Don't init ServiceStatus if service is not there (bsc#959730)

src/include/dhcp-server/dialogs.rb

@@ -17,6 +17,7 @@ def initialize_dhcp_server_dialogs(include_target)
 
       Yast.import "Wizard"
       Yast.import "DhcpServer"
+      Yast.import "DhcpServerUI"
       Yast.import "CWM"
 
       Yast.import "Popup"
@@ -46,9 +47,9 @@ def WriteDialog
       Builtins.y2milestone("Running write dialog")
       Wizard.RestoreHelp(Ops.get(@HELPS, "write", ""))
       ret = DhcpServer.Write
-      if ret && restart?
+      if ret && restart_after_writing?
         # Restart only if it's already running
-        @service.try_restart
+        DhcpServerUI.service.try_restart
       end
       # yes-no popup
       if !ret &&
@@ -70,7 +71,7 @@ def SaveAndRestart(event)
       ret = DhcpServer.Write
       if ret
         # Restart only if it's already running
-        @service.try_restart if restart?
+        DhcpServerUI.service.try_restart if restart_after_writing?
       else
         Report.Error(_("Saving the configuration failed"))
       end
@@ -644,14 +645,5 @@ def ConfigTypeSwitch
       return :expert if Mode.config
       DhcpServer.IsConfigurationSimple ? :simple : :expert
     end
-
-  private
-
-    # Checks if the service must be restarted after saving
-    # @return [Boolean]
-    def restart?
-      # If ServiceStatus is used, DhcpServer must be set to write-only
-      DhcpServer.GetWriteOnly() && @status_widget && @status_widget.reload_flag?
-    end
   end
 end

src/include/dhcp-server/widgets.rb

@@ -27,10 +27,22 @@ def initialize_dhcp_server_widgets(include_target)
       Yast.import "TablePopup"
       Yast.import "SuSEFirewall"
       Yast.import "Mode"
+      Yast.import "DhcpServerUI"
+    end
+
+    # Widget to handle the status of the service
+    #
+    # @return [::UI::ServiceStatus] nil if the service is not found (dhcp server
+    #                               not installed)
+    def status_widget
+      return @status_widget unless @status_widget.nil?
 
-      # Init ServiceStatus widget
-      @service = SystemdService.find(DhcpServer.ServiceName())
-      @status_widget = ::UI::ServiceStatus.new(@service, reload_flag_label: :restart)
+      service = DhcpServerUI.service
+      if service
+        @status_widget = ::UI::ServiceStatus.new(service, reload_flag_label: :restart)
+      else
+        nil
+      end
     end
 
     # Function for deleting entry from section
@@ -858,7 +870,7 @@ def init_service_status(_key)
     # Handle function for the ServiceStatus widget
     def handle_service_status(_key, event)
       event_id = event["ID"]
-      if @status_widget.handle_input(event_id) == :enabled_flag
+      if status_widget.handle_input(event_id) == :enabled_flag
         DhcpServer.SetModified
       end
       nil
@@ -868,10 +880,17 @@ def handle_service_status(_key, event)
     # @param [String] id string widget id
     # @param [Hash] event map event that caused storing process
     def store_service_status(_key, _event)
-      DhcpServer.SetStartService(@status_widget.enabled_flag?)
+      DhcpServer.SetStartService(status_widget.enabled_flag?)
       nil
     end
 
+    # Checks if the service must be restarted after saving
+    # @return [Boolean]
+    def restart_after_writing?
+      # If ServiceStatus is used, DhcpServer must be set to write-only
+      DhcpServer.GetWriteOnly() && status_widget && status_widget.reload_flag?
+    end
+
     # Initialize widgets
     # Create description map and copy it into appropriate variable of the
     #  DhcpServer module
@@ -1012,8 +1031,8 @@ def InitWidgets
         },
         "service_status"         => {
           "widget" => :custom,
-          "custom_widget" => @status_widget.widget,
-          "help"   => @status_widget.help,
+          "custom_widget" => status_widget.widget,
+          "help"   => status_widget.help,
           "init"   => fun_ref(method(:init_service_status), "void (string)"),
           "handle" => fun_ref(method(:handle_service_status), "symbol (string, map)"),
           "store"  => fun_ref(method(:store_service_status), "void (string, map)")

src/modules/DhcpServerUI.rb

@@ -24,6 +24,7 @@ def main
       Yast.import "Report"
       Yast.import "Service"
       Yast.import "SuSEFirewall"
+      Yast.import "SystemdService"
 
       @current_entry_type = ""
       @current_entry_id = ""
@@ -81,6 +82,13 @@ def DhcpServerUI
       nil
     end
 
+    # Object representing the DHCP service for its usage in the UI code
+    #
+    # @return [Yast::SystemdServiceClass::Service]
+    def service
+      @service ||= SystemdService.find(DhcpServer.ServiceName())
+    end
+
     publish :variable => :current_entry_type, :type => "string"
     publish :variable => :current_entry_id, :type => "string"
     publish :variable => :current_entry_options, :type => "list <map <string, string>>"