fix: preserve CJS JSON require in ESM hooks

closes #794

Author: privatenumber

src/esm/hook/load.ts

@@ -231,10 +231,10 @@ const prepareJsonAttributes = (
 };
 
 const isCommonJsRequireContext = (
-	context: Parameters<LoadHook>[1],
+	{ conditions }: Parameters<LoadHook>[1],
 ) => (
-	context.conditions.includes('require')
-	&& !context.conditions.includes('import')
+	conditions?.includes('require') === true
+	&& !conditions.includes('import')
 );
 
 export const createLoad = (
@@ -361,6 +361,9 @@ export const createLoad = (
 		}
 
 		const code = loaded.source.toString();
+		// CJS JSON require still parses hook source as JSON after module hooks.
+		// https://github.com/nodejs/node/blob/v24.15.0/lib/internal/modules/cjs/loader.js#L1969-L1978
+		const shouldTransformJson = loadedFormat === 'json' && !isCommonJsRequireContext(context);
 
 		if (loadedFormat === 'commonjs-typescript') {
 			const transformed = transformSync(
@@ -380,7 +383,7 @@ export const createLoad = (
 
 		if (
 			// Support named imports in JSON modules
-			loaded.format === 'json'
+			shouldTransformJson
 			|| isModuleTypeScriptFormat(loadedFormat)
 			|| tsExtensionsPattern.test(url)
 		) {
@@ -509,6 +512,9 @@ export const createLoadSync = (
 		}
 
 		const code = loaded.source.toString();
+		// CJS JSON require still parses hook source as JSON after module hooks.
+		// https://github.com/nodejs/node/blob/v24.15.0/lib/internal/modules/cjs/loader.js#L1969-L1978
+		const shouldTransformJson = loadedFormat === 'json' && !isCommonJsRequireContext(context);
 
 		if (loadedFormat === 'commonjs-typescript') {
 			const transformed = transformSync(
@@ -529,7 +535,7 @@ export const createLoadSync = (
 
 		if (
 			// Support named imports in JSON modules
-			loaded.format === 'json'
+			shouldTransformJson
 			|| isModuleTypeScriptFormat(loadedFormat)
 			|| tsExtensionsPattern.test(url)
 		) {

tests/specs/version-sensitive.ts

@@ -136,6 +136,36 @@ export const versionSensitiveTests = (node: NodeApis) => describe('Version-sensi
 			);
 		});
 
+		test('sync ESM hook preserves CJS JSON require', async () => {
+			await using fixture = await createFixture({
+				'package.json': createPackageJson({ type: 'commonjs' }),
+				'entry.cjs': 'require("fake-mocha/lib/mocha.js");',
+				'node_modules/fake-mocha': {
+					'package.json': createPackageJson({ type: 'commonjs' }),
+					lib: {
+						'mocha.js': `
+							const mocharc = require("./mocharc.json");
+
+							console.log(JSON.stringify(mocharc));
+							`,
+						'mocharc.json': JSON.stringify({
+							diff: true,
+							extension: ['js', 'cjs', 'mjs'],
+						}),
+					},
+				},
+			});
+
+			const process = await node.hook(['entry.cjs'], fixture.path);
+
+			expect(process.exitCode).toBe(0);
+			expect(process.stderr).toBe('');
+			expect(JSON.parse(process.stdout)).toEqual({
+				diff: true,
+				extension: ['js', 'cjs', 'mjs'],
+			});
+		});
+
 		await test('watch reruns when imported TypeScript file changes', async () => {
 			await using fixture = await createFixture({
 				'package.json': createPackageJson({ type: 'commonjs' }),