Android Room KSP可空性处理异常问题咨询

我的Android应用中有如下Room DAO函数：

@RawQuery
@Transaction
abstract suspend fun queryOneOrNone(query: SupportSQLiteQuery): TEntity?

kapt生成的Java代码如下：

@Override
public Object queryOneOrNone(final SupportSQLiteQuery query,
    final Continuation<? super MyEntity> $completion) {
  final CancellationSignal _cancellationSignal = DBUtil.createCancellationSignal();
  return CoroutinesRoom.execute(__db, true, _cancellationSignal, new Callable<MyEntity>() {
    @Override
    @Nullable
    public MyEntity call() throws Exception {
      __db.beginTransaction();
      try {
        final Cursor _cursor = DBUtil.query(__db, query, false, null);
        try {
          final MyEntity _result;
          if (_cursor.moveToFirst()) {
            _result = __entityCursorConverter_persistenceStorageMyEntity(_cursor);
          } else {
            _result = null;
          }
          __db.setTransactionSuccessful();
          return _result;
        } finally {
          _cursor.close();
        }
      } finally {
        __db.endTransaction();
      }
    }
  }, $completion);
}

而KSP生成的代码如下：

public override suspend fun queryOneOrNone(query: SupportSQLiteQuery):
    MyEntity? {
  val _cancellationSignal: CancellationSignal? = createCancellationSignal()
  return execute(__db, true, _cancellationSignal, object :
      Callable<MyEntity?> {
    public override fun call(): MyEntity? {
      __db.beginTransaction()
      try {
        val _cursor: Cursor = query(__db, query, false, null)
        try {
          val _result: MyEntity
          if (_cursor.moveToFirst()) {
            _result =
                __entityCursorConverter_persistenceStorageMyEntity(_cursor)
          } else {
            error("The query result was empty, but expected a single row to return a NON-NULL object of type <MyEntity>.")
          }
          __db.setTransactionSuccessful()
          return _result
        } finally {
          _cursor.close()
        }
      } finally {
        __db.endTransaction()
      }
    }
  })
}

应用运行时抛出错误：

"The query result was empty, but expected a single row to return a NON-NULL object of type <MyEntity>."

目前我可以通过在Gradle中添加如下配置缓解问题，但更希望保留KSP生成Kotlin代码的功能：

ksp {
    arg("room.generateKotlin", "false")
}

请问这是KSP的问题，还是我的应用代码存在错误？

这是Room KSP处理器的bug，和你的应用代码无关。

从代码对比可以明确看出：

• kapt生成的代码正确适配了可空返回类型TEntity?：当查询无结果时返回null
• KSP生成的代码存在逻辑错误：尽管返回类型标注为可空的MyEntity?，但在查询无结果时却调用error()抛出异常，而非返回null

解决办法：

1. 升级Room版本：该bug在Room 2.5.0及后续版本中已被修复，建议直接升级Room依赖到对应版本
2. 临时替代方案：如果暂时无法升级，可继续使用你提到的Gradle配置room.generateKotlin=false，让KSP生成Java代码以规避该bug

内容的提问来源于stack exchange，提问作者Hector