Error: Bundles must have unique names

🐛 bug report

During the migration from v1 to v2, Parcel seems to be unhappy with my bundles and I’m not sure why (nor sure how to fix them).

🎛 Configuration (.babelrc, package.json, cli command)

Not using a .babelrc file but heres’ the code:

v1

  parcel build \
    --public-url "." \
    --out-dir dist \
    $([[ $MINIFY ]] || echo --no-minify) \
    src/browser/register.ts \
    src/browser/serviceWorker.ts \
    src/browser/pages/login.ts \
    src/browser/pages/vscode.ts

v2

  parcel build \
    --public-url "." \
    --dist-dir dist \
    $([[ $MINIFY ]] || echo --no-optimize) \
    src/browser/register.ts \
    src/browser/serviceWorker.ts \
    src/browser/pages/login.ts \
    src/browser/pages/vscode.t

🤔 Expected Behavior

Parcel 2 should bundle the files like Parcel 1 did (assuming the correct changes have been made).

😯 Current Behavior

Parcel is spitting out an error.

🚨 Build failed.
Error: Bundles must have unique names
AssertionError [ERR_ASSERTION]: Bundles must have unique names
    at BundlerRunner.nameBundles (/Users/jp/Dev/code-server/node_modules/@parcel/core/lib/requests/BundleGraphRequest.js:482:23)
    at processTicksAndRejections (internal/process/task_queues.js:95:5)
    at async BundlerRunner.bundle (/Users/jp/Dev/code-server/node_modules/@parcel/core/lib/requests/BundleGraphRequest.js:434:5)
    at async RequestTracker.runRequest (/Users/jp/Dev/code-server/node_modules/@parcel/core/lib/RequestTracker.js:694:20)
    at async Parcel._build (/Users/jp/Dev/code-server/node_modules/@parcel/core/lib/Parcel.js:661:25)
    at async Parcel.run (/Users/jp/Dev/code-server/node_modules/@parcel/core/lib/Parcel.js:510:18)
    at async run (/Users/jp/Dev/code-server/node_modules/parcel/lib/cli.js:367:7)

💁 Possible Solution

We thought it was because we had this line inside register.ts

import "./pages/error.css"
import "./pages/global.css"
import "./pages/login.css"

Sadly removing that did not solve the issue.

🔦 Context

We’re trying to migrate from v1 to v2 because there are vulnerabilities in v1 and fixing them causing v1 to break so we’re in a pickle 😅

💻 Code Sample

We use Parcel to bundle files for code-server (see here).

🌍 Your Environment

Software	Version(s)
Parcel	^2.0.0-beta.3.1
Node	v14.17.0
npm/Yarn	1.22.10
Operating System	macOS Big Sur 11.3

[mischnic]

In case of your reproduction, the problem was this

diff --git package.json package.json
index 7978540..ac50166 100644
--- package.json
+++ package.json
@@ -1,7 +1,6 @@
 {
   "name": "parcel-v2-build-error",
   "version": "1.0.0",
-  "main": "index.js",
   "license": "MIT",
   "scripts": {
     "build": "./build.sh"

The “main” field should only be set if you’re building a library. And in this case all of the entry points passed to Parcel were assigned index.js as output.

Not sure if that is also causing your original problem though

[mischnic]

The reason I tried to reproduce it is that the error message doesn’t really say which bundles are involved. So in that sense, a small repo would be great.

What you could also do is adding a console.log just before the failing assertion: https://github.com/parcel-bundler/parcel/blob/1ba0bd1833d785c1acf6af36e0a1d429f1ce1fb6/packages/core/core/src/requests/BundleGraphRequest.js#L336 and retrieve the bundle names that way.