From 87199460361280e8e8da3952ea2195d41e1fd996 Mon Sep 17 00:00:00 2001
From: Austin Ziegler <austin@zieglers.ca>
Date: Thu, 4 May 2023 10:28:11 -0400
Subject: [PATCH] Allow brew shellenv to accept a shell name param

Resolves #15358

With this change, `brew shellenv` will accept a shell name parameter to
override its default output (based on `/bin/ps`) for advanced use cases
such as with dotfile templating and caching with
[twpayne/chezmoi](https://github.com/twpayne/chezmoi/discussions/2971).
When running under `fish`, this is the output:

```console
$ brew shellenv pwsh
[System.Environment]::SetEnvironmentVariable('HOMEBREW_PREFIX','/opt/homebrew',[System.EnvironmentVariableTarget]::Process)
[System.Environment]::SetEnvironmentVariable('HOMEBREW_CELLAR','/opt/homebrew/Cellar',[System.EnvironmentVariableTarget]::Process)
[System.Environment]::SetEnvironmentVariable('HOMEBREW_REPOSITORY','/opt/homebrew',[System.EnvironmentVariableTarget]::Process)
[System.Environment]::SetEnvironmentVariable('PATH',$('/opt/homebrew/bin:/opt/homebrew/sbin:'+$ENV:PATH),[System.EnvironmentVariableTarget]::Process)
[System.Environment]::SetEnvironmentVariable('MANPATH',$('/opt/homebrew/share/man'+$(if(${ENV:MANPATH}){':'+${ENV:MANPATH}})+':'),[System.EnvironmentVariableTarget]::Process)
[System.Environment]::SetEnvironmentVariable('INFOPATH',$('/opt/homebrew/share/info'+$(if(${ENV:INFOPATH}){':'+${ENV:INFOPATH}})),[System.EnvironmentVariableTarget]::Process)
$ brew shellenv
set -gx HOMEBREW_PREFIX "/opt/homebrew";
set -gx HOMEBREW_CELLAR "/opt/homebrew/Cellar";
set -gx HOMEBREW_REPOSITORY "/opt/homebrew";
set -q PATH; or set PATH ''; set -gx PATH "/opt/homebrew/bin" "/opt/homebrew/sbin" $PATH;
set -q MANPATH; or set MANPATH ''; set -gx MANPATH "/opt/homebrew/share/man" $MANPATH;
set -q INFOPATH; or set INFOPATH ''; set -gx INFOPATH "/opt/homebrew/share/info" $INFOPATH;
```

The specific case presented in the mentioned discussion could be
mitigated by an additional level of indirection (`{{ output "fish" "-c"
"'brew shellenv'" | trim }}`), that requires that the running system
have the target shells installed, when they are not strictly necessary
with `brew shellenv`.
---
 Library/Homebrew/brew.sh         |  2 +-
 Library/Homebrew/cmd/shellenv.sh | 13 +++++++++++--
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/Library/Homebrew/brew.sh b/Library/Homebrew/brew.sh
index 35a74283fc..37f1112850 100644
--- a/Library/Homebrew/brew.sh
+++ b/Library/Homebrew/brew.sh
@@ -81,7 +81,7 @@ case "$*" in
     ;;
   shellenv)
     source "${HOMEBREW_LIBRARY}/Homebrew/cmd/shellenv.sh"
-    homebrew-shellenv
+    homebrew-shellenv "$1"
     exit 0
     ;;
   formulae)
diff --git a/Library/Homebrew/cmd/shellenv.sh b/Library/Homebrew/cmd/shellenv.sh
index a19a2223d5..2f2af3ff1f 100644
--- a/Library/Homebrew/cmd/shellenv.sh
+++ b/Library/Homebrew/cmd/shellenv.sh
@@ -1,4 +1,4 @@
-#:  * `shellenv`
+#:  * `shellenv [bash|csh|fish|pwsh|sh|tcsh|zsh]`
 #:
 #:  Print export statements. When run in a shell, this installation of Homebrew will be added to your `PATH`, `MANPATH`, and `INFOPATH`.
 #:
@@ -6,6 +6,8 @@
 #:  To help guarantee idempotence, this command produces no output when Homebrew's `bin` and `sbin` directories are first and second
 #:  respectively in your `PATH`. Consider adding evaluation of this command's output to your dotfiles (e.g. `~/.profile`,
 #:  `~/.bash_profile`, or `~/.zprofile`) with: `eval "$(brew shellenv)"`
+#:
+#:  The shell can be specified explicitly with a supported shell name parameter. Unknown shells will output POSIX exports.
 
 # HOMEBREW_CELLAR and HOMEBREW_PREFIX are set by extend/ENV/super.rb
 # HOMEBREW_REPOSITORY is set by bin/brew
@@ -18,7 +20,14 @@ homebrew-shellenv() {
     return
   fi
 
-  case "$(/bin/ps -p "${PPID}" -c -o comm=)" in
+  if [[ -n "$1" ]]
+  then
+    HOMEBREW_SHELL_NAME="$1"
+  else
+    HOMEBREW_SHELL_NAME="$(/bin/ps -p "${PPID}" -c -o comm=)}"
+  fi
+
+  case "${HOMEBREW_SHELL_NAME}" in
     fish | -fish)
       echo "set -gx HOMEBREW_PREFIX \"${HOMEBREW_PREFIX}\";"
       echo "set -gx HOMEBREW_CELLAR \"${HOMEBREW_CELLAR}\";"