[rush] Using rush-pnpm to run scripts with regex causes bash error

[akres]

Summary

Running a Ubuntu-24.04 in WSL2, with Bash version 5.2.21

As a part of our build setup, I need to invoke pnpm with parallell and a regex as the script specifier.
Since version 5.166 I am unable to do this, because I am presented with an error from bash.

Repro steps

Repro repository: https://github.com/akres/rush-pnpm-regex-repro, main branch.
It is just an empty init'd rush monorepo with one package.

1. rush install
2. Go to packages/test and run rushx both
   Expected result:
   Both a and b scripts are executed, resulting in something like

Found configuration in /<redacted>/rush-pnpm-regex-repro/rush.json

Rush Multi-Project Build Tool 5.165.0 - Node.js 22.15.0 (LTS)
> "rush-pnpm run --filter test --parallel \"/a|b/\""

Found configuration in /<redacted>/rush-pnpm-regex-repro/rush.json

. a$ echo 'A'
. b$ echo 'B'
. both$ rush-pnpm run --filter test --parallel "/a|b/"
. a: A
. b: B
. b: Done
. a: Done
. both: Found configuration in /<redacted>/rush-pnpm-regex-repro/rush.json
. both: . a$ echo 'A'
. both: . b$ echo 'B'
. both: . a: A
. both: . b: B
. both: . b: Done
. both: . a: Done
. both: Done

Actual result:

Found configuration in /<redacted>/source/rush-pnpm-regex-repro/rush.json

Rush Multi-Project Build Tool 5.169.3 - Node.js 22.15.0 (LTS)
> "rush-pnpm run --filter test --parallel \"/a|b/\""

Found configuration in /<redacted>/source/rush-pnpm-regex-repro/rush.json

/bin/sh: 1: b/: not found
Error: Failed calling rush-pnpm run --filter test --parallel "/a|b/".  Exit code: 127

Details

The last version where this works is 5.165.0. I have looked at the Changelog of rush and I Have noticed one of the changes in 5.166.0 is

• Remove use of the deprecated shell: true option in process spawn operations.
  which sounds related. I haven't yet tried to debug this to pinpoint the exact issue.

Standard questions

Please answer these questions to help us investigate your issue more quickly:

Question	Answer
@microsoft/rush globally installed version?	5.169.3
rushVersion from rush.json?	5.169.3
pnpmVersion from rush.json?	10.10.0
(if pnpm) useWorkspaces from pnpm-config.json?	true
Operating system?	Linux, Ubuntu 24.04 running on WSL 2 Windows 11
Would you consider contributing a PR?	Yes
Node.js version (node -v)?	22.15.0