From b4fa65081ff7e60df1e9861669c2a9c213130ce7 Mon Sep 17 00:00:00 2001
From: SimonDarksideJ <darkside@zenithmoon.com>
Date: Mon, 6 May 2024 11:36:13 +0100
Subject: [PATCH] Backporting 2020 fix for recent update

---
 Editor/Utilities/AssemblyDefinitionPostprocessor.cs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Editor/Utilities/AssemblyDefinitionPostprocessor.cs b/Editor/Utilities/AssemblyDefinitionPostprocessor.cs
index 7c3ded8..ce6f15f 100644
--- a/Editor/Utilities/AssemblyDefinitionPostprocessor.cs
+++ b/Editor/Utilities/AssemblyDefinitionPostprocessor.cs
@@ -49,7 +49,11 @@ private void OnPreprocessAsset()
 
                 if (packageVersion.Contains("-pre."))
                 {
+#if UNITY_2021_1_OR_NEWER                    
                     packageVersion = packageVersion[..packageVersion.IndexOf("-", StringComparison.Ordinal)];
+#else
+                    packageVersion = packageVersion.Substring(0, packageVersion.IndexOf("-", StringComparison.Ordinal));
+#endif
                 }
 
                 var newVersion = $"[assembly: AssemblyVersion(\"{packageVersion}\")]";