aws-appsync: Support DataSource type NONE

[christophgysin]

Currently aws-appsync only supports data source types AMAZON_DYNAMODB and AWS_LAMBDA. This is a request to add support for type NONE.

Use Case

To trigger GraphQL subscriptions from the backend, it's common to create a mutation that is triggerd by the backend. These don't necessarily need an actual datasource, and the AppSync data source type NONE can be used instead.

Proposed Solution

Add a new type NoneDataSource and a method GraphQLApi.addNoneDataSource().

Other

• 👋 I may be able to implement this feature request
• ⚠️ This feature might incur a breaking change

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This is a 🚀 Feature Request

[MrArnoldPalmer]

This makes sense. Do you have any examples we could see of this in use? Just want to understand the use-case a little better.

[christophgysin]

A simple use case for a NONE data source is any query that returns static data that is purely defined in VTL.

The use case described in the description above is about a way to send events from the server to the client without actually needing to invoke Lambda or DynamoDB. The schema defines a mutation and a subscription that uses @aws_subscribe() to subscribe to the mutation. The client calls the subscription, and the backend calls the mutation to trigger all subscribed clients.

See also:
https://docs.aws.amazon.com/appsync/latest/devguide/tutorial-local-resolvers.html

[MrArnoldPalmer]

awesome, I ran into those docs but your explanation helps. Checking out the PR.

[christophgysin]

fixed in #7145