After upgrading yarn on Windows, bash scripts won't run without hitting Enter

[kaiyoma]

I upgraded from 0.23.3 to 0.24.6 today on my Windows 10 laptop and I'm seeing a problem whenever I run a bash script through yarn. I have several tasks defined in my package.json that look like this:

    ...
    "lesshint": "bash scripts/lesshint.sh",
    "lint": "bash scripts/lint.sh",
    ...

Now when I execute yarn run lint, the system hangs at this point:

$ yarn run lint
yarn run v0.24.6
$ bash scripts/lint.sh

Normally this script finishes in a few moments, but I noticed after the upgrade today that it was stuck after a minute. I checked Task Manager and nothing was happening. In the shell, I hit Enter and suddenly Node.js came to life in Task Manager and the script finished within a few moments.

This problem isn't happening with all of my shell script tasks, but it's happening with the most important ones.

[kaiyoma]

I went back and installed old versions of yarn, upgrading incrementally, until I hit the problem. Version 0.24.3 worked fine, but 0.24.4 has the issue. As mentioned in the original post, 0.24.6 has the issue too. I tried installing the release candidate (0.25.3) and it suffers from the same issue as well.

[kaiyoma]

I think I spoke too quickly; 0.24.1 has this issue too. The problem seems to be a bit non-deterministic, so it can be tricky to tell if the installed yarn is affected. I can't test 0.24.0 (there's no MSI file). Version 0.23.4 seems to be the last good version; I've run all my bash scripts multiple times and everything works fine. If I upgrade from this to 0.24.1 and try running my tests, something will hang until I press Enter.

[genu]

I can confirm this as well on Windows.

[Ant59]

Can also confirm this issue. Scripts do not execute after yarn run x until another input into the Git Bash prompt on Windows.

[johnste]

I have the same issue, 0.24.6, running from powershell or cmd.

[kaiyoma]

Still an issue in 1.0.2.

[BYK]

I tried this on Windows 10 via cmd and wasn't able to replicate. That said I'm using WSL instead of Git bash so may be this is a problem with Git Bash?

[kaiyoma]

I'm not sure who's at fault, but I do know for sure that the problem was introduced in yarn after version 0.23.4. I've downgraded to that version and I can run my scripts again without any issues. For reference, I'm running git 2.13.0 on Windows 10.

[BYK]

The only patch I've found that has the potential to affect yarn run between 0.23.4 and 0.24.0 was 50c5bf0

Would you like to try reverting this, getting a build and see if that's the cause?

[kaiyoma]

It's also possible that a commit between 0.24.0 and 0.24.1 is the culprit. I can't find an MSI for 0.24.0 so I haven't been able to test that version.

[BYK]

It's also possible that a commit between 0.24.0 and 0.24.1 is the culprit.

That one is not possible: v0.24.0...v0.24.1

I think something went wrong when publishing 0.24.0 so they just bumped the version. Anyways, you can clone the repo, do git checkout -b test v0.24.1, git revert 50c5bf0cde3b71d00d889ff09582b2734b1d5423 and then get yourself a build. That said my suspicion is the added "global bin folder" to PATH code there. May be you have a globally installed script named bash or something? Or may be Windows's new WSL bash eecutable is clashing with Git's and yarn uses that one?

[kaiyoma]

I'm still seeing the issue even after reverting that commit.

[BYK]

That's quite weird because there's nothing else touching the script running code between 0.23.4 and 0.24.1: v0.23.4...v0.24.1

Are you absolutely sure this never happens on 0.23.1 and this is not a problem with your specific configuration or system? Are you able to reproduce this on a different system?

[kaiyoma]

The only thing changing on my system is the yarn version and I can repro the results 100% reliably: 0.23.4 and earlier is fine, but anything after that has the issue. I don't think it's specific to me as others have reported the same issue in this thread. Unfortunately, I don't have access to another system right now.

[kaiyoma]

@BYK I finally browsed the link you posted (the list of changes between versions) and there's absolutely a change that would affect this behavior: a45a677

Maybe that's a good place to start debugging?

[kaiyoma]

FYI, there were some interesting comments today on another thread I'm watching that also involves yarn, Windows, and winpty: #2591 (comment)

Maybe that could be helpful for this discussion too?

[kaiyoma]

OMG, the answer was right in front of my face the whole time. So dumb. :-/

The problem is indeed with the commit I posted above. Previous to that change, use_winpty would be set to true for MSYS*|MINGW* shells, which includes Git Bash for Windows. After the change, the environment variable $YARN_FORCE_WINPTY is checked instead, which is clearly false if you don't set it yourself.

I can verify that after adding export YARN_FORCE_WINPTY=1 to my .bashrc and upgrading to Yarn 1.1.0, everything works again! I can run all my shell scripts just like I used to. 🎉

Leaving this issue open so the maintainers can decide if they want to switch around the logic to use winpty by default instead of the opposite.

[BYK]

I think this is addressed by #4577 so closing.