add regression test for #38854

test/production/supports-module-resolution-nodenext/pages/index.tsx

@@ -0,0 +1,5 @@
+import helloWorldString from 'pkg/sub-export'
+
+export default function Page() {
+  return <p>{helloWorldString}</p>
+}

test/production/supports-module-resolution-nodenext/pkg/package.json

@@ -0,0 +1,8 @@
+{
+  "name": "pkg",
+  "version": "1.0.0",
+  "type": "module",
+  "exports": {
+    "./sub-export": "./src/some-file.js"
+  }
+}

test/production/supports-module-resolution-nodenext/pkg/src/some-file.d.ts

@@ -0,0 +1,2 @@
+declare const _default: 'Hello, world'
+export default _default

test/production/supports-module-resolution-nodenext/pkg/src/some-file.js

@@ -0,0 +1 @@
+export default 'Hello, world'

test/production/supports-module-resolution-nodenext/supports-moduleresolution-nodenext.test.ts

@@ -0,0 +1,30 @@
+import { createNextDescribe, FileRef } from 'e2e-utils'
+import { join } from 'path'
+
+// regression test suite for https://github.com/vercel/next.js/issues/38854
+createNextDescribe(
+  'Does not override tsconfig during build',
+  {
+    packageJson: { type: 'module' },
+    files: {
+      'tsconfig.json': new FileRef(join(__dirname, 'tsconfig.json')),
+      pages: new FileRef(join(__dirname, 'pages')),
+      pkg: new FileRef(join(__dirname, 'pkg')),
+    },
+    // skipStart: true,
+    dependencies: {
+      typescript: 'latest',
+      '@types/react': 'latest',
+      '@types/node': 'latest',
+      pkg: './pkg',
+    },
+  },
+  ({ next }) => {
+    it('boots and renders without throwing an error', async () => {
+      // dummy test for now - not sure why this is failing on `next build`,
+      // as I can cd into the isolated next install and run `next build`
+      // without issue...
+      await next.render$('/')
+    })
+  }
+)