Dynamic Typescript import can only be static

[Javarome]

🐛 bug report

When using the dynamic import syntax in Typescript code, only a constant file name can be referenced.
Using a variable does not transpile to correct module resolving.

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

• No specific babel configuration
• package.json:

{
  "name": "vanilla-typescript",
  "main": "index.html",
  "scripts": {
    "start": "parcel index.html --open"
  },
  "dependencies": {},
  "devDependencies": {
    "parcel-bundler": "^1.6.1",
    "typescript": "^4.0.3"
  }
}

• tsconfig.json:

{
  "compilerOptions": {
    "strict": true,
    "module": "esnext",
    "jsx": "preserve",
    "esModuleInterop": true,
    "sourceMap": true,
    "allowJs": true,
    "lib": [
      "dom",
      "esnext"
    ],
    "target": "ES2018",
    "rootDir": "src",
    "moduleResolution": "node"
  }
}

🤔 Expected Behavior

Dynamic import should work the same when using either a constant file name or a variable file name.

😯 Current Behavior

when using import(fileVar) the file is not found as attempted to be loaded as is, without resolution.
This is because that code part is left as is, not transpiled the way as when import("fileConstant").

Uncaught (in promise) TypeError: Failed to fetch dynamically imported module: http://localhost:1234/dir/someTsFile
Promise.then (async)
parcelRequire.src/index.ts../user/User @ index.ts:85
newRequire @ src.f10117fe.js:47
(anonymous) @ src.f10117fe.js:81
(anonymous) @ src.f10117fe.js:120

💁 Possible Solution

The code with a variable should be transpiled the same way as the code with a constant:

const fileVar = "./dir/someTsFile"
require("_bundle_loader")(require.resolve(fileVar)).then(...)

🔦 Context

This allows lazy loading but prevents any real dynamic loading, where the name/path of module to load depends on runtime (from a user choice, typically).

💻 Code Sample

const fileVar = "./dir/someTsFile";
import(fileVar).then(...)

🌍 Your Environment

Software	Version(s)
Parcel	1.12.4
Node	14.8.0
npm/Yarn	6.14.8
Operating System	MacOS 10.15.7

[mischnic]

Duplicate of #125