Don't filter the environment for brew bundle (exec|env|sh)

It's both unexpected and undesirable for `brew bundle (exec|env|sh)` to
filter the environment and makes these tools less useful.

Not filtering the environment, though, causes issues with the
`brew bundle sh` shell. Fix this up and, while we're here, also improve
the formatting for both `zsh` and `bash` (the default) to use nicer and
more consistent prompts and colours.

To simplify this, consolidate some logic in a new
`Utils::Shell.shell_with_prompt` method and add tests for it and a
similar notice for `brew bundle sh`.

Finally, avoid printing out the notice when `HOMEBREW_NO_ENV_HINTS` is
set.

Library/Homebrew/cmd/bundle.rb

@@ -210,18 +210,17 @@ module Homebrew
             _subcommand, *named_args = args.named
             named_args
           when "sh"
-            preferred_shell = Utils::Shell.preferred_path(default: "/bin/bash")
-            subshell = case Utils::Shell.preferred
-            when :zsh
-              "PS1='brew bundle %B%F{green}%~%f%b$ ' #{preferred_shell} -d -f"
-            when :bash
-              "PS1=\"brew bundle \\[\\033[1;32m\\]\\w\\[\\033[0m\\]$ \" #{preferred_shell} --noprofile --norc"
-            else
-              "PS1=\"brew bundle \\[\\033[1;32m\\]\\w\\[\\033[0m\\]$ \" #{preferred_shell}"
+            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
-            $stdout.flush
             ENV["HOMEBREW_FORCE_API_AUTO_UPDATE"] = nil
-            [subshell]
+            [Utils::Shell.shell_with_prompt("brew bundle", preferred_path:, notice:)]
           when "env"
             ["env"]
           end

Library/Homebrew/dev-cmd/sh.rb

@@ -39,32 +39,25 @@ module Homebrew
 
         ENV["VERBOSE"] = "1" if args.verbose?
 
-        preferred_shell = Utils::Shell.preferred_path(default: "/bin/bash")
+        preferred_path = Utils::Shell.preferred_path(default: "/bin/bash")
 
         if args.cmd.present?
-          safe_system(preferred_shell, "-c", args.cmd)
+          safe_system(preferred_path, "-c", args.cmd)
         elsif args.named.present?
-          safe_system(preferred_shell, args.named.first)
+          safe_system(preferred_path, args.named.first)
         else
-          shell_type = Utils::Shell.preferred
-          subshell = case shell_type
-          when :zsh
-            "PS1='brew %B%F{green}%~%f%b$ ' #{preferred_shell} -d -f"
-          when :bash
-            "PS1=\"brew \\[\\033[1;32m\\]\\w\\[\\033[0m\\]$ \" #{preferred_shell} --noprofile --norc"
-          else
-            "PS1=\"brew \\[\\033[1;32m\\]\\w\\[\\033[0m\\]$ \" #{preferred_shell}"
+          notice = unless Homebrew::EnvConfig.no_env_hints?
+            <<~EOS
+              Your shell has been configured to use Homebrew's build environment;
+              this should help you build stuff. Notably though, the system versions of
+              gem and pip will ignore our configuration and insist on using the
+              environment they were built under (mostly). Sadly, scons will also
+              ignore our configuration.
+              Hide these hints with HOMEBREW_NO_ENV_HINTS (see `man brew`).
+              When done, type `exit`.
+            EOS
           end
-          puts <<~EOS
-            Your shell has been configured to use Homebrew's build environment;
-            this should help you build stuff. Notably though, the system versions of
-            gem and pip will ignore our configuration and insist on using the
-            environment they were built under (mostly). Sadly, scons will also
-            ignore our configuration.
-            When done, type `exit`.
-          EOS
-          $stdout.flush
-          safe_system subshell
+          system Utils::Shell.shell_with_prompt("brew", preferred_path:, notice:)
         end
       end
     end

Library/Homebrew/test/utils/shell_spec.rb

@@ -105,4 +105,26 @@ RSpec.describe Utils::Shell do
         .to eq("fish_add_path #{path}")
     end
   end
+
+  describe "::shell_with_prompt" do
+    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}$%f%b ' RPROMPT='[%B%F{red}%~%f%b]' /bin/zsh -f",
+      )
+    end
+
+    it "returns generic shell prompt configuration" do
+      ENV["SHELL"] = "/bin/bash"
+      expect(described_class.shell_with_prompt("test", preferred_path: "/bin/bash", notice: "")).to eq(
+        "PS1=\"\\[\\033[1;32m\\]brew \\[\\033[1;31m\\]\\w \\[\\033[1;34m\\]$\\[\\033[0m\\] \" /bin/bash",
+      )
+    end
+
+    it "outputs notice when provided" do
+      notice = "Test Notice"
+      expect { described_class.shell_with_prompt("test", preferred_path: "/bin/bash", notice: notice) }
+        .to output("#{notice}\n").to_stdout
+    end
+  end
 end

Library/Homebrew/utils/shell.rb

@@ -152,5 +152,21 @@ module Utils
       str.gsub!("\n", "'\n'")
       str
     end
+
+    sig { params(type: String, preferred_path: String, notice: T.nilable(String)).returns(String) }
+    def shell_with_prompt(type, preferred_path:, notice:)
+      preferred = from_path(preferred_path)
+      subshell = case preferred
+      when :zsh
+        "PROMPT='%B%F{green}#{type}%f %F{blue}$%f%b ' RPROMPT='[%B%F{red}%~%f%b]' #{preferred_path} -f"
+      else
+        "PS1=\"\\[\\033[1;32m\\]brew \\[\\033[1;31m\\]\\w \\[\\033[1;34m\\]$\\[\\033[0m\\] \" #{preferred_path}"
+      end
+
+      puts notice if notice.present?
+      $stdout.flush
+
+      subshell
+    end
   end
 end

bin/brew

@@ -265,6 +265,16 @@ then
   export HOMEBREW_GITHUB_HOSTED_RUNNER=1
 fi
 
+# don't filter the environment for `brew bundle (exec|env|sh)`
+if [[ "${1:-}" == "bundle" ]]
+then
+  if [[ "${2:-}" == "exec" || "${2:-}" == "env" || "${2:-}" == "sh" ]]
+  then
+    exec /bin/bash -p "${HOMEBREW_LIBRARY}/Homebrew/brew.sh" "$@"
+    exit $?
+  fi
+fi
+
 # filter the user environment
 PATH="/usr/bin:/bin:/usr/sbin:/sbin"