Types on onCompleted incomplete, should include undefined

[ghost]

Intended outcome:

As far as I understand the onCompleted callback is being triggered when a query has finished loading independent of whether there was any data returned or not (e.g. in an error case). This means it is possible to call the callback with data set to undefined.

Therefore the typing should probably be:

onCompleted?: (data: TData | undefined) => void;

Actual outcome:

The current typings are:

onCompleted?: (data: TData) => void;

making it easy to forget handling the undefined-case in the code.

How to reproduce the issue:

n/a I think but would be happy to make something up if people think it's useful.

Version

  System:
    OS: macOS Mojave 10.14.6
  Binaries:
    Node: 12.10.0 - /usr/local/bin/node
    Yarn: 1.16.0 - ~/1-work-projects/app/node_modules/.bin/yarn
    npm: 6.11.3 - /usr/local/bin/npm
  Browsers:
    Chrome: 77.0.3865.90
    Firefox: 69.0.1
    Safari: 13.0.1
  npmPackages:
    @apollo/react-testing: ^3.1.0 => 3.1.0 
    apollo: 2.12.0 => 2.12.0 
    apollo-cache-inmemory: ^1.6.2 => 1.6.2 
    apollo-client: ^2.6.4 => 2.6.4 
    apollo-link: ^1.2.12 => 1.2.12 
    apollo-link-error: ^1.1.11 => 1.1.11 
    apollo-link-http: ^1.5.15 => 1.5.15 
    react-apollo: ^3.1.0 => 3.1.0