To detect watch files, we can parse the CommonJS module graph
+const resolvedPath = require.resolve('./file', import.meta.url)
+
+const collectDependencies = module => [
+    module.filename,
+    ...module.children.flatMap(collectDependencies)
+]
+
+console.log(collectDependencies(require.cache[resolvedPath]))
+// ['/file.ts', '/foo.ts', '/bar.ts']
+```

package.json

@@ -26,6 +26,10 @@
 		"./package.json": "./package.json",
 		".": "./dist/loader.mjs",
 		"./cjs": "./dist/cjs/index.cjs",
+		"./cjs/api": {
+			"types": "./dist/cjs/api/index.d.ts",
+			"default": "./dist/cjs/api/index.cjs"
+		},
 		"./esm": "./dist/esm/index.mjs",
 		"./cli": "./dist/cli.mjs",
 		"./source-map": "./dist/source-map.cjs",

src/cjs/api/index.ts

@@ -1 +1,2 @@
 export { register } from './global-require-patch.js';
+export { require } from './require.js';

src/cjs/api/require.ts

@@ -0,0 +1,48 @@
+import path from 'path';
+import { fileURLToPath } from 'node:url';
+import { register } from './global-require-patch.js';
+import { resolveFilename } from './module-resolve-filename.js';
+
+const getRequestContext = (
+	filepath: string | URL,
+) => {
+	if (
+		(typeof filepath === 'string' && filepath.startsWith('file://'))
+		|| filepath instanceof URL
+	) {
+		filepath = fileURLToPath(filepath);
+	}
+	return path.dirname(filepath);
+};
+
+const tsxRequire = (
+	id: string,
+	fromFile: string | URL,
+) => {
+	const unregister = register();
+	try {
+		const contextId = path.resolve(getRequestContext(fromFile), id);
+
+		// eslint-disable-next-line import-x/no-dynamic-require, n/global-require
+		return require(contextId);
+	} finally {
+		unregister();
+	}
+};
+
+const resolve = (
+	id: string,
+	fromFile: string | URL,
+	options?: { paths?: string[] | undefined },
+) => {
+	const contextId = path.resolve(getRequestContext(fromFile), id);
+	return resolveFilename(contextId, module, false, options);
+};
+resolve.paths = require.resolve.paths;
+
+tsxRequire.resolve = resolve;
+tsxRequire.main = require.main;
+tsxRequire.extensions = require.extensions;
+tsxRequire.cache = require.cache;
+
+export { tsxRequire as require };