Registering multiple event listeners on the same event does not work

[i124q2n8]

Issue Summary

Using on / addListener multiple times with the same event name does not fire any of the attached listeners. This seems to be true for all events that use the Register*Callback function from database.cc. I will use on('change') as an example.

This is due to the way the Database::Register*Callback functions are implemented:

void Database::RegisterUpdateCallback(Baton* b) {
    std::unique_ptr<Baton> baton(b);
    assert(baton->db->open);
    assert(baton->db->_handle);
    Database* db = baton->db;

    if (db->update_event == NULL) {
        // Add it.
        db->update_event = new AsyncUpdate(db, UpdateCallback);
        sqlite3_update_hook(db->_handle, UpdateCallback, db);
    }
    else {
        // Remove it.
        sqlite3_update_hook(db->_handle, NULL, NULL);
        db->update_event->finish();
        db->update_event = NULL;
    }
}

Calling on('change', ...) will invoke this function which will eventually call Database::RegisterUpdateCallback.
The first call to on('change', ...) will register the Database::UpdateCallback. The seconds call will remove it. The third call will register the callback again.

Fix:

• db.configure / Database::Configure is called with a second argument that states whether the callback should be registered or removed. This argument is not passed to Database::Register*Callback.

Note: Calling on('change', ...) an odd number of times will lead to the correct behavior.

Steps to Reproduce

You can use this example code to reproduce the error.

const db = new Database(':memory:');
db.on('change', () => { console.log ('listener 1')});
db.on('change', () => { console.log ('listener 2')});
//Uncomment next to see all listeners
//db.on('change', () => { console.log ('listener 3')});
db.exec(`
  CREATE TABLE "test" (
    name TEXT
  )
`, () => {
  db.exec(`
    INSERT INTO "test" (
      name
    ) VALUES (
      'test'
    )
  `)
});

Version

^5.1.2

Node.js Version

v18.2.0

How did you install the library?

Does not apply

[little-brother]

Also there is no doc about it :(