classIdPresentInChange should be true when ecClassId is present

common/changes/@itwin/core-backend/nick-changesetecadaptor-fixmaybe_2024-01-04-21-23.json

@@ -0,0 +1,10 @@
+{
+  "changes": [
+    {
+      "packageName": "@itwin/core-backend",
+      "comment": "",
+      "type": "none"
+    }
+  ],
+  "packageName": "@itwin/core-backend"
+}

core/backend/src/ChangesetECAdaptor.ts

@@ -408,6 +408,44 @@ namespace DateTime {
 export class PartialECChangeUnifier {
   private _cache = new Map<string, ChangedECInstance>();
   private _readonly = false;
+  /**
+   * Get root class id for a given class
+   * @param classId given class id
+   * @param db use to find root class
+   * @returns return root class id
+   */
+  private static getRootClassId(classId: Id64String, db: AnyDb): Id64String | undefined {
+    const sql = `
+      WITH
+      [base_class]([classId], [baseClassId], [Level]) AS(
+        SELECT [ch].[ClassId], [ch].[BaseClassId], 0
+        FROM   [ec_ClassHasBaseClasses] [ch] WHERE  [ch].[ClassId] = ?
+        UNION ALL
+        SELECT [ch].[ClassId], [ch].[BaseClassId], [Level] + 1
+        FROM   [ec_ClassHasBaseClasses] [ch], [base_class] [bc] WHERE  [bc].[BaseClassId] = [ch].[ClassId]
+
+      )
+      SELECT FORMAT('0x%x', [bc].[BaseClassId]) rootClass
+      FROM   [base_class] [bc]
+      WHERE  [bc].[ClassId] <> [bc].[BaseClassId]
+              AND [bc].[BaseClassId] NOT IN (SELECT [ca].[ContainerId]
+            FROM   [ec_CustomAttribute] [ca]
+            WHERE  [ca].[ContainerType] = 30
+                      AND [ca].[ClassId] IN (SELECT [cc].[Id]
+                    FROM   [ec_Class] [cc]
+                          JOIN [ec_Schema] [ss] ON [ss].[Id] = [cc].[SchemaId]
+                    WHERE  [cc].[Name] = 'IsMixIn'
+                            AND [ss].[Name] = 'CoreCustomAttributes'))
+      ORDER BY [Level] DESC`;
+
+    return db.withSqliteStatement(sql, (stmt) => {
+      stmt.bindId(1, classId);
+      if (stmt.step() === DbResult.BE_SQLITE_ROW && !stmt.isValueNull(0)) {
+        return stmt.getValueString(0);
+      }
+      return classId;
+    });
+  }
   /**
    * Combine partial instance with instance with same key if already exists.
    * @param rhs partial instance
@@ -416,7 +454,7 @@ export class PartialECChangeUnifier {
     if (!rhs.$meta) {
       throw new Error("PartialECChange being combine must have '$meta' property");
     }
-    const key = PartialECChangeUnifier.buildKey(rhs);
+    const key = PartialECChangeUnifier.buildKey(rhs, db);
     const lhs = this._cache.get(key);
     if (lhs) {
       const { $meta: _, ...restOfRhs } = rhs;
@@ -450,8 +488,17 @@ export class PartialECChangeUnifier {
    * @param change EC change
    * @returns key created from EC change.
    */
-  private static buildKey(change: ChangedECInstance): string {
-    return `${change.ECClassId}-${change.ECInstanceId}-${change.$meta?.stage}`.toLowerCase();
+  private static buildKey(change: ChangedECInstance, db?: AnyDb): string {
+    let classId = change.ECClassId;
+    if (typeof classId === "undefined") {
+      if (db && change.$meta?.fallbackClassId) {
+        classId = this.getRootClassId(change.$meta.fallbackClassId, db);
+      }
+      if (typeof classId === "undefined") {
+        throw new Error(`unable to resolve ECClassId to root class id.`);
+      }
+    }
+    return `${change.ECInstanceId}-${classId}-${change.$meta?.stage}`.toLowerCase();
   }
   /**
    * Append partial changes which will be combine using there instance key.
@@ -711,7 +758,7 @@ export class ChangesetECAdaptor implements IDisposable {
         }
 
         let ecClassId: Id64String | undefined = this.reader.op === "Inserted" ? change.inserted?.ECClassId : change.deleted?.ECClassId;
-        const classIdPresentInChange = !ecClassId;
+        const classIdPresentInChange = typeof ecClassId !== "undefined";
         let classMap: IClassMap | undefined;
         let fallbackClassId: Id64String | undefined;
         if (table.isClassIdVirtual) {
@@ -737,7 +784,7 @@ export class ChangesetECAdaptor implements IDisposable {
         if (!classMap)
           throw new Error(`unable to load class map`);
 
-        if (!classIdPresentInChange && !ecClassId)
+        if (!classIdPresentInChange && !ecClassId && !fallbackClassId)
           ecClassId = classMap.id;
 
         if (this._allowedClasses.size !== 0) {