Comments break source maps in TypeScript

[smoli]

🐛 bug report

I have a simple project with no parcel config using TypeScript and vue. Having a comment in a ts file breaks the sourcemaps and the line mapping is wrong.

Repository that consistently reproduces the behavior: https://github.com/smoli/parcelSourceMapError

• Just run parcel. (npm start)
• Open the webpage
• Click one of the buttons.
• In console, click on the source-location for the "DEBUG!" output
  --> The output is associated with the wrong line number.

Tested on Chrome 97 and Firefox 96

Turning off HMR does not help.

This is so simple to reproduce, I might do something wrong?

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

There is no config, neither for parcel nor for ts.

Find a repository here, that reproduces the problem: https://github.com/smoli/parcelSourceMapError

package.json

{
  "name": "parcelSourceMaps",
  "version": "1.0.0",
  "description": "",
  "scripts": {
    "start": "parcel ./src/index.html",
    "startNoHMR": "parcel ./src/index.html --no-hmr"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "vue": "^3.2.29",
    "vuex": "^4.0.2"
  },
  "devDependencies": {
    "@parcel/transformer-vue": "^2.2.1",
    "parcel": "^2.2.1"
  }
}

🤔 Expected Behavior

Lines given on console output should match the source position where the console-statement was issued. This translates to break points and debugger statements.

😯 Current Behavior

Source lines are offset when comments are present in the file.

💁 Possible Solution

See comment below

🔦 Context

Makes debugging in large projects impossible.

💻 Code Sample

https://github.com/smoli/parcelSourceMapError

🌍 Your Environment

Software	Version(s)
Parcel	2.2.1
Node	16.13.2
npm/Yarn	npm 8.1.2
Operating System	Win10

[smoli]

I found a fix by using

parcel-transformer-tsc-sourcemaps

and setting removeComments: true in tsconfig.json

See branch fixedbyremovingcomments in the demo project.

As I understand it this fix should be preliminary as parcel-transformer-tsc-sourcemaps is preliminary to mitigate #7570

Maybe this gives some more insight into the problem. Seems as if comments might be considered twice when creating the sourcemaps.

Thanks to @iSplasher and @ImpendingDoom28

[eco747]

idem #7655