Logging - callback function of log.error not called

[CodingGazelles]

I noticed that calls to log.error and log.write don't behave the same when it comes to execute the callback functions.

While I was trying to log an error thrown by my Datastore, I realized that my log.error callback was never executed. See code below.

• err is an error thrown by Datastore
• Trying to log err throws another error (Value of type object not recognized. at Function.GrpcService.encodeValue)
• This 2nd error should be catched by the callback, unfortunatly it is never the case with log.error
• But it works with log.write

const entry = log.entry (metadata, {
	error: "UnableToUpdateUser",
	data: {
		error: err
	}
})

log.error (entry)
	.then ( function (resp) {
		// fine 
	})
	.catch ( (logErr) => {
		// never called, this log never appears in Stackdriver
		log.error (log.entry (metadata, { error: "LogError 1"}))
	})


log.write (entry)
	.then ( function (resp) {
		// fine
	})
	.catch ( (logErr) => {
		// this one is called, can see it in Stackdriver
		log.error (log.entry (metadata, { error: "LogError 2"}))
	})

This was produced on the Google Function Emulator.

"@google-cloud/datastore": "^0.6.0",
"@google-cloud/logging": "^0.6.0"

gcloud -v :
Google Cloud SDK 138.0.0
alpha 2016.01.12
beta 2016.01.12
bq 2.0.24
bq-nix 2.0.24
cloud-datastore-emulator 1.2.1
core 2016.12.09
core-nix 2016.11.07
gcd-emulator v1beta3-1.0.0
gcloud 
gsutil 4.22
gsutil-nix 4.21

[bjwatson]

@stephenplusplus Is this expected behavior, or is there a bug here?

[stephenplusplus]

@t4ncr3d3 sorry for the delay. I believe the issue can be boiled down to a circular reference that the Datastore error had. Our code throws if it receives data that it cannot serialize. I've put together a PR that will change it from throwing to returning the error in the callback / promise error handler: #2081