Manual Trigger Link for Apollo GraphQL Client

An ApolloLink to trigger data coming manually.

Why?

To have a simulation of GraphQL Subscription events in client-side mocks, runnable from your browser console.

Installation

yarn add @quiqup/manual-trigger-link

Peer dependencies

• apollo-link

Usage

NB! See also:

• About Apollo Schema Link
• About GraphQL Mocking

1. Use it in your mock client

You it in your mock client and pass a setTrigger function.

...
const link = ApolloLink.split(
  hasSubscription,
  ApolloLink.from([new ManualTriggerLink({ setTriggers }), schemaLink]),
  schemaLink
)
const cache = new InMemoryCache()
return new ApolloClient({ cache, link })

setTriggers function can be called several times during execution and will receive one parameter - an object with the following shape:

{
  _all, // Triggers updates on all subscriptions
  _inspect, // Returns an object with all current subscriptions
  [operationName], // A set of functions to trigger updates based on operationName (e.g. `task` for gql`subscription task {...}`)
}

Example of setTriggers func implementation:

const setTriggers = triggers => {
  if (!window.mocks) window.mocks = {}
  window.mocks.triggers = triggers
})

2. Setup your mock client

Set up your mock client by setting SchemaLink parameters, like rootValue or mocks.

Operation triggers can accept a context object which will be passed to your resolvers. In this example we can configure whether we want a normal task or an empty update (say, the task is unassigned from COR):

// This root value will be passed to SchemaLink
const rootValue = {
  task: (root, variables, context) => {
    const { empty } = context || {}
    return empty ? null : mockTaskObject
  },
}

3. User your mock client in your app

We recommend putting all mocking stuff under a dynamic import and not using it in production. For example, in dev environment there's a function like that, assigned to a window object:

mocksOn = async () => {
  const mockClientModule = await import('./get-mock-client')
  const client = await mockClientModule.default(getClientOptions(), triggers => {
    window.mocks.triggers = triggers
  })
}

4. Call mocks from dev console

So now you can call your mocks from browser's dev console:

mock.triggers.new() // for normal task mock
mock.triggers.new({ empty: true }) // to get an update with `null` as data

NB! There's an issue with apollo-link-state: it doesn't work with subscriptions. Inside, it closes all internal Observers' subscriptions objects, so you can't get new data. That's why for mock-client you should have apollo-link-state only for normal queries and mutations. This means that for now you can't use client resolvers for subscriptions. Please see this issue: https://github.com/apollographql/apollo-link-state/issues/138

Acknowledgements

Bootstrapped with generator-quiqup-lib

License

MIT © Quiqup