brew (bundle|) sh: use user's configuration but override prompts.

This was more painful that I expected but will allow `brew bundle sh`
and `brew sh` to use the user's configuration but use our custom prompt
for Bash and ZSH.

Library/Homebrew/bundle/commands/exec.rb

@@ -170,6 +170,18 @@ module Homebrew
               end
             end
             return
+          elsif subcommand == "sh"
+            preferred_path = Utils::Shell.preferred_path(default: "/bin/bash")
+            notice = unless Homebrew::EnvConfig.no_env_hints?
+              <<~EOS
+                Your shell has been configured to use a build environment from your `Brewfile`.
+                This should help you build stuff.
+                Hide these hints with HOMEBREW_NO_ENV_HINTS (see `man brew`).
+                When done, type `exit`.
+              EOS
+            end
+            ENV["HOMEBREW_FORCE_API_AUTO_UPDATE"] = nil
+            args = [Utils::Shell.shell_with_prompt("brew bundle", preferred_path:, notice:)]
           end
 
           if services

Library/Homebrew/cmd/bundle.rb

@@ -276,17 +276,7 @@ module Homebrew
             _subcommand, *named_args = args.named
             named_args
           when "sh"
-            preferred_path = Utils::Shell.preferred_path(default: "/bin/bash")
-            notice = unless Homebrew::EnvConfig.no_env_hints?
-              <<~EOS
-                Your shell has been configured to use a build environment from your `Brewfile`.
-                This should help you build stuff.
-                Hide these hints with HOMEBREW_NO_ENV_HINTS (see `man brew`).
-                When done, type `exit`.
-              EOS
-            end
-            ENV["HOMEBREW_FORCE_API_AUTO_UPDATE"] = nil
-            [Utils::Shell.shell_with_prompt("brew bundle", preferred_path:, notice:)]
+            ["sh"]
           when "env"
             ["env"]
           end

Library/Homebrew/test/utils/shell_spec.rb

@@ -107,18 +107,34 @@ RSpec.describe Utils::Shell do
   end
 
   describe "::shell_with_prompt" do
+    let(:home) { HOMEBREW_TEMP }
+    let(:notice) { "" }
+    let(:prompt) { "test" }
+    let(:path) { "/some/path" }
+
     it "returns zsh-specific prompt configuration" do
-      ENV["SHELL"] = "/bin/zsh"
-      expect(described_class.shell_with_prompt("test", preferred_path: "/bin/zsh", notice: "")).to eq(
-        "PROMPT='%B%F{green}test%f %F{blue}$%f%b ' RPROMPT='[%B%F{red}%~%f%b]' /bin/zsh -f",
-      )
+      preferred_path = "/bin/zsh"
+      ENV["SHELL"] = preferred_path
+      ENV["PATH"] = path
+      zdotdir = "#{HOMEBREW_TEMP}/brew-zsh-prompt-#{Process.euid}"
+      expect(described_class.shell_with_prompt(prompt, preferred_path:, notice:, home:)).to eq \
+        "BREW_PROMPT_PATH=\"#{path}\" BREW_PROMPT_TYPE=\"#{prompt}\" ZDOTDIR=\"#{zdotdir}\" #{preferred_path}"
+    end
+
+    it "returns bash-specific prompt configuration" do
+      preferred_path = "/bin/bash"
+      ENV["SHELL"] = "/bin/bash"
+      ENV["PATH"] = path
+      rcfile = "#{HOMEBREW_LIBRARY_PATH}/utils/bash/brew-sh-prompt-bashrc.bash"
+      expect(described_class.shell_with_prompt(prompt, preferred_path:, notice:, home:)).to eq \
+        "BREW_PROMPT_PATH=\"#{path}\" BREW_PROMPT_TYPE=\"#{prompt}\" #{preferred_path} --rcfile \"#{rcfile}\""
     end
 
     it "returns generic shell prompt configuration" do
-      ENV["SHELL"] = "/bin/bash"
-      expect(described_class.shell_with_prompt("test", preferred_path: "/bin/bash", notice: "")).to eq(
-        "PS1=\"\\[\\033[1;32m\\]brew \\[\\033[1;31m\\]\\w \\[\\033[1;34m\\]$\\[\\033[0m\\] \" /bin/bash",
-      )
+      preferred_path = "/bin/dash"
+      ENV["SHELL"] = preferred_path
+      expect(described_class.shell_with_prompt(prompt, preferred_path:, notice:, home:)).to eq \
+        "PS1=\"\\[\\033[1;32m\\]#{prompt} \\[\\033[1;31m\\]\\w \\[\\033[1;34m\\]$\\[\\033[0m\\] \" #{preferred_path}"
     end
 
     it "outputs notice when provided" do

Library/Homebrew/utils/bash/brew-sh-prompt-bashrc.bash

@@ -0,0 +1,12 @@
+# Read the user's ~/.bashrc first
+if [[ -f "${HOME}/.bashrc" ]]
+then
+  source "${HOME}/.bashrc"
+fi
+
+# Override the user's Bash prompt with our custom prompt
+export PS1="\\[\\033[1;32m\\]${BREW_PROMPT_TYPE} \\[\\033[1;31m\\]\\w \\[\\033[1;34m\\]$\\[\\033[0m\\] "
+
+# Add the Homebrew PATH in front of the user's PATH
+export PATH="${BREW_PROMPT_PATH}:${PATH}"
+unset BREW_PROMPT_TYPE BREW_PROMPT_PATH

Library/Homebrew/utils/shell.rb

@@ -153,14 +153,28 @@ module Utils
       str
     end
 
-    sig { params(type: String, preferred_path: String, notice: T.nilable(String)).returns(String) }
-    def shell_with_prompt(type, preferred_path:, notice:)
+    sig { params(type: String, preferred_path: String, notice: T.nilable(String), home: String).returns(String) }
+    def shell_with_prompt(type, preferred_path:, notice:, home: Dir.home)
       preferred = from_path(preferred_path)
+      path = ENV.fetch("PATH")
       subshell = case preferred
       when :zsh
-        "PROMPT='%B%F{green}#{type}%f %F{blue}$%f%b ' RPROMPT='[%B%F{red}%~%f%b]' #{preferred_path} -f"
+        zdotdir = Pathname.new(HOMEBREW_TEMP/"brew-zsh-prompt-#{Process.euid}")
+        zdotdir.mkpath
+        FileUtils.chmod_R(0700, zdotdir)
+        FileUtils.cp(HOMEBREW_LIBRARY_PATH/"utils/zsh/brew-sh-prompt-zshrc.zsh", zdotdir/".zshrc")
+        %w[.zcompdump .zsh_history .zsh_sessions].each do |file|
+          FileUtils.ln_sf("#{home}/#{file}", zdotdir/file)
+        end
+        <<~ZSH.strip
+          BREW_PROMPT_PATH="#{path}" BREW_PROMPT_TYPE="#{type}" ZDOTDIR="#{zdotdir}" #{preferred_path}
+        ZSH
+      when :bash
+        <<~BASH.strip
+          BREW_PROMPT_PATH="#{path}" BREW_PROMPT_TYPE="#{type}" #{preferred_path} --rcfile "#{HOMEBREW_LIBRARY_PATH}/utils/bash/brew-sh-prompt-bashrc.bash"
+        BASH
       else
-        "PS1=\"\\[\\033[1;32m\\]brew \\[\\033[1;31m\\]\\w \\[\\033[1;34m\\]$\\[\\033[0m\\] \" #{preferred_path}"
+        "PS1=\"\\[\\033[1;32m\\]#{type} \\[\\033[1;31m\\]\\w \\[\\033[1;34m\\]$\\[\\033[0m\\] \" #{preferred_path}"
       end
 
       puts notice if notice.present?

Library/Homebrew/utils/zsh/brew-sh-prompt-zshrc.zsh

@@ -0,0 +1,13 @@
+# Read the user's ~/.zshrc first
+if [[ -f "${HOME}/.zshrc" ]]
+then
+  source "${HOME}/.zshrc"
+fi
+
+# Override the user's ZSH prompt with our custom prompt
+export PROMPT="%B%F{green}${BREW_PROMPT_TYPE}%f %F{blue}$%f%b "
+export RPROMPT="[%B%F{red}%~%f%b]"
+
+# Add the Homebrew PATH in front of the user's PATH
+export PATH="${BREW_PROMPT_PATH}:${PATH}"
+unset BREW_PROMPT_TYPE BREW_PROMPT_PATH