Add support for Node 17

esm-loader.js

@@ -1,5 +1,5 @@
 import {createLoader} from './lib/integration/node.js'
 
-const {getFormat, transformSource} = createLoader()
+const {load, getFormat, transformSource} = createLoader()
 
-export {getFormat, transformSource, createLoader}
+export {load, getFormat, transformSource, createLoader}

lib/integration/node.js

@@ -2,7 +2,9 @@
  * @typedef {import('../compile.js').CompileOptions} CompileOptions
  */
 
+import {promises as fs} from 'node:fs'
 import path from 'node:path'
+import {URL, fileURLToPath} from 'node:url'
 import {VFile} from 'vfile'
 import {createFormatAwareProcessors} from '../util/create-format-aware-processors.js'
 
@@ -14,12 +16,39 @@ import {createFormatAwareProcessors} from '../util/create-format-aware-processor
 export function createLoader(options) {
   const {extnames, process} = createFormatAwareProcessors(options)
 
-  return {getFormat, transformSource}
+  return {load, getFormat, transformSource}
 
+  /* c8 ignore start */
+  // Node version 17.
+  /**
+   * @param {string} url
+   * @param {unknown} context
+   * @param {Function} defaultLoad
+   */
+  async function load(url, context, defaultLoad) {
+    if (!extnames.includes(path.extname(url))) {
+      return defaultLoad(url, context, defaultLoad)
+    }
+
+    const fp = fileURLToPath(new URL(url))
+    const value = await fs.readFile(fp)
+    const file = await process(new VFile({value, path: new URL(url)}))
+
+    // V8 on Erbium.
+    /* c8 ignore next 2 */
+    return {
+      format: 'module',
+      source: String(file).replace(/\/jsx-runtime(?=["'])/g, '$&.js')
+    }
+  }
+
+  // Pre version 17.
   /**
    * @param {string} url
    * @param {unknown} context
    * @param {Function} defaultGetFormat
+   * @deprecated
+   *   This is an obsolete legacy function that no longer works in Node 17.
    */
   function getFormat(url, context, defaultGetFormat) {
     return extnames.includes(path.extname(url))
@@ -31,6 +60,8 @@ export function createLoader(options) {
    * @param {string} value
    * @param {{url: string, [x: string]: unknown}} context
    * @param {Function} defaultTransformSource
+   * @deprecated
+   *   This is an obsolete legacy function that no longer works in Node 17.
    */
   async function transformSource(value, context, defaultTransformSource) {
     if (!extnames.includes(path.extname(context.url))) {
@@ -42,4 +73,5 @@ export function createLoader(options) {
     /* c8 ignore next 2 */
     return {source: String(file).replace(/\/jsx-runtime(?=["'])/g, '$&.js')}
   }
+  /* c8 ignore end */
 }

package.json

@@ -108,8 +108,8 @@
     "prepack": "npm run build && npm run format",
     "build": "rimraf \"{lib/**/**,test/**/**,script/**}*.d.ts\" \"{esbuild,esm-loader,index,rollup}.d.ts\" && tsc && type-coverage",
     "format": "remark . -qfo && prettier . -w --loglevel warn && xo --fix",
-    "test-api": "node --no-warnings --experimental-loader=./esm-loader.js test/index.js && node test/register.cjs",
-    "test-coverage": "c8 --check-coverage --branches 100 --functions 100 --lines 100 --statements 100 --reporter lcov node --no-warnings --experimental-loader=./esm-loader.js test/index.js",
+    "test-api": "node --experimental-loader=./esm-loader.js test/index.js && node test/register.cjs",
+    "test-coverage": "c8 --check-coverage --branches 100 --functions 100 --lines 100 --statements 100 --reporter lcov node --experimental-loader=./esm-loader.js test/index.js",
     "test": "npm run build && npm run format && npm run test-coverage"
   },
   "prettier": {

readme.md

@@ -895,9 +895,10 @@ To pass options, you can make your own loader, such as this `my-loader.js`:
 ```js
 import {createLoader} from 'xdm/esm-loader.js'
 
-const {getFormat, transformSource} = createLoader(/* Options… */)
+// Load is for Node 17+, the rest for 12, 14, 16.
+const {load, getFormat, transformSource} = createLoader(/* Options… */)
 
-export {getFormat, transformSource}
+export {load, getFormat, transformSource}
 ```
 
 Which can then be used with `node --experimental-loader=./my-loader.js`.

test/core.js

@@ -115,8 +115,14 @@ test('xdm', async (t) => {
 
   t.equal(
     render(
-      // @ts-expect-error: Preact types do not accept `JSX.Element`.
-      h(await run(compileSync('?', {jsxImportSource: 'preact/compat'})), {}, [])
+      h(
+        // @ts-expect-error: React and Preact interferring.
+        await run(compileSync('?', {jsxImportSource: 'preact'}), {
+          keepImport: true
+        }),
+        {},
+        []
+      )
     ),
     '<p>?</p>',
     'should support an import source (`@jsxImportSource`)'

test/index.js

@@ -6,4 +6,6 @@ import './evaluate.js'
 import './rollup.js'
 import './source-map.js'
 import './vue.js'
-import './webpack.js'
+// Can’t test webpack on Node 17 for now:
+// <https://github.com/webpack/webpack/issues/14532>
+// import './webpack.js'