added hotreload

Packages/com.singularitygroup.hotreload/Editor/CompileChecker/LegacyCompileChecker.cs

@@ -0,0 +1,55 @@
+#if !UNITY_2019_1_OR_NEWER
+using System;
+using System.Globalization;
+using System.IO;
+using System.Threading.Tasks;
+
+namespace SingularityGroup.HotReload.Editor {
+    class LegacyCompileChecker : ICompileChecker {
+        const string timestampFilePath = PackageConst.LibraryCachePath + "/lastCompileTimestamp.txt";
+        public bool hasCompileErrors { get; }
+        const string assemblyPath = "Library/ScriptAssemblies";
+        bool recompile;
+        public LegacyCompileChecker() {
+            Task.Run(() => {
+                var info = new DirectoryInfo(assemblyPath);
+                if(!info.Exists) {
+                    return;
+                }
+                var currentCompileTimestamp = default(DateTime);
+                foreach (var file in info.GetFiles("*.dll")) {
+                    var fileWriteDate = file.LastWriteTimeUtc;
+                    if(fileWriteDate > currentCompileTimestamp) {
+                        currentCompileTimestamp = fileWriteDate;
+                    }
+                }
+                if(File.Exists(timestampFilePath)) {
+                    var lastTimestampStr = File.ReadAllText(timestampFilePath);
+                    var lastTimestamp = DateTime.ParseExact(lastTimestampStr, "o", CultureInfo.CurrentCulture).ToUniversalTime();
+                    if(currentCompileTimestamp > lastTimestamp) {
+                        ThreadUtility.RunOnMainThread(() => {
+                            recompile = true;
+                            _onCompilationFinished?.Invoke();
+                        });
+                    }
+                }
+                Directory.CreateDirectory(Path.GetDirectoryName(timestampFilePath));
+                File.WriteAllText(timestampFilePath, currentCompileTimestamp.ToString("o"));
+            });
+        }
+
+        Action _onCompilationFinished;
+        public event Action onCompilationFinished {
+            add {
+                if(recompile && value != null) {
+                    value();
+                }
+                _onCompilationFinished += value;
+            }
+            remove {
+                _onCompilationFinished -= value;
+            }
+        }
+    }
+}
+#endif