fix: Work with Node.js >=16.12.0

BREAKING CHANGE: Node.js 16.12.0 is required

Fixes #6

index.js

@@ -15,9 +15,9 @@ let nycConfig;
 let testExclude;
 let babelConfig;
 
-export async function transformSource(source, context, defaultTransformSource) {
+export async function load(url, context, nextLoad) {
 	if (context.format !== 'module' || loader.isLoading()) {
-		return defaultTransformSource(source, context, defaultTransformSource);
+		return nextLoad(url, context);
 	}
 
 	if (!nycConfig) {
@@ -41,12 +41,14 @@ export async function transformSource(source, context, defaultTransformSource) {
 		};
 	}
 
-	const filename = fileURLToPath(context.url);
+	const filename = fileURLToPath(url);
 	/* babel-plugin-istanbul does this but the early check optimizes */
 	if (!testExclude.shouldInstrument(filename)) {
-		return defaultTransformSource(source, context, defaultTransformSource);
+		return nextLoad(url, context);
 	}
 
+	const fromNext = await nextLoad(url, context);
+	let {source} = fromNext;
 	if (typeof source !== 'string') {
 		source = new TextDecoder().decode(source);
 	}
@@ -56,7 +58,7 @@ export async function transformSource(source, context, defaultTransformSource) {
 		babelrc: false,
 		configFile: false,
 		filename,
-		/* Revisit this if transformSource adds support for returning sourceMap object */
+		/* Revisit this if the load hook adds support for returning sourceMap object */
 		sourceMaps: babelConfig.produceSourceMap ? 'inline' : false,
 		compact: babelConfig.compact,
 		comments: babelConfig.preserveComments,
@@ -69,5 +71,8 @@ export async function transformSource(source, context, defaultTransformSource) {
 		]
 	});
 
-	return defaultTransformSource(code, context, defaultTransformSource);
+	return {
+		format: fromNext.format,
+		source: code
+	};
 }

package.json

@@ -14,7 +14,7 @@
 		"release": "standard-version"
 	},
 	"engines": {
-		"node": ">=13.7.0"
+		"node": ">=16.12.0"
 	},
 	"license": "ISC",
 	"repository": {

test/index.js

@@ -4,18 +4,19 @@ import {test} from 'libtap';
 import * as loaderHook from '@istanbuljs/esm-loader-hook';
 
 test('exports', async t => {
-	t.same(Object.keys(loaderHook), ['transformSource']);
-	t.match(loaderHook, {transformSource: Function});
+	t.same(Object.keys(loaderHook), ['load']);
+	t.match(loaderHook, {load: Function});
 });
 
 test('transform buffer', async t => {
-	const {source} = await loaderHook.transformSource(
-		Buffer.from('export default true;'),
+	const {source} = await loaderHook.load(
+		new URL('../fixtures/buffer.js', import.meta.url),
 		{
-			format: 'module',
-			url: new URL('../fixtures/buffer.js', import.meta.url)
+			format: 'module'
 		},
-		source => ({source})
+		() => ({
+			source: Buffer.from('export default true;')
+		})
 	);
 
 	t.match(source, /function\s+cov_/u);

test/no-source-maps.js

@@ -1,12 +1,11 @@
 import {test} from 'libtap';
-import {transformSource} from '@istanbuljs/esm-loader-hook';
+import {load} from '@istanbuljs/esm-loader-hook';
 
 test('check transform', async t => {
-	const context = {
-		format: 'module',
-		url: new URL('../fixtures/no-source-map.js', import.meta.url)
-	};
-	const {source} = await transformSource('export default true;', context, source => ({source}));
+	const {source} = await load(
+		new URL('../fixtures/no-source-map.js', import.meta.url),
+		{format: 'module'},
+		() => ({source: 'export default true;'}));
 
 	t.match(source, /function\s+cov_/u);
 	t.match(source, /export\s+default\s+true/u);