IssueTracker

Component used: Room
Version used: 2.1.0-alpha01
Devices/Android versions reproduced on: Nexus 5 (Android 6.0.1) and Emulator (Android 8)
Android Studio 3.3 Canary 13

I create this DAO

import androidx.room.*
import dominando.android.data_room.entity.Book
import io.reactivex.Completable
import io.reactivex.Flowable
import io.reactivex.Maybe

@Dao
interface BookDao {
    @Insert(onConflict = OnConflictStrategy.REPLACE)
    fun save(book: Book): Completable

    @Delete
    fun delete(vararg book: Book): Completable

    @Query("SELECT * FROM Book WHERE title LIKE :title ORDER BY title")
    fun bookByTitle(title: String = "%"): Flowable<List<Book>>

    @Query("SELECT * FROM Book WHERE id = :id")
    fun bookById(id: String): Maybe<Book>
}

But compilation fails with this error.

error: local variable book is accessed from within inner class; needs to be declared final

When I look to the generated code, this is it.

  @Override
  public Completable save(Book book) {
    return Completable.fromCallable(new Callable() {
      @Override
      public Void call() throws Exception {
        __db.beginTransaction();
        try {
          __insertionAdapterOfBook.insert(book);
          __db.setTransactionSuccessful();
          return null;
        } finally {
          __db.endTransaction();
        }
      }
    });
  }

As you can see, book parameter is not marked as final and cannot be accessed inside of Completable.fromCallable.