Got descriptors for a characteristic we don't know about

[vyeevani]

Describe the bug
"Got descriptors for a characteristic we don't know" about while connecting to an iRobot Create 3.

Expected behavior
able to connect to peripheral

Actual behavior
the connect fails with error: "Got descriptors for a characteristic we don't know"

Additional context
error is coming from:
pub fn set_characteristic_descriptors(
&mut self,
service_uuid: Uuid,
characteristic_uuid: Uuid,
descriptors: HashMap<Uuid, StrongPtr>,
) {
in corebluetooth internal

[vyeevani]

Seeing the following sequence of events:
delegate_peripheral_diddiscovercharacteristicsforservice_error CBPeripheral(iRobotCreate3, 6F18E7F1-76E0-F57F-4A46-E588ED87545A) CBService(180A)
delegate_peripheral_diddiscoverincludedservicesforservice_error CBPeripheral(iRobotCreate3, 6F18E7F1-76E0-F57F-4A46-E588ED87545A) CBService(180A)
delegate_peripheral_diddiscovercharacteristicsforservice_error CBPeripheral(iRobotCreate3, 6F18E7F1-76E0-F57F-4A46-E588ED87545A) CBService(180A)
delegate_peripheral_diddiscoverincludedservicesforservice_error CBPeripheral(iRobotCreate3, 6F18E7F1-76E0-F57F-4A46-E588ED87545A) CBService(180A)
delegate_peripheral_diddiscovercharacteristicsforservice_error CBPeripheral(iRobotCreate3, 6F18E7F1-76E0-F57F-4A46-E588ED87545A) CBService(48C5D828-AC2A-442D-97A3-0C9822B04979)
delegate_peripheral_diddiscoverincludedservicesforservice_error CBPeripheral(iRobotCreate3, 6F18E7F1-76E0-F57F-4A46-E588ED87545A) CBService(48C5D828-AC2A-442D-97A3-0C9822B04979)
delegate_peripheral_diddiscovercharacteristicsforservice_error CBPeripheral(iRobotCreate3, 6F18E7F1-76E0-F57F-4A46-E588ED87545A) CBService(6E400001-B5A3-F393-E0A9-E50E24DCCA9E)
delegate_peripheral_diddiscoverincludedservicesforservice_error CBPeripheral(iRobotCreate3, 6F18E7F1-76E0-F57F-4A46-E588ED87545A) CBService(6E400001-B5A3-F393-E0A9-E50E24DCCA9E)
delegate_peripheral_diddiscoverdescriptorsforcharacteristic_error CBPeripheral(iRobotCreate3, 6F18E7F1-76E0-F57F-4A46-E588ED87545A) CBCharacteristic(2A50)
delegate_peripheral_diddiscoverdescriptorsforcharacteristic_error CBPeripheral(iRobotCreate3, 6F18E7F1-76E0-F57F-4A46-E588ED87545A) CBCharacteristic(8BB6)
Found descriptors for peripheral 6f18e7f1-76e0-f57f-4a46-e588ed87545a service 0000180a-0000-1000-8000-00805f9b34fb characteristic 00002a50-0000-1000-8000-00805f9b34fb:
delegate_peripheral_diddiscoverdescriptorsforcharacteristic_error CBPeripheral(iRobotCreate3, 6F18E7F1-76E0-F57F-4A46-E588ED87545A) CBCharacteristic(2A26)
Failed to get characteristic with UUID: 00002a50-0000-1000-8000-00805f9b34fb for service UUID: 0000180a-0000-1000-8000-00805f9b34fb

Still trying to work out what the uuid conversions are here.

I should also mention I'm on the latest macOS 15.1 developer beta. Not sure if that has some bluetooth bugs or mb the uuid conversion scheme has changed in the latest os?

[vyeevani]

It seems that: set_characteristics will overwrite all the prior characteristics of the service which may not be the right behavior here. If not overwriting all prior characteristics is the desired behavior, then there is a race condition between the characteristic storage and descriptor storage.

[vyeevani]

I ended up doing this for both the set_characteristics and set_characteristic_descriptors because it seemed like both had the same style of overwrite behavior.

pub fn set_characteristics(
        &mut self,
        service_uuid: Uuid,
        characteristics: HashMap<Uuid, StrongPtr>,
    ) {
        let service = self
            .services
            .get_mut(&service_uuid)
            .expect("Got characteristics for a service we don't know about");
        
        for (characteristic_uuid, characteristic) in characteristics {
            service.characteristics.insert(characteristic_uuid, CBCharacteristic::new(characteristic));
        }

        if service.characteristics.is_empty() {
            service.discovered = true;
            self.check_discovered();
        }
    }

    pub fn set_characteristic_descriptors(
        &mut self,
        service_uuid: Uuid,
        characteristic_uuid: Uuid,
        new_descriptors: HashMap<Uuid, StrongPtr>,
    ) {
        let service = self
            .services
            .get_mut(&service_uuid)
            .expect("Got descriptors for a service we don't know about");
        let characteristic = service
            .characteristics
            .get_mut(&characteristic_uuid)
            .expect("Got descriptors for a characteristic we don't know about");

        for (descriptor_uuid, descriptor) in new_descriptors {
            characteristic
                .descriptors
                .entry(descriptor_uuid)
                .or_insert_with(|| CBDescriptor::new(descriptor));
        }
        characteristic.discovered = true;

        if !service
            .characteristics
            .values()
            .any(|characteristic| !characteristic.discovered)
        {
            service.discovered = true;
            self.check_discovered()
        }
    }