parcel: [v2] bad error message for package.json#main mismatch with html entry point: "Destination name index.js extension does not match bundle type "html"

🐛 bug report

parcel build is broken. if you take the basic index.html/styles.css setup in the readme: https://github.com/parcel-bundler/parcel/tree/v2#getting-started

you can run parcel index.html fine, but when you run parcel build you get the above mentioned error

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

{
  "name": "netlify-drop-demo-site-master",
  "version": "1.0.0",
  "main": "index.js",
  "repository": "https://github.com/sw-yx/netlify-drop-demo-site-master.git",
  "author": "sw-yx <swyx@dontemail.me>",
  "license": "MIT",
  "devDependencies": {
    "parcel": "^2.0.0-alpha.1.1"
  },
  "scripts": {
    "build": "parcel build basic.html"
  },
  "dependencies": {
    "react": "^16.9.0",
    "react-dom": "^16.9.0"
  }
}

🤔 Expected Behavior

it should build

😯 Current Behavior

doesnt build

yarn run v1.17.0
$ /Users/swyx/Downloads/netlify-drop-demo-site-master/node_modules/.bin/parcel build basic.html
🚨 Destination name index.js extension does not match bundle type "html"
    at BundlerRunner.nameBundle (/Users/swyx/Downloads/netlify-drop-demo-site-master/node_modules/
@parcel/core/lib/BundlerRunner.js:137:17)
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

💁 Possible Solution

no idea

🔦 Context

just trying to try out parcel v2

🌍 Your Environment

Software	Version(s)
Parcel	2.0.0-alpha.1.1
Node	10.13
npm/Yarn	6.51/1.17
Operating System	osx latest

About this issue

Original URL
State: closed
Created 5 years ago
Reactions: 10
Comments: 18 (8 by maintainers)

Commits related to this issue

fix: remove main from package.json to avoid build issue Parcel2 uses main as entry point target. But, main requires js when parcel's entry is html. Removing it apparently does the trick. Build worked... — committed to thebrutalcorporation/koala-names by deduced 3 years ago

Most upvoted comments

https://v2.parceljs.org/features/targets/#library-targets:

To make Parcel ignore one of these fields, specify false in the targets field.
{
 "main": "unrelated.js",
 "targets": {
   "main": false
 }
}

+14

mischnic on Sep 22, 2021

I think could be related to your package.json#main. It uses that to define the output files and your entry is an html file, but your main is expected it to output as a js file. Try updating your main to dist/index.html

+14

kwelch on Sep 6, 2019

i see, thanks kyle. yeah… if im specifying my entry point in the cli, i dont expect my package json main to have Any Effect at all… so this feels like a nasty implicit relationship here that isnt documented.

swyxio on Sep 6, 2019

oh wow, just figured out that if you just leave out the “main” field in package.json and run parcel build index.html it WORKS BEAUTIFUULLY we should just recommend that. it also causes https://github.com/parcel-bundler/parcel/issues/3442 btw, because there will be two index.html entries (one from package.json, one from command line)

swyxio on Nov 30, 2019

Based on this feedback and other confusion about this, we’re considering only using main as a target if the entry point is a JS file. This feature was mostly meant for building libraries instead of applications, where you’d want the package.json to point to the built file. For applications, you typically wouldn’t need a main in package.json, but we can ignore it if you do.

devongovett on Sep 6, 2019

We should add a better error message for this…

devongovett on Sep 6, 2019

@sw-yx what do you think of the below error message? Trying to make it as clear as possible.

devongovett on Dec 2, 2019