This deleted all my source files?

[OmgImAlexis]

So I used yarn as usual to add a new dependancy and from the looks of it all my source that was symlinked via node_modules was removed.

Lucky I had just committed and could use git to retrieve the files but this looks like a huge issue.

PING: @Rush

[OmgImAlexis]

I'm testing but I believe the pre-install script is what would have prevented this.

Maybe there should be more than a small message in the readme about it? Personally I'd suggest having the package check for the preinstall hook and add it unless there's a flag passed.

Something like --no-install?

[Rush]

So I used yarn as usual to add a new dependancy and from the looks of it all my source that was symlinked via node_modules was removed.

Wow, this sounds bad. Can you show me the structure of your project? Btw. just yesterday I discovered that it's possible to link subdirectories via a file: version specifier, is it the way of your project?

[Rush]

Maybe there should be more than a small message in the readme about it? Personally I'd suggest having the package check for the preinstall hook and add it unless there's a flag passed.

Can you elaborate? I am not sure I understand.

link-module-alias shouldn't at any circumstances remove actual source code - this needs to be fixed.

[OmgImAlexis]

Clone this repo and try the steps below. Not sure if this also happens with npm, just wanted to get this to you ASAP.

➜  delete-bug git:(master) rm -rf node_modules
➜  delete-bug git:(master) yarn
yarn install v1.12.3
warning package.json: No license field
warning No license field
[1/4] 🔍  Resolving packages...
[2/4] 🚚  Fetching packages...
[3/4] 🔗  Linking dependencies...
[4/4] 📃  Building fresh packages...

$ link-module-alias
[####################] 20/20link-module-alias: @components -> ./components
✨  Done in 0.80s.
➜  delete-bug git:(master) node main.js
TEST_COMPONENT
➜  delete-bug git:(master) yarn add fuse.js
yarn add v1.12.3
warning package.json: No license field
warning No license field
[1/4] 🔍  Resolving packages...
[2/4] 🚚  Fetching packages...
[3/4] 🔗  Linking dependencies...
[4/4] 📃  Building fresh packages...

warning No license field
success Saved 1 new dependency.
info Direct dependencies
└─ fuse.js@3.3.0
info All dependencies
└─ fuse.js@3.3.0
$ link-module-alias
link-module-alias: @components -> ./components
✨  Done in 0.82s.
➜  delete-bug git:(master) ✗ node main.js
file:///Users/xo/code/delete-bug/index.js:1
Error: Cannot find module '@components'
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:734:10)

[OmgImAlexis]

PING @Rush

[Rush]

@OmgImAlexis I ran your steps - very helpful! .. and it looks like it's a bug in yarn ... I'll investigate it further

[Rush]

@OmgImAlexis it's not a permanent solution but this would help avoid this particular issue:

   "scripts": {
     "preinstall": "which link-module-alias && link-module-alias clean || echo",
     "postinstall": "link-module-alias"
   }

[Rush]

@OmgImAlexis the upstream bug is #5709

I added a comment to that issue thread:
yarnpkg/yarn#5709 (comment)

[Rush]

@OmgImAlexis the thread seems to indicate that another workaround is not using @ in front of the aliased package name.

[josecarneiro]

This happened to me a few times in the last week and it took me a while to understand that using yarn with link-module-alias was the cause of the issue. I haven't been able to reproduce it consistently, it will just happen once in a while. @Rush Is this issue only fixable on yarn's side?

[OmgImAlexis]

@josecarneiro this patch does fix the issue.

#3 (comment)

[josecarneiro]

@josecarneiro this patch does fix the issue.

#3 (comment)

I added it to my package.json and haven't been able to reproduce the issue ever since, so it seems like a plausible solution until yarn solves the underlying problem.

Thank you @OmgImAlexis and @Rush!

[josecarneiro]

Well, it did happen again after running yarn upgrade, even with the fix. It appears that the upgrade command does not run the preinstall hook. Just a heads up for anyone who may be encountering the same issue.

[OmgImAlexis]

This looks related. Possibly a bug?

yarnpkg/yarn#2878