Possible Unhandled Promise Rejection (id: 0). How to handle these warnings? Where do they come from?

Intended outcome:

I can’t tell where and why warning is thrown in the code.

Actual outcome:

Stacktrace is absolutely cryptic. No chances to understand why and where warning is thrown.

What is The provided key element? What schema is does this warning says about? Mutation has two of them: UpdateMutation and GetQuery? Which one?

    this.props.client.mutate({
      mutation: UpdateMutation,
      refetchQueries: [{ query: GetQuery }],

Can you tell me where this warning happened?

Does your Apollo have means to show where this warning is thrown?

This happens after mutation.

Versions

  System:
    OS: macOS High Sierra 10.13.4
  Binaries:
    Node: 8.11.3 - /usr/local/bin/node
    npm: 5.6.0 - /usr/local/bin/npm
  Browsers:
    Chrome: 68.0.3440.106
    Safari: 11.1
  npmPackages:
    apollo-boost: ^0.1.4 => 0.1.10 
    apollo-cache-inmemory: ^1.1.0 => 1.2.5 
    apollo-client: ^2.0.3 => 2.3.5 
    apollo-link: ^1.0.3 => 1.2.2 
    apollo-link-http: ^1.2.0 => 1.5.4 
    react-apollo: ^2.1.1 => 2.1.9

Similar issue https://github.com/apollographql/apollo-client/issues/3858 Same https://github.com/apollographql/apollo-client/issues/431 Same https://github.com/apollographql/apollo-client/issues/423

[mlarcher]

This issue is still there with 2.6.8 !

Code is working fine, but tests crash with cryptic message.

Adding a .catch() call after the mutation call is working fine, but feels like a gross hack.

Any chance to get this handled in the module ? As @joelgetaction stated, we shouldn’t get a rejected promise there, as it is already handled and the error is available from the useMutation error field to deal with !

Here is the output when testing the module with Jest and react-testing-library:

/Users/somatt/www/hm/_hm/app/client/node_modules/react-dom/cjs/react-dom.development.js:302
      var evt = document.createEvent('Event'); // Keeps track of whether the user-provided callback threw an error. We
                         ^

TypeError: Cannot read property 'createEvent' of null
    at Object.invokeGuardedCallbackDev (/Users/somatt/www/hm/_hm/app/client/node_modules/react-dom/cjs/react-dom.development.js:302:26)
    at invokeGuardedCallback (/Users/somatt/www/hm/_hm/app/client/node_modules/react-dom/cjs/react-dom.development.js:440:31)
    at flushPassiveEffectsImpl (/Users/somatt/www/hm/_hm/app/client/node_modules/react-dom/cjs/react-dom.development.js:25350:7)
    at unstable_runWithPriority (/Users/somatt/www/hm/_hm/app/client/node_modules/scheduler/cjs/scheduler.development.js:818:12)
    at runWithPriority$2 (/Users/somatt/www/hm/_hm/app/client/node_modules/react-dom/cjs/react-dom.development.js:12130:10)
    at flushPassiveEffects (/Users/somatt/www/hm/_hm/app/client/node_modules/react-dom/cjs/react-dom.development.js:25319:12)
    at Object.<anonymous>.flushWork (/Users/somatt/www/hm/_hm/app/client/node_modules/react-dom/cjs/react-dom-test-utils.development.js:1039:10)
    at Immediate.<anonymous> (/Users/somatt/www/hm/_hm/app/client/node_modules/react-dom/cjs/react-dom-test-utils.development.js:1050:11)
    at processImmediate (internal/timers.js:439:21)
(node:28822) UnhandledPromiseRejectionWarning: TypeError: Caught error after test environment was torn down

Cannot read property 'createEvent' of null
(node:28822) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 2)
(node:28822) [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.

This error breaks all the test suite, which crashes on that output.

[nedgar]

this is a violation of the principle of least surprise

I have to agree. With react-apollo ^2.3.2 I’m able to avoid this by giving a dummy function to Mutation’s onError prop, e.g.

        <Mutation
          mutation={MUMUMUMYMUTATION}
          variables={{...}}
          onError={err => null} // handled below
        >