Merge branch 'throw-error-nda-inputsystem-without-plugin' of https://github.com/Unity-Technologies/InputSystem into throw-error-nda-inputsystem-without-plugin

Author: ritamerkl

Packages/com.unity.inputsystem/InputSystem/Editor/InputSystemPluginControl.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Linq;
 using NUnit.Framework;
 using UnityEditor;
@@ -12,7 +13,7 @@ private static void CheckForExtension()
             ThrowWarningOnMissingPlugin();
         }
 
-        private static readonly BuildTarget[] targetNoPluginNeeded = new BuildTarget[]
+        private static readonly BuildTarget[] TargetNoPluginNeeded =
         {
             BuildTarget.StandaloneOSX,
             BuildTarget.StandaloneWindows,
@@ -35,26 +36,29 @@ private static void CheckForExtension()
         static bool BuildTargetNeedsPlugin()
         {
             BuildTarget target = EditorUserBuildSettings.activeBuildTarget;
-            return !targetNoPluginNeeded.Contains(target);
+            return !TargetNoPluginNeeded.Contains(target);
         }
 
-        private static string plugInName = "com.unity.inputsystem.";
+        private const string PlugInName = "com.unity.inputsystem.";
+
         private static bool IsPluginInstalled()
         {
             var registeredPackages = UnityEditor.PackageManager.PackageInfo.GetAllRegisteredPackages();
             foreach (var package in registeredPackages)
             {
-                if (package.name.StartsWith(plugInName)) //TODO better ??
+                if (package.name.StartsWith(PlugInName)) 
                     return true;
             }
             return false;
+            
+            
         }
 
         private static void ThrowWarningOnMissingPlugin()
         {
-            if (BuildTargetNeedsPlugin() && !IsPluginInstalled())
-                Debug.Log("No plugin installed!");
-            // TODO Assert.
+            if(!BuildTargetNeedsPlugin())
+                return;
+            Debug.Assert(IsPluginInstalled(),"Active Input Handling is set to InputSystem, but no Plugin for "+ EditorUserBuildSettings.activeBuildTarget+" was found. Please install the missing InputSystem package extensions.");
         }
     }
 }