Audit: make sure service commands exist

Library/Homebrew/formula_cellar_checks.rb

@@ -275,12 +275,22 @@ module FormulaCellarChecks
     "Python formulae that are keg-only should not create `pip3` and `wheel3` symlinks."
   end
 
+  def check_service_command(formula)
+    return unless formula.prefix.directory?
+    return unless formula.service?
+
+    return "Service command blank" if formula.service.command.blank?
+
+    "Service command does not exist" unless File.exist?(formula.service.command.first)
+  end
+
   def audit_installed
     @new_formula ||= false
 
     problem_if_output(check_manpages)
     problem_if_output(check_infopages)
     problem_if_output(check_jars)
+    problem_if_output(check_service_command(formula))
     problem_if_output(check_non_libraries) if @new_formula
     problem_if_output(check_non_executables(formula.bin))
     problem_if_output(check_generic_executables(formula.bin))

Library/Homebrew/service.rb

@@ -118,19 +118,23 @@ module Homebrew
       "#{HOMEBREW_PREFIX}/bin:#{HOMEBREW_PREFIX}/sbin:/usr/bin:/bin:/usr/sbin:/sbin"
     end
 
+    sig { returns(T::Array[String]) }
+    def command
+      instance_eval(&@service_block)
+      @run.select { |i| i.is_a?(Pathname) }
+          .map(&:to_s)
+    end
+
     # Returns a `String` plist.
     # @return [String]
     sig { returns(String) }
     def to_plist
       instance_eval(&@service_block)
 
-      clean_command = @run.select { |i| i.is_a?(Pathname) }
-                          .map(&:to_s)
-
       base = {
         Label:            @formula.plist_name,
         RunAtLoad:        @run_type == RUN_TYPE_IMMEDIATE,
-        ProgramArguments: clean_command,
+        ProgramArguments: command.join,
       }
 
       base[:KeepAlive] = @keep_alive if @keep_alive == true
@@ -148,16 +152,13 @@ module Homebrew
     def to_systemd_unit
       instance_eval(&@service_block)
 
-      clean_command = @run.select { |i| i.is_a?(Pathname) }
-                          .map(&:to_s)
-
       unit = <<~EOS
         [Unit]
         Description=Homebrew generated unit for #{@formula.name}
 
         [Service]
         Type=simple
-        ExecStart=#{clean_command.join}
+        ExecStart=#{command.join}
       EOS
 
       options = []

Library/Homebrew/test/dev-cmd/audit_spec.rb

@@ -488,6 +488,67 @@ module Homebrew
       end
     end
 
+    describe "#check_service_command" do
+      specify "Not installed" do
+        fa = formula_auditor "foo", <<~RUBY
+          class Foo < Formula
+            url "https://brew.sh/foo-1.0.tgz"
+            homepage "https://brew.sh"
+
+            service do
+              run []
+            end
+          end
+        RUBY
+
+        expect(fa.check_service_command(fa.formula)).to match nil
+      end
+
+      specify "No service" do
+        fa = formula_auditor "foo", <<~RUBY
+          class Foo < Formula
+            url "https://brew.sh/foo-1.0.tgz"
+            homepage "https://brew.sh"
+          end
+        RUBY
+
+        mkdir_p fa.formula.prefix
+        expect(fa.check_service_command(fa.formula)).to match nil
+      end
+
+      specify "No command" do
+        fa = formula_auditor "foo", <<~RUBY
+          class Foo < Formula
+            url "https://brew.sh/foo-1.0.tgz"
+            homepage "https://brew.sh"
+
+            service do
+              run []
+            end
+          end
+        RUBY
+
+        mkdir_p fa.formula.prefix
+        expect(fa.check_service_command(fa.formula)).to match "Service command blank"
+      end
+
+      specify "Invalid command" do
+        fa = formula_auditor "foo", <<~RUBY
+          class Foo < Formula
+            url "https://brew.sh/foo-1.0.tgz"
+            homepage "https://brew.sh"
+
+            service do
+              run [HOMEBREW_PREFIX/"bin/something"]
+            end
+          end
+        RUBY
+
+        mkdir_p fa.formula.prefix
+        expect(fa.check_service_command(fa.formula)).to match "Service command does not exist"
+      end
+    end
+
     describe "#audit_github_repository" do
       specify "#audit_github_repository when HOMEBREW_NO_GITHUB_API is set" do
         ENV["HOMEBREW_NO_GITHUB_API"] = "1"

Library/Homebrew/test/service_spec.rb

@@ -123,4 +123,16 @@ describe Homebrew::Service do
       expect(unit).not_to include("Environment=\"PATH=#{std_path}\"")
     end
   end
+
+  describe "#command" do
+    it "returns @run data" do
+      f.class.service do
+        run opt_bin/"beanstalkd"
+        run_type :immediate
+      end
+
+      command = f.service.command
+      expect(command).to eq(["#{HOMEBREW_PREFIX}/opt/#{name}/bin/beanstalkd"])
+    end
+  end
 end