Generated JavaScript file references imports that are not in the importmap #10252
Description
🤔 Expected Behavior
The JavaScript does not reference undefined imports.
😯 Current Behavior
The JavaScript fails to load as it tries to import from react/jsx-dev-runtime which isn't defined in the import map.
Uncaught TypeError: Failed to resolve module specifier "react/jsx-dev-runtime". Relative references must start with either "/", "./", or "../".
🔦 Context
In my larger code base, I do use lazy-loading. As far as I can tell, that is intended to create an importmap, but that importmap is missing the entries like those found in this issue. In this issue, there is no import map at all.
💻 Code Sample
package.json
{
"name": "parcel-repro",
"version": "0.0.1",
"dependencies": {
"react": "19.2.3",
"react-dom": "19.2.3"
},
"devDependencies": {
"parcel": "2.16.3"
},
"engines": {
"node": "24.12.0",
"pnpm": "10.27.0"
}
}index.html
<!DOCTYPE html>
<html lang="en">
<head>
<script type="module" src="index.jsx"></script>
</head>
<main>
<body>
<div id="target"></div>
</body>
</main>
</html>index.jsx
import { createRoot } from 'react-dom/client';
const container = document.getElementById('target');
if (container) {
const root = createRoot(container);
root.render(
<span>Hi</span>,
);
}Build the code
pnpm parcel index.html
Visit the site
Visit the dev server in a browser and see that there's a blank page and an error in the console.
You can also look at dist/*.js which starts with the undefined imports:
import * as __parcelExternal0 from "react/jsx-dev-runtime";
import * as __parcelExternal1 from "react-dom/client";index.html does not define an importmap:
<!DOCTYPE html>
<html lang="en">
<head>
<script type="module" src="/repro-clean.4667dcba.js"></script>
</head>
<body>
<main>
<div id="target"></div>
</main>
</body>
</html>🌍 Your Environment
| Software | Version(s) |
|---|---|
| Parcel | 2.16.3 |
| Node | 24.12.0 |
| pnpm | 10.27.0 |
| Operating System | macOS 26.1 (25B78) |
| Browser | Chome Version 145.0.7618.0 (Official Build) canary (arm64) |