Support for nuget package with multiple Roslyn version analyzers

src/NuGetForUnity/Editor/NugetAssetPostprocessor.cs

@@ -31,11 +31,32 @@ namespace NugetForUnity
     /// </summary>
     public class NugetAssetPostprocessor : AssetPostprocessor
     {
+        private const string MaxSupportedRoslynVersion =
+#if UNITY_2022_3_OR_NEWER && !UNITY_2022_3_1 && !UNITY_2022_3_2 && !UNITY_2022_3_3 && !UNITY_2022_3_3 && !UNITY_2022_3_4 && !UNITY_2022_3_5 && !UNITY_2022_3_6 && !UNITY_2022_3_7 && !UNITY_2022_3_8 && !UNITY_2022_3_9 && !UNITY_2022_3_10 && !UNITY_2022_3_11
+            "4.3.0";
+#elif UNITY_2022_2_OR_NEWER
+            "4.1.0";
+#elif UNITY_2021_2_OR_NEWER
+            "3.8.0";
+#else
+            "";
+#endif
+
         /// <summary>
         ///     Folder used to store Roslyn-Analyzers inside NuGet packages.
         /// </summary>
         private const string AnalyzersFolderName = "analyzers";
 
+        /// <summary>
+        ///     Folder of root before the version of analyzers was split.
+        /// </summary>
+        private static readonly string AnalyzersRoslynVersionsFolderName = Path.Combine(AnalyzersFolderName, "dotnet");
+
+        /// <summary>
+        ///     Prefix for roslyn versioning of dll asset path.
+        /// </summary>
+        private static readonly string AnalyzersRoslynVersionSubFolderPrefix = Path.Combine(AnalyzersRoslynVersionsFolderName, "roslyn");
+
         /// <summary>
         ///     Used to mark an asset as already processed by this class.
         /// </summary>
@@ -180,6 +201,21 @@ private static string GetNuGetRepositoryPath()
             return ConfigurationManager.NugetConfigFile.RepositoryPath + Path.DirectorySeparatorChar;
         }
 
+        [CanBeNull]
+        private static string GetRoslynVersionNumberFromAnalyzerPath(string analyzerAssetPath)
+        {
+            var versionPrefixIndex = analyzerAssetPath.IndexOf(AnalyzersRoslynVersionSubFolderPrefix, StringComparison.Ordinal);
+            if (versionPrefixIndex < 0)
+            {
+                return null;
+            }
+
+            var startIndex = versionPrefixIndex + AnalyzersRoslynVersionSubFolderPrefix.Length;
+            var separatorIndex = analyzerAssetPath.IndexOf(Path.DirectorySeparatorChar, startIndex);
+            var length = separatorIndex >= 0 ? separatorIndex - startIndex : analyzerAssetPath.Length - startIndex;
+            return analyzerAssetPath.Substring(startIndex, length);
+        }
+
         private static void ModifyImportSettingsOfRoslynAnalyzer([NotNull] PluginImporter plugin, bool reimport)
         {
             plugin.SetCompatibleWithAnyPlatform(false);
@@ -189,7 +225,29 @@ private static void ModifyImportSettingsOfRoslynAnalyzer([NotNull] PluginImporte
                 plugin.SetExcludeFromAnyPlatform(platform, false);
             }
 
-            AssetDatabase.SetLabels(plugin, new[] { RoslynAnalyzerLabel, ProcessedLabel });
+            var enableRoslynAnalyzer = true;
+
+            // The nuget package can contain analyzers for multiple Roslyn versions.
+            // In that case, for the same package, the most recent version must be chosen out of those available for the current Unity version.
+            var assetPath = Path.GetFullPath(plugin.assetPath);
+            var assetRoslynVersion = GetRoslynVersionNumberFromAnalyzerPath(assetPath);
+            if (assetRoslynVersion != null)
+            {
+                var versionPrefixIndex = assetPath.IndexOf(AnalyzersRoslynVersionsFolderName, StringComparison.Ordinal);
+                var analyzersVersionsRoot = Path.Combine(assetPath.Substring(0, versionPrefixIndex), AnalyzersRoslynVersionsFolderName);
+                var analyzersFolders = Directory.GetDirectories(analyzersVersionsRoot);
+                var enabledRoslynVersions = analyzersFolders.Select(GetRoslynVersionNumberFromAnalyzerPath)
+                    .Where(version => version != null && string.CompareOrdinal(version, MaxSupportedRoslynVersion) <= 0)
+                    .ToArray();
+
+                // If most recent valid analyzers exist elsewhere, remove label `RoslynAnalyzer`
+                if (!enabledRoslynVersions.Contains(assetRoslynVersion) || string.CompareOrdinal(assetRoslynVersion, enabledRoslynVersions.Max()) < 0)
+                {
+                    enableRoslynAnalyzer = false;
+                }
+            }
+
+            AssetDatabase.SetLabels(plugin, enableRoslynAnalyzer ? new[] { RoslynAnalyzerLabel, ProcessedLabel } : new[] { ProcessedLabel });
 
             if (reimport)
             {