I just realized the code I wrote is a modification to the compiled output, not the original source. Recommend closing this PR and having someone who actually has the project checked out locally applying the fix.

Okay, this should not happen, how exactly are errors getting swallowed though? I might want to implement a try/catch in the meantime if that is the case. @MicahZoltu

Not sure if it helps, but I am getting an UnhandledPromiseRejectionWarning every time something fails with rpc @SilentCicero

node-server_1  | (node:28) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): Error: [ethjs-rpc]  error with payload {"id":2575583708953,"jsonrpc":"2.0","params":[{"to":"0xA97fEfe489ca62ADD4949360DCE30e3351F6881B","data":"0x8eaa6ac01201cf23b4c1d237a7c146584a8e540995f700cf38525cf627cc3407eac17416"},"latest"],"method":"eth_call"} Error: [ethjs-provider-http] Invalid JSON RPC response from provider
node-server_1  |     host: https://rinkeby.infura.io/ywCD9mvUruQeYcZcyghk
node-server_1  |     response:  ""
node-server_1  |     responseURL: undefined
node-server_1  |     status: 0
node-server_1  |     statusText:
node-server_1  |
node-server_1  | (node:28) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

And the actual error message never made it out to my server code, where I can actually try to handle it

Just a simple get() of a smart contract deployed in rinkeby
https://github.com/likecoin/likecoin-poc/blob/master/server.js#L155
It fails randomly but I was never able to debug it, due to the error message being empty like above

@williamchong007 Upgrade to the latest version of ethjs-query/ethjs-rpc. It resolves the null error message issue, allowing you to actually debug your code. :)

@SilentCicero I don't use ethjs-contract anymore, but the problem still occurs with ethjs-query and I believe it has the same root cause. To reproduce the problem, cause the JSON-RPC return a JSON-RPC error when calling await this.connector.ethjsQuery.estimateGas(transaction);. This should result in the rejected promise turning into a node exception here due to the await call which can then be wrapped in a try/catch. However, instead what happens is node screams about an unhandled promise rejection. This is because (I believe) that a promise is being generated by one of the lower level libraries but a callback is being used to detect the error instead of the promise.

The fundamental issue here is that if you instantiate a Promise in node, you must hookup a .catch to it OR await it. Throughout the ethjs codebase there is a weird mix of promises + callbacks. If someone uses callbacks to monitor for failure, they will not hookup a .catch to the Promise which means they'll get an unhandled promise rejection error from node. I strongly recommend removing support for callbacks and just using promises. If someone really wants, they can create a wrapper that turns the promise into a callback, but in a way that appropriately sets up the .then and .catch. I believe there are even libraries that do this automatically for you.

I dived into my local docker-compose container and checked the ethjs version,
and above UnhandledPromiseRejectionWarning still happen @0.3.1

Interestingly it does not seems to happen at all, when I deploy the same container onto production k8s

I don't know if this is a good workaround, but I commented out "reject(callbackError)" from line 8350 and then I could catch the exception without having any problem with unhandled exception.

if (callbackError) {
    //reject(callbackError);
    protoCallback(callbackError, null);

this was resolved! 😸