parcel v2 - Error: Got unexpected undefined

🐛 bug report

While testing out parcel v2 I ran into a fatal build error with an internal-looking failure.

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

CLI parcel watch ./src/ui/index.html

package.json

{
  "targets": {
    "browser": {"publicUrl": "/app"}
  }
}

babelrc

module.exports = {
  presets: ['@babel/preset-env'],
  plugins: [['@babel/plugin-transform-react-jsx', {pragma: 'h'}]],
};

🤔 Expected Behavior

It builds the project or provides an error message as to what is wrong with my configuration.

😯 Current Behavior

It fails with an internal undefined error message.

Error: Got unexpected undefined
    at nullthrows (/Users/patrick/Code/OpenSource/lighthouse-ci/node_modules/nullthrows/nullthrows.js:7:15)
    at RequestGraph.removeById (/Users/patrick/Code/OpenSource/lighthouse-ci/node_modules/@parcel/core/lib/Graph.js:188:40)
    at RequestTracker.untrackRequest (/Users/patrick/Code/OpenSource/lighthouse-ci/node_modules/@parcel/core/lib/RequestTracker.js:284:16)
    at AssetGraphBuilder.handleNodeRemovedFromAssetGraph (/Users/patrick/Code/OpenSource/lighthouse-ci/node_modules/@parcel/core/lib/AssetGraphBuilder.js:279:27)
    at AssetGraph.onNodeRemoved (/Users/patrick/Code/OpenSource/lighthouse-ci/node_modules/@parcel/core/lib/AssetGraphBuilder.js:107:35)
    at AssetGraph.removeNode (/Users/patrick/Code/OpenSource/lighthouse-ci/node_modules/@parcel/core/lib/AssetGraph.js:138:32)
    at AssetGraph.removeEdge (/Users/patrick/Code/OpenSource/lighthouse-ci/node_modules/@parcel/core/lib/Graph.js:215:12)
    at AssetGraph.removeNode (/Users/patrick/Code/OpenSource/lighthouse-ci/node_modules/@parcel/core/lib/Graph.js:179:14)
    at AssetGraph.removeNode (/Users/patrick/Code/OpenSource/lighthouse-ci/node_modules/@parcel/core/lib/AssetGraph.js:139:18)
    at AssetGraph.removeEdge (/Users/patrick/Code/OpenSource/lighthouse-ci/node_modules/@parcel/core/lib/Graph.js:215:12)

🔦 Context

Trying to help test out parcel v2 😃

💻 Code Sample

https://github.com/GoogleChrome/lighthouse-ci/tree/parcelv2/packages/server

in repo root, run yarn and then yarn build:watch

🌍 Your Environment

Software	Version(s)
Parcel	2.0.0-alpha.3.2
Node	v10.15.3
npm/Yarn
Operating System	macOS

[jayantbh]

For me, cleaning the cache fixed the issue. 😅

[Cristy94]

I think it was because of the cache, after clearing the cache it builds but now I get this error: This experimental syntax requires enabling the parser plugin: 'classProperties' .

Related: https://github.com/parcel-bundler/parcel/issues/2668 , but the fix mentioned there doesn’t work.