cmd/shellenv.sh: make brew shellenv idempotent

Library/Homebrew/cmd/shellenv.sh

@@ -3,6 +3,7 @@
 #:  Print export statements. When run in a shell, this installation of Homebrew will be added to your `PATH`, `MANPATH`, and `INFOPATH`.
 #:
 #:  The variables `HOMEBREW_PREFIX`, `HOMEBREW_CELLAR` and `HOMEBREW_REPOSITORY` are also exported to avoid querying them multiple times.
+#:  The variable `HOMEBREW_SHELLENV_SET` will be exported to avoid adding duplicate entries to the environment variables.
 #:  Consider adding evaluation of this command's output to your dotfiles (e.g. `~/.profile`, `~/.bash_profile`, or `~/.zprofile`) with: `eval $(brew shellenv)`
 
 # HOMEBREW_CELLAR and HOMEBREW_PREFIX are set by extend/ENV/super.rb
@@ -10,29 +11,35 @@
 # shellcheck disable=SC2154
 homebrew-shellenv() {
   case "$(/bin/ps -p "${PPID}" -c -o comm=)" in
-    fish|-fish)
+    fish | -fish)
       echo "set -gx HOMEBREW_PREFIX \"${HOMEBREW_PREFIX}\";"
       echo "set -gx HOMEBREW_CELLAR \"${HOMEBREW_CELLAR}\";"
       echo "set -gx HOMEBREW_REPOSITORY \"${HOMEBREW_REPOSITORY}\";"
+      [[ -n "${HOMEBREW_SHELLENV_SET}" ]] && return
       echo "set -q PATH; or set PATH ''; set -gx PATH \"${HOMEBREW_PREFIX}/bin\" \"${HOMEBREW_PREFIX}/sbin\" \$PATH;"
       echo "set -q MANPATH; or set MANPATH ''; set -gx MANPATH \"${HOMEBREW_PREFIX}/share/man\" \$MANPATH;"
       echo "set -q INFOPATH; or set INFOPATH ''; set -gx INFOPATH \"${HOMEBREW_PREFIX}/share/info\" \$INFOPATH;"
+      echo "set -gx HOMEBREW_SHELLENV_SET 1;"
       ;;
-    csh|-csh|tcsh|-tcsh)
+    csh | -csh | tcsh | -tcsh)
       echo "setenv HOMEBREW_PREFIX ${HOMEBREW_PREFIX};"
       echo "setenv HOMEBREW_CELLAR ${HOMEBREW_CELLAR};"
       echo "setenv HOMEBREW_REPOSITORY ${HOMEBREW_REPOSITORY};"
+      [[ -n "${HOMEBREW_SHELLENV_SET}" ]] && return
       echo "setenv PATH ${HOMEBREW_PREFIX}/bin:${HOMEBREW_PREFIX}/sbin:\$PATH;"
       echo "setenv MANPATH ${HOMEBREW_PREFIX}/share/man\`[ \${?MANPATH} == 1 ] && echo \":\${MANPATH}\"\`:;"
       echo "setenv INFOPATH ${HOMEBREW_PREFIX}/share/info\`[ \${?INFOPATH} == 1 ] && echo \":\${INFOPATH}\"\`;"
+      echo "setenv HOMEBREW_SHELLENV_SET 1;"
       ;;
     *)
       echo "export HOMEBREW_PREFIX=\"${HOMEBREW_PREFIX}\";"
       echo "export HOMEBREW_CELLAR=\"${HOMEBREW_CELLAR}\";"
       echo "export HOMEBREW_REPOSITORY=\"${HOMEBREW_REPOSITORY}\";"
+      [[ -n "${HOMEBREW_SHELLENV_SET}" ]] && return
       echo "export PATH=\"${HOMEBREW_PREFIX}/bin:${HOMEBREW_PREFIX}/sbin\${PATH+:\$PATH}\";"
       echo "export MANPATH=\"${HOMEBREW_PREFIX}/share/man\${MANPATH+:\$MANPATH}:\";"
       echo "export INFOPATH=\"${HOMEBREW_PREFIX}/share/info:\${INFOPATH:-}\";"
+      echo "export HOMEBREW_SHELLENV_SET=1;"
       ;;
   esac
 }

Library/Homebrew/env_config.rb

@@ -305,6 +305,10 @@ module Homebrew
                      "useful to avoid long-running Homebrew commands being killed due to no output.",
         boolean:     true,
       },
+      HOMEBREW_SHELLENV_SET:                  {
+        description: "If set, `brew shellenv` skips export statements for paths.",
+        boolean:     true,
+      },
       all_proxy:                              {
         description: "Use this SOCKS5 proxy for `curl`(1), `git`(1) and `svn`(1) when downloading through Homebrew.",
       },

docs/Manpage.md

@@ -565,6 +565,7 @@ The search for *`text`* is extended online to `homebrew/core` and `homebrew/cask
 Print export statements. When run in a shell, this installation of Homebrew will be added to your `PATH`, `MANPATH`, and `INFOPATH`.
 
 The variables `HOMEBREW_PREFIX`, `HOMEBREW_CELLAR` and `HOMEBREW_REPOSITORY` are also exported to avoid querying them multiple times.
+The variable `HOMEBREW_SHELLENV_SET` will be exported to avoid adding duplicate entries to the environment variables.
 Consider adding evaluation of this command's output to your dotfiles (e.g. `~/.profile`, `~/.bash_profile`, or `~/.zprofile`) with: `eval $(brew shellenv)`
 
 ### `tap` [*`options`*] [*`user`*`/`*`repo`*] [*`URL`*]
@@ -2087,6 +2088,9 @@ example, run `export HOMEBREW_NO_INSECURE_REDIRECT=1` rather than just
 - `HOMEBREW_VERBOSE_USING_DOTS`
   <br>If set, verbose output will print a `.` no more than once a minute. This can be useful to avoid long-running Homebrew commands being killed due to no output.
 
+- `HOMEBREW_SHELLENV_SET`
+  <br>If set, `brew shellenv` skips export statements for paths.
+
 - `all_proxy`
   <br>Use this SOCKS5 proxy for `curl`(1), `git`(1) and `svn`(1) when downloading through Homebrew.
 

manpages/brew.1

@@ -784,7 +784,7 @@ Search for \fItext\fR in the given database\.
 Print export statements\. When run in a shell, this installation of Homebrew will be added to your \fBPATH\fR, \fBMANPATH\fR, and \fBINFOPATH\fR\.
 .
 .P
-The variables \fBHOMEBREW_PREFIX\fR, \fBHOMEBREW_CELLAR\fR and \fBHOMEBREW_REPOSITORY\fR are also exported to avoid querying them multiple times\. Consider adding evaluation of this command\'s output to your dotfiles (e\.g\. \fB~/\.profile\fR, \fB~/\.bash_profile\fR, or \fB~/\.zprofile\fR) with: \fBeval $(brew shellenv)\fR
+The variables \fBHOMEBREW_PREFIX\fR, \fBHOMEBREW_CELLAR\fR and \fBHOMEBREW_REPOSITORY\fR are also exported to avoid querying them multiple times\. The variable \fBHOMEBREW_SHELLENV_SET\fR will be exported to avoid adding duplicate entries to the environment variables\. Consider adding evaluation of this command\'s output to your dotfiles (e\.g\. \fB~/\.profile\fR, \fB~/\.bash_profile\fR, or \fB~/\.zprofile\fR) with: \fBeval $(brew shellenv)\fR
 .
 .SS "\fBtap\fR [\fIoptions\fR] [\fIuser\fR\fB/\fR\fIrepo\fR] [\fIURL\fR]"
 Tap a formula repository\.
@@ -3040,6 +3040,12 @@ If set, always assume \fB\-\-debug\fR when running commands\.
 If set, verbose output will print a \fB\.\fR no more than once a minute\. This can be useful to avoid long\-running Homebrew commands being killed due to no output\.
 .
 .TP
+\fBHOMEBREW_SHELLENV_SET\fR
+.
+.br
+If set, \fBbrew shellenv\fR skips export statements for paths\.
+.
+.TP
 \fBall_proxy\fR
 .
 .br