don't overwrite user files that happened to be called the same as the input actions target

Author: K-Tone

Packages/com.unity.inputsystem/InputSystem/Editor/AssetImporter/InputActionImporter.cs

@@ -247,6 +247,18 @@ private static void GenerateWrapperCode(AssetImportContext ctx, InputActionAsset
             if (!Directory.Exists(dir))
                 Directory.CreateDirectory(dir);
 
+            // Check for the case where the target file already exists.
+            // If it does, we don't want to overwrite it unless it's been generated by us before.
+            if (File.Exists(wrapperFilePath))
+            {
+                var text = File.ReadAllText(wrapperFilePath);
+                var autoGeneratedMarker = "This code was auto-generated by com.unity.inputsystem";
+                if (!text.Contains(autoGeneratedMarker))
+                {
+                    throw new Exception($"The target file for Input Actions code generation already exists: {wrapperFilePath}. Since it doesn't look to contain Input generated code that we can safely overwrite, we stopped to prevent any data loss. Consider renaming. ");
+                }
+            }
+
             var options = new InputActionCodeGenerator.Options
             {
                 sourceAssetPath = ctx.assetPath,