Add postinstall support for brew and cask

This allows `postinstall` to be used to run a command after a formula
or cask is installed.

While we're here, also adjust the `restart_service` behaviour to
correctly match the comment i.e. require `always` to restart every
time and otherwise just restart on an install or upgrade of a formula.

README.md

@@ -37,10 +37,12 @@ cask_args appdir: "~/Applications", require_sha: true
 
 # 'brew install'
 brew "imagemagick"
-# 'brew install --with-rmtp', 'brew link --overwrite', 'brew services restart' on version changes
-brew "denji/nginx/nginx-full", link: :overwrite, args: ["with-rmtp"], restart_service: :changed
+# 'brew install --with-rmtp', 'brew link --overwrite', 'brew services restart' even if no install/upgrade
+brew "denji/nginx/nginx-full", link: :overwrite, args: ["with-rmtp"], restart_service: :always
 # 'brew install', always 'brew services restart', 'brew link', 'brew unlink mysql' (if it is installed)
 brew "[email protected]", restart_service: true, link: true, conflicts_with: ["mysql"]
+# 'brew install' and run a command if installer or upgraded.
+brew "postgresql@16", postinstall: "${HOMEBREW_PREFIX}/opt/postgresql@16/bin/postgres -D ${HOMEBREW_PREFIX}/var/postgresql@16"
 # install only on specified OS
 brew "gnupg" if OS.mac?
 brew "glibc" if OS.linux?
@@ -55,6 +57,8 @@ cask "firefox", args: { no_quarantine: true }
 cask "opera", greedy: true
 # 'brew install --cask' only if '/usr/libexec/java_home --failfast' fails
 cask "java" unless system "/usr/libexec/java_home", "--failfast"
+# 'brew install --cask' and run a command if installer or upgraded.
+cask "google-cloud-sdk", postinstall: "${HOMEBREW_PREFIX}/bin/gcloud components update"
 
 # 'mas install'
 mas "1Password", id: 443_987_910

lib/bundle/brew_installer.rb

@@ -24,6 +24,7 @@ def initialize(name, options = {})
       @restart_service = options[:restart_service]
       @start_service = options.fetch(:start_service, @restart_service)
       @link = options.fetch(:link, nil)
+      @postinstall = options.fetch(:postinstall, nil)
       @changed = nil
     end
 
@@ -50,8 +51,12 @@ def install(preinstall: true, no_upgrade: false, verbose: false, force: false)
           service_result = service_change_state!(verbose:)
           result &&= service_result
         end
+
         link_result = link_change_state!(verbose:)
         result &&= link_result
+
+        postinstall_result = postinstall_change_state!(verbose:)
+        result &&= postinstall_result
       end
 
       result
@@ -83,7 +88,7 @@ def restart_service_needed?
       return false unless restart_service?
 
       # Restart if `restart_service: :always`, or if the formula was installed or upgraded
-      @restart_service.to_s != "changed" || changed?
+      @restart_service.to_s == "always" || changed?
     end
 
     def changed?
@@ -132,6 +137,14 @@ def link_change_state!(verbose: false)
       true
     end
 
+    def postinstall_change_state!(verbose:)
+      return true unless @postinstall.present?
+      return true unless changed?
+
+      puts "Running postinstall for #{@name}." if verbose
+      Bundle.system(@postinstall, verbose:)
+    end
+
     def self.formula_installed_and_up_to_date?(formula, no_upgrade: false)
       return false unless formula_installed?(formula)
       return true if no_upgrade

lib/bundle/cask_installer.rb

@@ -56,6 +56,8 @@ def install(name, preinstall: true, no_upgrade: false, verbose: false, force: fa
 
       return false unless Bundle.brew("install", "--cask", full_name, *args, verbose:)
 
+      # TODO: run postinstall if installed or upgraded
+
       installed_casks << name
       true
     end