Logger does not include jsonPayload if object property value is undefined

[willbattel]

[REQUIRED] Version info

node: 16.14.2

firebase-functions: 4.0.1

firebase-tools: 11.15.0

firebase-admin: 11.2.0

[REQUIRED] Test case

export const someFunction = functions.https.onRequest(async (req, res) => {
    functions.logger.error('Error 1', {
        foo: 'bar',
    }
    functions.logger.error('Error 2', {
        foo: null,
    }
    functions.logger.error('Error 3', {
        foo: undefined,
    }
    res.status(200).send()
})

[REQUIRED] Steps to reproduce

Deploy and call any type of cloud function, http or other, and log an error with a message and an object containing a property with a value of undefined.

[REQUIRED] Expected behavior

We expect the jsonPayload to describe the object properties in every above case, including when the object property is undefined.

[REQUIRED] Actual behavior

Log 1

jsonPayload: {
 foo: "bar"
 message: "Error 1 <stack>"
}

Log 2

jsonPayload: {
 foo: null
 message: "Error 2 <stack>"
}

Log 3

textPayload: "Error 3 <stack>"

Log 3 does not include jsonPayload. We want it to specify foo: undefined, as that is important information to us.

Were you able to successfully deploy your functions?

Yes, there are no issues with deployment.

[inlined]

There is no such thing as undefined in JSON. What results were you expecting?

[willbattel]

I'm not 100% sure what the best solution would be, but the fact that jsonPayload was missing entirely was very confusing before I discovered the property value was undefined. I know having a string value of "undefined" would potentially have its own problems but I have to think there is a better solution than omission of the entire payload.