[ScopeHoisting] Statically exported members used internally inside the class scope should have exports mapped to module scope when bundled

[Stradivario]

🐛 bug report

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

package.json

{
  "scripts": {
    "start": "parcel start ./src/index.html --public-url=/flags",
    "build": "parcel build ./src/index.html --public-url=/flags --experimental-scope-hoisting"
  },
  "dependencies": {
    "@rxdi/core": "^0.6.7",
    "@rxdi/lit-html": "^0.6.7",
    "rxjs": "^6.5.2",
    "@webcomponents/webcomponentsjs": "^1.2.4",
    "@babel/polyfill": "^7.0.0"
  },
  "browserslist": [
    "last 1 chrome versions"
  ]
}

tsconfig.json

{
  "compileOnSave": false,
  "compilerOptions": {
    "baseUrl": ".",
    "sourceMap": true,
    "module": "esnext",
    "declaration": false,
    "moduleResolution": "node",
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "esModuleInterop": true,
    "target": "es6",
    "typeRoots": [
      "node_modules/@types"
    ],
    "lib": [
      "es2015",
      "es2016",
      "es6",
      "es2017",
      "dom"
    ]
  },
  "include": [
    "./src/**/*"
  ]
}

🤔 Expected Behavior

Statically exported members used internally inside the class scope should have exports mapped to module scope when bundled

😯 Current Behavior

Statically exported members are not mapped internally inside the scope of the current Class which leading to property of undefined

example:

This peace of code is taken from https://github.com/Polymer/lit-html/blob/master/src/lib/parts.ts#L145

Important part is here:
https://github.com/Polymer/lit-html/blob/master/src/lib/parts.ts#L311

They are creating new Instance of the class NodePart as a factory if this particular part doesn't exist inside the DOM.

The problem here is that when compiled this part of code remains the same without export referencing him to the module scope

Typescript

itemPart = new NodePart(this.options);

Javascript

itemPart = new NodePart(this.options);

Instead it should be

itemPart = new exports.NodePart(this.options);

The case here is that i am getting the following error

Uncaught ReferenceError: NodePart is not defined

When i change the code with exports.NodePart everything is back to normal and i can use my application with Scope hoisting.

Is this normal to behave like this ?

Is it a problem with implementation and how Typescript compile the code without exports.NodePart ?

Is this issue for Typescript team or ParcelJS ?

here is a simple repository reproducing the problem

https://github.com/Stradivario/parcel-scope-hoisting

1.Run npm start (to have server started)
2. Run npm run build command
3. Try to refresh the page after build is success
4. You will get the following error Uncaught ReferenceError: NodePart is not defined
5. Then run command npm run fix and wait for build to finish
6. Refresh the page and you will se that the application is working properly

npm run fix

This command copy file with exports.NodePart property to node_modules folder and then rerun parcel build ./src/index.html --public-url=/flags --experimental-scope-hoisting

Why this thing happen ? Anyone ?

🌍 Your Environment

Software	Version(s)
Parcel	1.12.3
Node	10.16.0
npm	6.9.0
Operating System	Ubuntu 18.4.2

[Stradivario]

Pull request with current fix on Polymer lit-html

lit/lit#954

[mischnic]

This is a bug in the renaming process, (and I thought we had it fixed: #2986, #2513, #2981):

class NodePart {
    __commitIterable(value) {
        let x = new NodePart();
    }
}

is turned into

class $zoHw$var$NodePart {
    __commitIterable(value) {
        let x = new NodePart(); // NodePart is undefined now
    }
}

[Stradivario]

@mischnic i am glad that i face it then!

Also getting the same output trying to build this lib

https://github.com/vaadin/vaadin-router/blob/master/src/router.js#L187

They are using Static methods when initializing constructor properties thus leading to the same error

Regards!

[Stradivario]

Any news here guys :) ? @mischnic

[mischnic]

Please follow #3664 for updates