Crash in -[RZBPeripheral cancelAllCommands] due to infinite loop

[joshuatbrown]

Issue

In the completion block of -[RZBPeripheral connectWithCompletion:], call -[RZBPeripheral cancelConnectionWithCompletion:]. It'll create an infinite loop and eventually crash with an EXC_BAD_ACCESS.

For example:

- (void)testCancelConnectionInConnectCompletion {
    RZBPeripheral *peripheral = [self.centralManager peripheralForUUID:self.connection.identifier];

    [peripheral connectWithCompletion:^(NSError * _Nullable error) {
        [peripheral cancelConnectionWithCompletion:nil];
    }];
    
    [self waitForQueueFlush];
}

[joshuatbrown]

Unfortunately, our fix for this causes a different RZBluetooth test to fail. Here's our fix in RZBPeripheral:

- (void)cancelAllCommands
{
    NSError *error = [NSError errorWithDomain:RZBluetoothErrorDomain
                                         code:RZBluetoothConnectionCancelled
                                     userInfo:@{}];

    NSArray *commands = self.dispatch.commands.copy;
    for (RZBCommand *command in commands) {
        if (command.isExecuted == YES && command.isCompleted == NO) {
            // We are in the completion handler of this command. Do not complete it or we will loop infinitely.
            continue;
        }

        [self.dispatch completeCommand:command
                            withObject:nil error:error];
    }
}

This fixes the test case above, but it causes -[RZBSimulatedTests testConnectionAndCancelWhileNotConnectable] to fail, and I'm not sure why. Can someone explain the purpose of that test and why it fails with this fix?

[cpatterson-lilly]

@joshuatbrown It seems that every access to RZBCommandDispatch.commands must be @synchronized.... Try replacing self.dispatch.commands.copy with a call to the (currently internal) method RZBDispatch.synchronizedCommandsCopy(), or wrapping that line in an @synchronized block?

[joshuatbrown]

@cpatterson-lilly I replaced my NSArray *commands = ... line above with the following:

NSArray *commands;
@synchronized(self.dispatch.commands) {
    commands = [self.dispatch.commands copy];
}

The same test still fails for the same reason. I can leave the @synchronized if that's the right way, but it looks like we still need to figure out how to make the test pass.

[joshuatbrown]

You can see my branch/commit above where I added the unit test and fixed the crash. But I'm still seeing the failure in -[RZBSimulatedTests testConnectionAndCancelWhileNotConnectable]. Any idea what's going on?