[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 <[e-mail]>",
  "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

[kwelch]

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

[mischnic]

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
 }
}