Validate project location on Unity export.

Author: timbotimbo

example/unity/DemoApp/Assets/FlutterUnityIntegration/Editor/Build.cs

@@ -145,6 +145,11 @@ private static void BuildWindowsOS(String path)
 
         private static void BuildWebGL(String path)
         {
+            // Check if the Unity project is in the expected location
+            if (!IsProjectLocationValid(path, "web")) {
+                return;
+            }
+
             // Switch to Android standalone build.
             EditorUserBuildSettings.SwitchActiveBuildTarget(BuildTargetGroup.Android, BuildTarget.Android);
 
@@ -178,6 +183,11 @@ private static void BuildWebGL(String path)
 
         private static void DoBuildAndroid(String buildPath, bool isPlugin, bool isReleaseBuild)
         {
+            // Check if the Unity project is in the expected location
+            if (!IsProjectLocationValid(AndroidExportPath, "android")) {
+                return;
+            }
+
             // Switch to Android standalone build.
             EditorUserBuildSettings.SwitchActiveBuildTarget(BuildTargetGroup.Android, BuildTarget.Android);
 
@@ -359,6 +369,11 @@ private static void ModifyAndroidGradle(bool isPlugin)
 
         private static void BuildIOS(String path, bool isReleaseBuild)
         {
+            // Check if the Unity project is in the expected location
+            if (!IsProjectLocationValid(path, "ios")) {
+                return;
+            }
+
             bool abortBuild = false;
 
             // abort iOS export if #UNITY_IOS is false.
@@ -773,6 +788,21 @@ private static async void BuildUnityFrameworkArchive()
 
         }
 
+
+        // check if the Unity project is in the expected location
+        private static bool IsProjectLocationValid(string unityLibraryPath, string platform)
+        { 
+            // android, ios and web use platform/unityLibrary, move up one step.
+            string platformPath = Path.Combine(unityLibraryPath, "../");
+            if (!Directory.Exists(platformPath))
+            {
+                Debug.LogError($"Could not find the Flutter project {platform} folder. Make sure the Unity project folder is located in '<flutter-project>/unity/<unity-project-folder>' .");
+                Debug.Log($"-- Build: Failed --");
+                return false;
+            }
+            return true;
+        }
+
         //#endregion
     }
 }