service: add custom service name DSL

The main thing is that this DSL allows us to provide an
interface that can be serialized to the JSON API.

Changes:
- Homebrew::Service
  - Adds `#service_name` and `#plist_name` methods
    - Each is now included in the `#serialize` method as well
  - Eval block on instantiation
    - Before we lazy evaluated this but the cost is not significant
      and it complicated the code a bunch. This only gets called
      during install, when evaluating caveats and in the `brew service`
      command. It skips this evaluation if the service block isn't there.
  - Add `#command?` helper to avoid `#command.blank?` and `#command.present?`
- Formula
  - `#service` now returns a service whenever it's called. This call is
    hidden behind a call to `#service?` most of the time anyway so this
    should be fine.
  - `#plist_name` and `#service_name` now call the methods of the same name
    on the service class. This should have already been in the service object
    to begin with and keeping these methods here helps preserve backwards
    compatibility with people who were overwriting these methods before.
- Caveats
  - Prefer `service#command?`
  - Add helpers for checking on service commands
    - This duplicates some of the work in `brew services`. Maybe we should
      merge that repo in at some point.
  - Check for installed service at `#plist_name` or `#service_name`. I think
    this should be used instead of `Keg#plist_installed?` which checked for any plist file.
    We should think about deprecating `#plist_installed?` in the future.
  - Stop using `ps aux | grep #{formula.plist_name}` to check for service files
    because it was inaccurate (it always returns true on my machine) because the grep
    process is started before the ps process.
  - Note: The behavior is the same as it was before. This means that caveats
    only show up for custom service files on install or if they're already installed.
    Otherwise it won't show up in `brew info`. This is because it has to check
    first if the service file has been installed.
- Utils::Service
  - Add utils for evaluating if a service is installed and running. This duplicates
    some of the work already found in `brew services`. We should seriously consider
    merging `brew services` with the main brew repo in the future since it's already
    tightly coupled to the code in the main repo.
- Formulary.load_formula_from_api
  - Be more explicit about which types can be deserialized into run params since
    it is now possible for run params to be nil.
- Update and add tests

Library/Homebrew/caveats.rb

@@ -2,6 +2,7 @@
 # frozen_string_literal: true
 
 require "language/python"
+require "utils/service"
 
 # A formula's caveats.
 #
@@ -153,33 +154,32 @@ class Caveats
   end
 
   def service_caveats
-    return if !formula.plist && !formula.service? && !keg&.plist_installed?
-    return if formula.service? && formula.service.command.blank?
+    return if !formula.plist && !formula.service? && !Utils::Service.installed?(formula) && !keg&.plist_installed?
+    return if formula.service? && !formula.service.command? && !Utils::Service.installed?(formula)
 
     s = []
 
-    command = if formula.service?
+    command = if formula.service.command?
       formula.service.manual_command
     else
       formula.plist_manual
     end
 
-    return <<~EOS if !which("launchctl") && formula.plist
+    return <<~EOS if !Utils::Service.launchctl? && formula.plist
       #{Formatter.warning("Warning:")} #{formula.name} provides a launchd plist which can only be used on macOS!
       You can manually execute the service instead with:
         #{command}
     EOS
 
     # Brew services only works with these two tools
-    return <<~EOS if !which("systemctl") && !which("launchctl") && formula.service?
+    return <<~EOS if !Utils::Service.systemctl? && !Utils::Service.launchctl? && formula.service.command?
       #{Formatter.warning("Warning:")} #{formula.name} provides a service which can only be used on macOS or systemd!
       You can manually execute the service instead with:
         #{command}
     EOS
 
-    is_running_service = formula.service? && quiet_system("ps aux | grep #{formula.service.command&.first}")
-    startup = formula.service&.requires_root? || formula.plist_startup
-    if is_running_service || (formula.plist && quiet_system("/bin/launchctl list #{formula.plist_name} &>/dev/null"))
+    startup = formula.service.requires_root? || formula.plist_startup
+    if Utils::Service.running?(formula)
       s << "To restart #{formula.full_name} after an upgrade:"
       s << "  #{startup ? "sudo " : ""}brew services restart #{formula.full_name}"
     elsif startup
@@ -190,7 +190,7 @@ class Caveats
       s << "  brew services start #{formula.full_name}"
     end
 
-    if formula.plist_manual || formula.service?
+    if formula.plist_manual || formula.service.command?
       s << "Or, if you don't want/need a background service you can just run:"
       s << "  #{command}"
     end

Library/Homebrew/formula.rb

@@ -1015,13 +1015,13 @@ class Formula
   # The generated launchd {.plist} service name.
   sig { returns(String) }
   def plist_name
-    "homebrew.mxcl.#{name}"
+    service.plist_name
   end
 
   # The generated service name.
   sig { returns(String) }
   def service_name
-    "homebrew.#{name}"
+    service.service_name
   end
 
   # The generated launchd {.plist} file path.
@@ -1051,8 +1051,6 @@ class Formula
 
   # The service specification of the software.
   def service
-    return unless service?
-
     @service ||= Homebrew::Service.new(self, &self.class.service)
   end
 
@@ -2169,7 +2167,7 @@ class Formula
       "disabled"                 => disabled?,
       "disable_date"             => disable_date,
       "disable_reason"           => disable_reason,
-      "service"                  => service&.serialize,
+      "service"                  => (service.serialize if service?),
       "tap_git_head"             => tap_git_head,
       "ruby_source_path"         => ruby_source_path,
       "ruby_source_checksum"     => {},

Library/Homebrew/formula_cellar_checks.rb

@@ -288,7 +288,7 @@ module FormulaCellarChecks
   def check_service_command(formula)
     return unless formula.prefix.directory?
     return unless formula.service?
-    return if formula.service.command.blank?
+    return unless formula.service.command?
 
     "Service command does not exist" unless File.exist?(formula.service.command.first)
   end

Library/Homebrew/formula_installer.rb

@@ -1040,7 +1040,7 @@ on_request: installed_on_request?, options: options)
       return
     end
 
-    if formula.service? && formula.service.command.present?
+    if formula.service? && formula.service.command?
       service_path = formula.systemd_service_path
       service_path.atomic_write(formula.service.to_systemd_unit)
       service_path.chmod 0644
@@ -1052,7 +1052,7 @@ on_request: installed_on_request?, options: options)
       end
     end
 
-    service = if formula.service? && formula.service.command.present?
+    service = if formula.service? && formula.service.command?
       formula.service.to_plist
     elsif formula.plist
       formula.plist

Library/Homebrew/formulary.rb

@@ -261,9 +261,10 @@ module Formulary
         run_params = service_hash.delete(:run)
         service do
           T.bind(self, Homebrew::Service)
-          if run_params.is_a?(Hash)
+          case run_params
+          when Hash
             run(**run_params)
-          else
+          when Array, String
             run run_params
           end
           service_hash.each do |key, arg|

Library/Homebrew/service.rb

@@ -28,7 +28,7 @@ module Homebrew
       @run_type = RUN_TYPE_IMMEDIATE
       @run_at_load = true
       @environment_variables = {}
-      @service_block = block
+      instance_eval(&block) if block
     end
 
     sig { returns(Formula) }
@@ -36,6 +36,40 @@ module Homebrew
       @formula
     end
 
+    sig { returns(String) }
+    def default_plist_name
+      "homebrew.mxcl.#{@formula.name}"
+    end
+
+    sig { params(name: T.nilable(String)).returns(String) }
+    def plist_name(name = nil)
+      case T.unsafe(name)
+      when nil
+        @plist_name ||= default_plist_name
+      when String
+        @plist_name = name
+      else
+        raise TypeError, "Service#plist_name expects a String"
+      end
+    end
+
+    sig { returns(String) }
+    def default_service_name
+      "homebrew.#{@formula.name}"
+    end
+
+    sig { params(name: T.nilable(String)).returns(String) }
+    def service_name(name = nil)
+      case T.unsafe(name)
+      when nil
+        @service_name ||= default_service_name
+      when String
+        @service_name = name
+      else
+        raise TypeError, "Service#service_name expects a String"
+      end
+    end
+
     sig {
       params(
         command: T.nilable(T.any(T::Array[String], String, Pathname)),
@@ -162,7 +196,6 @@ module Homebrew
     # @return [Boolean]
     sig { returns(T::Boolean) }
     def requires_root?
-      eval_service_block
       @require_root.present? && @require_root == true
     end
 
@@ -198,7 +231,6 @@ module Homebrew
     # @return [Boolean]
     sig { returns(T::Boolean) }
     def keep_alive?
-      eval_service_block
       @keep_alive.present? && @keep_alive[:always] != false
     end
 
@@ -357,20 +389,22 @@ module Homebrew
 
     sig { returns(T.nilable(T::Array[String])) }
     def command
-      eval_service_block
       @run&.map(&:to_s)
     end
 
+    sig { returns(T::Boolean) }
+    def command?
+      @run.present?
+    end
+
     # Returns the `String` command to run manually instead of the service.
     # @return [String]
     sig { returns(String) }
     def manual_command
-      eval_service_block
       vars = @environment_variables.except(:PATH)
                                    .map { |k, v| "#{k}=\"#{v}\"" }
 
-      cmd = command
-      out = vars + cmd if cmd.present?
+      out = vars + command if command?
       out.join(" ")
     end
 
@@ -378,7 +412,6 @@ module Homebrew
     # @return [Boolean]
     sig { returns(T::Boolean) }
     def timed?
-      eval_service_block
       @run_type == RUN_TYPE_CRON || @run_type == RUN_TYPE_INTERVAL
     end
 
@@ -388,7 +421,7 @@ module Homebrew
     def to_plist
       # command needs to be first because it initializes all other values
       base = {
-        Label:            @formula.plist_name,
+        Label:            plist_name,
         ProgramArguments: command,
         RunAtLoad:        @run_at_load == true,
       }
@@ -487,10 +520,9 @@ module Homebrew
         WantedBy=timers.target
 
         [Timer]
-        Unit=#{@formula.service_name}
+        Unit=#{service_name}
       EOS
 
-      eval_service_block
       options = []
       options << "Persistent=true" if @run_type == RUN_TYPE_CRON
       options << "OnUnitActiveSec=#{@interval}" if @run_type == RUN_TYPE_INTERVAL
@@ -504,19 +536,18 @@ module Homebrew
       timer + options.join("\n")
     end
 
-    # Only evaluate the service block once.
-    sig { void }
-    def eval_service_block
-      return if @eval_service_block
-
-      instance_eval(&@service_block)
-      @eval_service_block = true
-    end
-
     # Prepare the service hash for inclusion in the formula API JSON.
     sig { returns(Hash) }
     def serialize
-      eval_service_block
+      custom_plist_name = plist_name if plist_name != default_plist_name
+      custom_service_name = service_name if service_name != default_service_name
+
+      unless command?
+        return {
+          plist_name:   custom_plist_name,
+          service_name: custom_service_name,
+        }.compact
+      end
 
       cron_string = if @cron.present?
         [:Minute, :Hour, :Day, :Month, :Weekday]
@@ -527,6 +558,8 @@ module Homebrew
       sockets_string = "#{@sockets[:type]}://#{@sockets[:host]}:#{@sockets[:port]}" if @sockets.present?
 
       {
+        plist_name:            custom_plist_name,
+        service_name:          custom_service_name,
         run:                   @run_params,
         run_type:              @run_type,
         interval:              @interval,
@@ -551,6 +584,17 @@ module Homebrew
     sig { params(api_hash: Hash).returns(Hash) }
     def self.deserialize(api_hash)
       hash = {}
+
+      %w[plist_name service_name].each do |key|
+        next if (value = api_hash[key]).nil?
+
+        hash[key.to_sym] = value
+      end
+
+      # The service hash might not have a "run" command if it only documents
+      # an existing service file with "plist_name" or "service_name".
+      return hash unless api_hash.key?("run")
+
       hash[:run] =
         case api_hash["run"]
         when String

Library/Homebrew/test/caveats_spec.rb

@@ -32,6 +32,10 @@ describe Caveats do
 
   describe "#caveats" do
     context "when f.plist is not nil", :needs_macos do
+      before do
+        allow(Utils::Service).to receive(:launchctl?).and_return(true)
+      end
+
       it "prints error when no launchd is present" do
         f = formula do
           url "foo-1.0"
@@ -39,7 +43,7 @@ describe Caveats do
             "plist_test.plist"
           end
         end
-        allow_any_instance_of(Object).to receive(:which).with("launchctl").and_return(nil)
+        expect(Utils::Service).to receive(:launchctl?).once.and_return(false)
         expect(described_class.new(f).caveats).to include("provides a launchd plist which can only be used on macOS!")
       end
 
@@ -50,7 +54,7 @@ describe Caveats do
             "plist_test.plist"
           end
         end
-        expect(described_class.new(f).caveats).to include("login")
+        expect(described_class.new(f).caveats).to include("restart at login")
       end
 
       it "gives information about service" do
@@ -82,12 +86,25 @@ describe Caveats do
         expect(caveats).to include("WARNING:")
         expect(caveats).to include("tmux")
       end
+
+      # @todo This should get deprecated and the service block `plist_name` method should get used instead.
+      it "prints info when there are custom service files" do
+        f = formula do
+          url "foo-1.0"
+          def plist_name
+            "custom.mxcl.foo"
+          end
+        end
+        expect(Utils::Service).to receive(:installed?).with(f).once.and_return(true)
+        expect(Utils::Service).to receive(:running?).with(f).once.and_return(false)
+        expect(described_class.new(f).caveats).to include("restart at login")
+      end
     end
 
-    context "when f.service is not nil" do
+    context "when service block is defined" do
       before do
-        allow_any_instance_of(Object).to receive(:which).with("launchctl").and_return(true)
-        allow_any_instance_of(Object).to receive(:which).with("systemctl").and_return(true)
+        allow(Utils::Service).to receive(:launchctl?).and_return(true)
+        allow(Utils::Service).to receive(:systemctl?).and_return(true)
       end
 
       it "prints warning when no service deamon is found" do
@@ -97,9 +114,8 @@ describe Caveats do
             run [bin/"cmd"]
           end
         end
-
-        allow_any_instance_of(Object).to receive(:which).with("launchctl").and_return(nil)
-        allow_any_instance_of(Object).to receive(:which).with("systemctl").and_return(nil)
+        expect(Utils::Service).to receive(:launchctl?).twice.and_return(false)
+        expect(Utils::Service).to receive(:systemctl?).once.and_return(false)
         expect(described_class.new(f).caveats).to include("service which can only be used on macOS or systemd!")
       end
 
@@ -111,9 +127,7 @@ describe Caveats do
             require_root true
           end
         end
-        cmd = "#{HOMEBREW_CELLAR}/formula_name/1.0/bin/cmd"
-        allow(Homebrew).to receive(:_system).and_return(true)
-        allow(Homebrew).to receive(:_system).with("ps aux | grep #{cmd}").and_return(false)
+        expect(Utils::Service).to receive(:running?).with(f).once.and_return(false)
         expect(described_class.new(f).caveats).to include("startup")
       end
 
@@ -124,10 +138,8 @@ describe Caveats do
             run [bin/"cmd"]
           end
         end
-        cmd = "#{HOMEBREW_CELLAR}/formula_name/1.0/bin/cmd"
-        allow(Homebrew).to receive(:_system).and_return(true)
-        expect(Homebrew).to receive(:_system).with("ps aux | grep #{cmd}").and_return(false)
-        expect(described_class.new(f).caveats).to include("login")
+        expect(Utils::Service).to receive(:running?).with(f).once.and_return(false)
+        expect(described_class.new(f).caveats).to include("restart at login")
       end
 
       it "gives information about require_root restarting services after upgrade" do
@@ -138,10 +150,8 @@ describe Caveats do
             require_root true
           end
         end
-        cmd = "#{HOMEBREW_CELLAR}/formula_name/1.0/bin/cmd"
         f_obj = described_class.new(f)
-        allow(Homebrew).to receive(:_system).and_return(true)
-        expect(Homebrew).to receive(:_system).with("ps aux | grep #{cmd}").and_return(true)
+        expect(Utils::Service).to receive(:running?).with(f).once.and_return(true)
         expect(f_obj.caveats).to include("  sudo brew services restart #{f.full_name}")
       end
 
@@ -152,10 +162,8 @@ describe Caveats do
             run [bin/"cmd"]
           end
         end
-        cmd = "#{HOMEBREW_CELLAR}/formula_name/1.0/bin/cmd"
         f_obj = described_class.new(f)
-        allow(Homebrew).to receive(:_system).and_return(true)
-        expect(Homebrew).to receive(:_system).with("ps aux | grep #{cmd}").and_return(true)
+        expect(Utils::Service).to receive(:running?).with(f).once.and_return(true)
         expect(f_obj.caveats).to include("  brew services restart #{f.full_name}")
       end
 
@@ -167,10 +175,8 @@ describe Caveats do
             require_root true
           end
         end
-        cmd = "#{HOMEBREW_CELLAR}/formula_name/1.0/bin/cmd"
         f_obj = described_class.new(f)
-        allow(Homebrew).to receive(:_system).and_return(true)
-        allow(Homebrew).to receive(:_system).with("ps aux | grep #{cmd}").and_return(false)
+        expect(Utils::Service).to receive(:running?).with(f).once.and_return(false)
         expect(f_obj.caveats).to include("  sudo brew services start #{f.full_name}")
       end
 
@@ -181,10 +187,8 @@ describe Caveats do
             run [bin/"cmd"]
           end
         end
-        cmd = "#{HOMEBREW_CELLAR}/formula_name/1.0/bin/cmd"
         f_obj = described_class.new(f)
-        allow(Homebrew).to receive(:_system).and_return(true)
-        allow(Homebrew).to receive(:_system).with("ps aux | grep #{cmd}").and_return(false)
+        expect(Utils::Service).to receive(:running?).with(f).once.and_return(false)
         expect(f_obj.caveats).to include("  brew services start #{f.full_name}")
       end
 
@@ -202,6 +206,19 @@ describe Caveats do
         expect(caveats).to include("if you don't want/need a background service")
         expect(caveats).to include("VAR=\"foo\" #{cmd} start")
       end
+
+      it "prints info when there are custom service files" do
+        f = formula do
+          url "foo-1.0"
+          service do
+            plist_name "custom.mxcl.foo"
+            service_name "custom.foo"
+          end
+        end
+        expect(Utils::Service).to receive(:installed?).with(f).once.and_return(true)
+        expect(Utils::Service).to receive(:running?).with(f).once.and_return(false)
+        expect(described_class.new(f).caveats).to include("restart at login")
+      end
     end
 
     context "when f.keg_only is not nil" do

Library/Homebrew/test/formula_installer_spec.rb

@@ -218,21 +218,21 @@ describe FormulaInstaller do
 
     it "works if service is set" do
       formula = Testball.new
+      service = Homebrew::Service.new(formula)
       launchd_service_path = formula.launchd_service_path
       service_path = formula.systemd_service_path
-      service = Homebrew::Service.new(formula)
       formula.opt_prefix.mkpath
 
       expect(formula).to receive(:plist).and_return(nil)
       expect(formula).to receive(:service?).exactly(3).and_return(true)
-      expect(formula).to receive(:service).exactly(5).and_return(service)
+      expect(formula).to receive(:service).exactly(7).and_return(service)
       expect(formula).to receive(:launchd_service_path).and_call_original
       expect(formula).to receive(:systemd_service_path).and_call_original
 
       expect(service).to receive(:timed?).and_return(false)
+      expect(service).to receive(:command?).exactly(2).and_return(true)
       expect(service).to receive(:to_plist).and_return("plist")
       expect(service).to receive(:to_systemd_unit).and_return("unit")
-      expect(service).to receive(:command).exactly(2).and_return("/bin/sh")
 
       installer = described_class.new(formula)
       expect do
@@ -245,24 +245,24 @@ describe FormulaInstaller do
 
     it "works if timed service is set" do
       formula = Testball.new
+      service = Homebrew::Service.new(formula)
       launchd_service_path = formula.launchd_service_path
       service_path = formula.systemd_service_path
       timer_path = formula.systemd_timer_path
-      service = Homebrew::Service.new(formula)
       formula.opt_prefix.mkpath
 
       expect(formula).to receive(:plist).and_return(nil)
       expect(formula).to receive(:service?).exactly(3).and_return(true)
-      expect(formula).to receive(:service).exactly(6).and_return(service)
+      expect(formula).to receive(:service).exactly(9).and_return(service)
       expect(formula).to receive(:launchd_service_path).and_call_original
       expect(formula).to receive(:systemd_service_path).and_call_original
       expect(formula).to receive(:systemd_timer_path).and_call_original
 
-      expect(service).to receive(:to_plist).and_return("plist")
       expect(service).to receive(:timed?).and_return(true)
+      expect(service).to receive(:command?).exactly(2).and_return(true)
+      expect(service).to receive(:to_plist).and_return("plist")
       expect(service).to receive(:to_systemd_unit).and_return("unit")
       expect(service).to receive(:to_systemd_timer).and_return("timer")
-      expect(service).to receive(:command).exactly(2).and_return("/bin/sh")
 
       installer = described_class.new(formula)
       expect do

Library/Homebrew/test/formula_spec.rb

@@ -701,7 +701,7 @@ describe Formula do
         url "https://brew.sh/test-1.0.tbz"
       end
 
-      expect(f.service).to be_nil
+      expect(f.service.serialize).to eq({})
     end
 
     specify "service complicated" do
@@ -717,7 +717,8 @@ describe Formula do
           keep_alive true
         end
       end
-      expect(f.service).not_to be_nil
+      expect(f.service.serialize.keys)
+        .to contain_exactly(:run, :run_type, :error_log_path, :log_path, :working_dir, :keep_alive)
     end
 
     specify "service uses simple run" do
@@ -728,7 +729,21 @@ describe Formula do
         end
       end
 
-      expect(f.service).not_to be_nil
+      expect(f.service.serialize.keys).to contain_exactly(:run, :run_type)
+    end
+
+    specify "service with only custom names" do
+      f = formula do
+        url "https://brew.sh/test-1.0.tbz"
+        service do
+          plist_name "custom.macos.beanstalkd"
+          service_name "custom.linux.beanstalkd"
+        end
+      end
+
+      expect(f.plist_name).to eq("custom.macos.beanstalkd")
+      expect(f.service_name).to eq("custom.linux.beanstalkd")
+      expect(f.service.serialize.keys).to contain_exactly(:plist_name, :service_name)
     end
 
     specify "service helpers return data" do

Library/Homebrew/utils/service.rb

@@ -0,0 +1,50 @@
+# typed: true
+# frozen_string_literal: true
+
+module Utils
+  # Helpers for `brew services` related code.
+  module Service
+    # Check if a service is running for a specified formula.
+    sig { params(formula: Formula).returns(T::Boolean) }
+    def self.running?(formula)
+      if launchctl?
+        quiet_system(launchctl, "list", formula.plist_name)
+      elsif systemctl?
+        quiet_system(systemctl, "is-active", "--quiet", formula.service_name)
+      end
+    end
+
+    # Check if a service file is installed in the expected location.
+    sig { params(formula: Formula).returns(T::Boolean) }
+    def self.installed?(formula)
+      (launchctl? && formula.launchd_service_path.exist?) ||
+        (systemctl? && formula.systemd_service_path.exist?)
+    end
+
+    # Path to launchctl binary.
+    sig { returns(T.nilable(Pathname)) }
+    def self.launchctl
+      return @launchctl if defined? @launchctl
+
+      @launchctl = which("launchctl")
+    end
+
+    # Path to systemctl binary.
+    sig { returns(T.nilable(Pathname)) }
+    def self.systemctl
+      return @systemctl if defined? @systemctl
+
+      @systemctl = which("systemctl")
+    end
+
+    sig { returns(T::Boolean) }
+    def self.launchctl?
+      !launchctl.nil?
+    end
+
+    sig { returns(T::Boolean) }
+    def self.systemctl?
+      !systemctl.nil?
+    end
+  end
+end

Library/Homebrew/utils/service.rbi

@@ -0,0 +1,7 @@
+# typed: strict
+
+module Utils
+  module Service
+    include Kernel
+  end
+end