Merge pull request #24360 from Homebrew/as-brew-user-relative-brewfile

Preserve working directories when switching users

Library/Homebrew/test/cmd/as-brew-user_spec.rb

@@ -52,7 +52,7 @@ RSpec.describe Homebrew::Cmd::AsBrewUser do
 
   it "runs directly as the prefix owner without sudo" do
     brew_file = test_root/"brew"
-    brew_file.write "#!/bin/bash\nprintf '%s\\n' \"$USER|$HOME|$*|$HOMEBREW_NO_SUDO\"\n"
+    brew_file.write "#!/bin/bash\nprintf '%s\\n' \"$USER|$HOME|$PWD|$*|$HOMEBREW_NO_SUDO\"\n"
     brew_file.chmod(0755)
     stdout, = run_as_brew_user_shell(
       <<~SH,
@@ -69,7 +69,7 @@ RSpec.describe Homebrew::Cmd::AsBrewUser do
                       "HOMEBREW_BREW_FILE" => brew_file.to_s),
     )
 
-    expect(stdout).to eq("brewer|#{test_root}|list|1\n")
+    expect(stdout).to eq("brewer|#{test_root}|#{Dir.pwd}|list|1\n")
   end
 
   it "rejects a root-owned prefix" do
@@ -85,9 +85,9 @@ RSpec.describe Homebrew::Cmd::AsBrewUser do
     expect(stderr).to include("The Homebrew prefix owner must not be root.")
   end
 
-  it "enters the owner's home after switching users" do
+  it "preserves the working directory and relative paths after switching users" do
     brew_file = test_root/"brew"
-    brew_file.write "#!/bin/bash\nprintf '%s\\n' \"$PWD\"\n"
+    brew_file.write "#!/bin/bash\nprintf '%s\\n' \"$PWD\" \"$@\"\n"
     brew_file.chmod(0755)
     stdout, = run_as_brew_user_shell(
       <<~SH,
@@ -97,14 +97,13 @@ RSpec.describe Homebrew::Cmd::AsBrewUser do
           [[ "$1" == -un ]] && { echo operator; return; }
           printf 'brewer:*:503:20::0:0:Brewer:#{test_root}:/bin/zsh\\n'
         }
-        cd() { return 1; }
         sudo() { shift 3; "$@"; }
-        homebrew-as-brew-user list
+        homebrew-as-brew-user bundle --file ./Brewfile
       SH
       macos_env.merge("HOMEBREW_PREFIX" => "/opt/homebrew", "HOMEBREW_BREW_FILE" => brew_file.to_s),
     )
 
-    expect(stdout).to eq("#{test_root}\n")
+    expect(stdout).to eq("#{Dir.pwd}\nbundle\n--file\n./Brewfile\n")
   end
 
   it "selects the prefix owner on Linux" do

Library/Homebrew/test/cmd/as-console-user_spec.rb

@@ -266,7 +266,7 @@ RSpec.describe Homebrew::Cmd::AsConsoleUser do
     expect(stdout).to be_empty
     expect(stderr).to be_empty
     expect(args_file.read).to eq <<~EOS
-      cwd=#{console_home}
+      cwd=#{Dir.pwd}
       -H
       -u
       mike
@@ -275,7 +275,7 @@ RSpec.describe Homebrew::Cmd::AsConsoleUser do
       HOME=#{console_home}
       USER=mike
       LOGNAME=mike
-      PWD=#{console_home}
+      PWD=#{Dir.pwd}
       PATH=/usr/bin:/bin:/usr/sbin:/sbin
       /opt/homebrew/bin/brew
       upgrade

Library/Homebrew/test/cmd/shared_examples/as_user.rb

@@ -74,7 +74,7 @@ RSpec.shared_examples "switching users without sudo" do |command_name = nil|
     stdout, stderr, status = result
 
     expect([stdout.lines(chomp: true), stderr, status.exitstatus]).to eq([
-      ["brewer", test_root.to_s, test_root.to_s, "1", "unset",
+      ["brewer", test_root.to_s, Dir.pwd, "1", "unset",
        "list", "argument with spaces", "", '$(exit 1); * "quotes"'],
       "", 42
     ])

Library/Homebrew/utils/as_user.sh

@@ -78,24 +78,12 @@ homebrew-as-user() {
     fi
   fi
 
-  (
-    if [[ "${command_name}" == as-brew-user ]]
-    then
-      # Expand HOME only after switching to the prefix owner.
-      # shellcheck disable=SC2016
-      set -- /bin/bash -c 'cd -- "$HOME" && exec "$@"' -- "${HOMEBREW_BREW_FILE}" "$@"
-    else
-      cd "${selected_home}" &>/dev/null || odie "Failed to cd to ${selected_home}!"
-      set -- "${HOMEBREW_BREW_FILE}" "$@"
-    fi
-
-    "${user_command[@]}" /usr/bin/env -i \
-      "HOME=${selected_home}" \
-      "USER=${selected_user}" \
-      "LOGNAME=${selected_user}" \
-      "PWD=${selected_home}" \
-      "PATH=/usr/bin:/bin:/usr/sbin:/sbin" \
-      ${HOMEBREW_NO_SUDO:+"HOMEBREW_NO_SUDO=${HOMEBREW_NO_SUDO}"} \
-      "$@"
-  )
+  "${user_command[@]}" /usr/bin/env -i \
+    "HOME=${selected_home}" \
+    "USER=${selected_user}" \
+    "LOGNAME=${selected_user}" \
+    "PWD=${PWD}" \
+    "PATH=/usr/bin:/bin:/usr/sbin:/sbin" \
+    ${HOMEBREW_NO_SUDO:+"HOMEBREW_NO_SUDO=${HOMEBREW_NO_SUDO}"} \
+    "${HOMEBREW_BREW_FILE}" "$@"
 }

docs/Installation.md

@@ -85,6 +85,8 @@ brew as-brew-user install wget
 ```
 
 The command uses the owner's home and a clean environment, switching accounts through sudo when necessary.
+It preserves the caller's working directory, so relative paths resolve as usual.
+The owner must have access to the working directory and any files used by the command.
 When sudo is disabled or unavailable, an already-root process switches through macOS `login` or Linux `runuser` instead.
 These commands use the selected account's primary and supplementary groups.
 Without permission to switch accounts, log in as the owner instead.
@@ -102,6 +104,7 @@ brew as-console-user install wget
 ```
 
 The command uses that user's home and a clean environment.
+Like `as-brew-user`, it preserves the caller's working directory, which the selected user must be able to access.
 An already-root process can switch users even when sudo is disabled or unavailable, using the same fallback as `as-brew-user`.
 Other accounts need sudo access to switch users.
 It fails if no supported console user is logged in.