Validate platform in canExecute function

Author: Fatme

lib/commands/prepare.ts

@@ -6,9 +6,7 @@ export class PrepareCommand implements ICommand {
 		private $platformCommandParameter: ICommandParameter) { }
 
 	execute(args: string[]): IFuture<void> {
-		return (() => {
-			this.$platformService.preparePlatform(args[0]).wait();
-		}).future<void>()();
+		return this.$platformService.preparePlatform(args[0]);
 	}
 
 	allowedParameters = [this.$platformCommandParameter];

lib/commands/run.ts

@@ -28,7 +28,7 @@ export class RunAndroidCommand extends RunCommandBase implements ICommand {
 		private $platformsData: IPlatformsData) {
 		super($platformService);
 	}
-
+	
 	public allowedParameters: ICommandParameter[] = [];
 
 	public execute(args: string[]): IFuture<void> {

lib/services/platform-service.ts

@@ -146,6 +146,8 @@ export class PlatformService implements IPlatformService {
 
 	public preparePlatform(platform: string): IFuture<void> {
 		return (() => {
+			this.validatePlatform(platform);
+			
 			platform = platform.toLowerCase();
 
 			var platformData = this.$platformsData.getPlatformData(platform);