use default config file if no config was specified and default config file exists

src/main/kotlin/org/domaindrivenarchitecture/provs/desktop/application/Application.kt

@@ -8,6 +8,8 @@ import org.domaindrivenarchitecture.provs.desktop.infrastructure.getConfig
 import org.domaindrivenarchitecture.provs.framework.core.cli.createProvInstance
 import org.domaindrivenarchitecture.provs.framework.core.cli.quit
 import java.io.FileNotFoundException
+import java.nio.file.Files
+import kotlin.io.path.Path
 import kotlin.system.exitProcess
 
 /**
@@ -21,22 +23,28 @@ fun main(args: Array<String>) {
         exitProcess(1)
     }
 
-    val config = if (cmd.configFile == null) DesktopConfig() else
+    val defaultConfigFileName = "desktop-config.yaml"
+    val config = if ((cmd.configFile == null) && !Files.isRegularFile(Path(defaultConfigFileName))) {
+        println("ATTENTION: No config provided => using an empty config.")
+        DesktopConfig()
+    } else {
+        val configFileName = cmd.configFile?.fileName ?: defaultConfigFileName
         try {
-            getConfig(cmd.configFile.fileName)
+            getConfig(configFileName)
         } catch (e: SerializationException) {
             println(
-                "Error: File \"${cmd.configFile.fileName}\" has an invalid format and or invalid data."
+                "Error: File \"${configFileName}\" has an invalid format and or invalid data."
             )
             null
         } catch (e: FileNotFoundException) {
             println(
-                "Error: File\u001b[31m ${cmd.configFile.fileName} \u001b[0m was not found.\n" +
-                        "Pls copy file \u001B[31m desktop-config-example.yaml \u001B[0m to file \u001B[31m ${cmd.configFile.fileName} \u001B[0m " +
+                "Error: File\u001b[31m ${configFileName} \u001b[0m was not found.\n" +
+                        "Pls copy file \u001B[31m desktop-config-example.yaml \u001B[0m to file \u001B[31m ${configFileName} \u001B[0m " +
                         "and change the content according to your needs."
             )
             null
         }
+    }
 
     if (config == null) {
         println("No suitable config found.")

src/main/kotlin/org/domaindrivenarchitecture/provs/desktop/infrastructure/DesktopConfigRepository.kt

@@ -11,7 +11,7 @@ import java.io.FileWriter
  * Returns DesktopConfig; data for config is read from specified file.
  * Throws exceptions FileNotFoundException, SerializationException if file is not found resp. cannot be parsed.
  */
-fun getConfig(filename: String = "desktop-config.yaml"): DesktopConfig = readFromFile(filename).yamlToType()
+fun getConfig(filename: String): DesktopConfig = readFromFile(filename).yamlToType()
 
 
 @Suppress("unused")