Workaroud when AssetDatabase.CreateFolder failed

source/VersionHandlerImpl/src/FileUtils.cs

@@ -618,6 +618,22 @@ public static RemoveAssetsResult RemoveAssets(IEnumerable<string> filenames,
             return result;
         }
 
+        /// <summary>
+        /// Check if a guid returned from Unity API is valid.
+        /// </summary>
+        /// <param name="guid">GUID returned from Unity API.</param>
+        /// <returns>True if the guid is valid.</returns>
+        internal static bool IsValidGuid(string guidStr) {
+            if(String.IsNullOrEmpty(guidStr)) return false;
+            try {
+                var guid = new Guid(guidStr);
+                if (guid == Guid.Empty) return false;
+            } catch (FormatException e) {
+                return false;
+            }
+            return true;
+        }
+
         /// <summary>
         /// Recursively create all parent folders given a path.
         /// </summary>
@@ -632,7 +648,15 @@ public static bool CreateFolder(string path) {
             if (!CreateFolder(parentFolder)) {
                 return false;
             }
-            return !String.IsNullOrEmpty(AssetDatabase.CreateFolder(parentFolder, di.Name));
+
+            // Try to use Unity API to create folder. However, some versions of Unity has issue to
+            // create folders with version number in it like '9.0.0'. In this case, instead of
+            // returnig empty guid, it can return guids with all zeroes.
+            if (IsValidGuid(AssetDatabase.CreateFolder(parentFolder, di.Name))) {
+                return true;
+            }
+
+            return Directory.CreateDirectory(path) != null;
         }
 
         /// <summary>

source/VersionHandlerImpl/unit_tests/src/FileUtilsTest.cs

@@ -391,5 +391,50 @@ public void ReplaceBaseAssetsOrPackagesFolder() {
                     "Foo/Bar", "Assets"),
                 Is.EqualTo("Foo/Bar"));
         }
+
+        /// <summary>
+        /// Test FileUtils.IsValidGuid() when it returns true
+        /// </summary>
+        [Test]
+        public void IsValidGuid_TrueCases() {
+            Assert.That(
+                FileUtils.IsValidGuid("4b7c4a82-79ca-4eb5-a154-5d78a3b3d3d7"),
+                Is.EqualTo(true));
+
+            Assert.That(
+                FileUtils.IsValidGuid("017885d9f22374a53844077ede0ccda6"),
+                Is.EqualTo(true));
+        }
+
+        /// <summary>
+        /// Test FileUtils.IsValidGuid() when it returns false
+        /// </summary>
+        [Test]
+        public void IsValidGuid_FalseCases() {
+            Assert.That(
+                FileUtils.IsValidGuid(""),
+                Is.EqualTo(false));
+            Assert.That(
+                FileUtils.IsValidGuid(null),
+                Is.EqualTo(false));
+            Assert.That(
+                FileUtils.IsValidGuid("00000000-0000-0000-0000-000000000000"),
+                Is.EqualTo(false));
+            Assert.That(
+                FileUtils.IsValidGuid("00000000000000000000000000000000"),
+                Is.EqualTo(false));
+            Assert.That(
+                FileUtils.IsValidGuid("g000000000000000000000000000000"),
+                Is.EqualTo(false));
+            Assert.That(
+                FileUtils.IsValidGuid("   "),
+                Is.EqualTo(false));
+            Assert.That(
+                FileUtils.IsValidGuid("12300000 0000 0000 0000 000000000000"),
+                Is.EqualTo(false));
+            Assert.That(
+                FileUtils.IsValidGuid("12300000\n0000\n0000\n0000\n000000000000"),
+                Is.EqualTo(false));
+        }
     }
 }