Parcel: HMR with multiple entry points, resulting JS is broken

[kirkone]

🐛 bug report

If multiple entry points or globing ist used with watch or serve when HMR is enabled the compiled js is broken.

🎛 What I used:

parcel watch src/app.ts src/app.scss
parcel watch src/*

🤔 Expected Behavior

The resulting js should not be broken.

😯 Current Behavior

The js file generated has multiple errors an is not working. Also the code from my app.ts is missing.
If I use an index.html as entry point all works fine but I have an additional html file that is not needed.

I also tried to use a glob like this src/* but with the same result.

💁 Possible Solution

I have no idea.

🔦 Context

I only want to use parcel only for js and css without any html. I use it to generate files for an asp.net core site

💻 Code Sample

tbd

🌍 Your Environment

| Software | Version(s) |
| ---------------- | ---------- |
| Parcel | 1.12.4 |
| Node | 12.16.1 |
| npm/Yarn | 6.13.4 |
| Operating System | Windows 10 |

[mischnic]

It sounds like two processes are writing to the same file concurrently and corrupting it..

[kirkone]

I have no idea where to look for a solution but if I can help in any way please give me a hint.

[rndD]

I have the same issue, parcel v1.12.4.

Only if I have multiple entrys

[rndD]

Ok, as a workaround you can turn off HMR: watch somefiles/* --no-hmr

[marcandre]

I can confirm the same bug, happening systematically for me, and --no-hmr indeed fixes the issue.

Probably easy to reproduce, but just in case:
1) checkout repo https://github.com/marcandre/np
2) git reset --hard parcelbug
4) cd lib/np/app && yarn && parcel watch assets/index.* --global App --no-cache
Open the newly created dist/index.js file. Locate line with Kludge; that line ends abruptly and is merged with extra code.

Adding --no-hmr option, or changing index.* to index.js does not create the issue.

As a complete newb' to parcel, this was quite frustrating and difficult to understand.

$ parcel info

Environment Info:

  System:
    OS: macOS High Sierra 10.13.6
    CPU: (12) x64 Intel(R) Xeon(R) CPU           W3670  @ 3.20GHz
  Binaries:
    Node: 14.10.1 - /usr/local/bin/node
    Yarn: 1.22.5 - /usr/local/bin/yarn
    npm: 6.14.8 - /usr/local/bin/npm
  Browsers:
    Chrome: 85.0.4183.102
    Firefox: 80.0.1
    Safari: 13.1.2