debug: support debugServer per configuration

fixes #13783

src/vs/workbench/parts/debug/node/debugAdapter.ts

@@ -142,6 +142,10 @@ export class Adapter {
 					enum: [request],
 					description: nls.localize('debugRequest', "Request type of configuration. Can be \"launch\" or \"attach\"."),
 				};
+				properties.debugServer = {
+					type: 'number',
+					description: nls.localize('debugServer', "For debug extension development only: if a port is specified VS Code tries to connect to a debug adapter running in server mode")
+				};
 				properties.configurationNames = {
 					type: 'array',
 					default: [],

src/vs/workbench/parts/debug/node/debugConfigurationManager.ts

@@ -158,7 +158,12 @@ const schema: IJSONSchema = {
 				'type': 'object',
 				oneOf: []
 			}
-		}
+		},
+		// TODO@Isidor remove support for this in December
+		debugServer: {
+			type: 'number',
+			description: nls.localize('app.launch.json.debugServer', "DEPRECATED: please move debugServer inside a configuration.")
+		},
 	}
 };
 
@@ -259,7 +264,7 @@ export class ConfigurationManager implements debug.IConfigurationManager {
 
 			result = filtered.length === 1 ? filtered[0] : config.configurations[0];
 			result = objects.deepClone(result);
-			if (config && result) {
+			if (config && result && config.debugServer) {
 				result.debugServer = config.debugServer;
 			}
 		}