Improve error messages that are returned when an exception is thrown while attempting to subscribe in JS

Describe the feature

Description

When using the subscribe() method in a JavaScript application (ReactJS), if the method gets a QoS parameter that is of type string, it throws an exception with an empty error message. This makes it difficult to debug the issue.

For instance:

The HTML radio input always returns a value of type string, regardless of what value type you specify. This is the react component I used:

const QualityOfService = (props) => {
    return (
        <RadioGroupField label="Quality of Service" name={props.name} onChange={props.onChange} defaultValue={mqtt.QoS.AtMostOnce}>
            <Radio value={mqtt.QoS.AtMostOnce}>Quality of Service 0 - Message will be delivered at most once</Radio>
            <Radio value={mqtt.QoS.AtLeastOnce}>Quality of Service 1 - Message will be delivered at least once</Radio>
        </RadioGroupField>
    );
}

Hence, the code below returns an error with message, There is something wrong with the subscription: {} and there is no subscribe event seen in AWS IoT Core's CloudWatch logs:

// Trigger topic subscription
    const subscribeHandler = (event) => {
        event.preventDefault();

        let temporarySubscriptionObject = { 'topic': '', 'qosLevel': null };
        temporarySubscriptionObject.topic = topic;
        temporarySubscriptionObject.qosLevel = qosLevel;

        setSubscriptionObjects(prevSubscriptions => [...prevSubscriptions, temporarySubscriptionObject]);
    };

console.log(`Subscribing to ${subscriptionObject.topic} with QoS type ${typeof subscriptionObject.qosLevel} ...`);
async function beginSubscription(connection) {
                try {
                    let returnedSubscription = await connection.subscribe(
                        subscriptionObject.topic,
                        subscriptionObject.qosLevel,
                        (topic, payload, dup, qos, retain) => {
                            const decoder = new TextDecoder("utf8");
                            let message = decoder.decode(new Uint8Array(payload));

                            console.log(`Message received: topic=${topic} message=${message}`);

                            setMessageobjects(prevMessageObjects => [...prevMessageObjects, { 'topic': topic, 'message': message }]);
                        })

                    console.log(`Checking that the subscribe is working: ${JSON.stringify(returnedSubscription)}`);
                } catch (error) {
                    console.log(`There is something wrong with the subscription: ${JSON.stringify(error)}`);
                }

            }

Use Case

I need this for scenarios where I'm developing an application in JavaScript, and not TypeScript.

Proposed Solution

Validate type of the QoS value, before subscribing.

Other Information

No response

Acknowledgements

[X] I may be able to implement this feature request
[ ] This feature might incur a breaking change

awslabs / aws-crt-nodejs