AppSync event looks like a map and not like AppSyncResolverTemplate

[sashker]

Hello.

I'm awaiting events.AppSyncResolverTemplate having all usual fields like Operation, Version, Payload from AppSync.

My mapping template produced from the original Invoke and forward arguments

{
    "version" : "2017-02-28",
    "operation": "Invoke",
    "payload": $util.toJson($context.arguments)
}

I thought I have to recieve a JSON with all those fields. But when I eventually decided to specify an event like an interface{} it turned out that I recieve a map[] of values

map[input:map[someField:1922 locationCountry:US]]

Can somebody clarify, please, if it works as expected or not?

[daviskoh]

I can confirm this

mapping template:

{
  "version": "2017-02-28",
  "operation": "Invoke",
  "payload": {
    "field": "correctField",
    "arguments":  $utils.toJson($context.arguments)
  }
}

func(event events.AppSyncResolverTemplate) error {
...
}

does not populate event. Logging event will output:

{ []}

Edit 1:

Following the README format with:

func(ctx context.Context, event events.AppSyncResolverTemplate) error {
...
}

populates ctx, but again event is an empty { []}

Edit 2:

Doesn't seem to be like events.APIGatewayProxyRequest either this guy is suggesting...

func(req events.APIGatewayProxyRequest) error {
...
}

Printing req outputs:

{ map[] map[] map[] map[] map[] map[] { { } map[] } false}

Edit 3:

Also tried changing the mapping template:

{
  "version": "2017-02-28",
  "operation": "Invoke",
  "payload": $utils.toJson($context.arguments)
}

and get the same results.

Are Go handlers for AppSync just not supported? This issue makes them unusable. Documentation only exists for NodeJS, so maybe the inclusion of AppSyncResolverTemplate is just a preview as Go is not actually supported for AppSync? What are the actual valid arg types for Handler?

[daviskoh]

Are there any updates on this? This issue has been open for a few months...

[daviskoh]

@sashker did you figure out this issue?

[daviskoh]

I managed to get everything working. My mistake was a misunderstanding of what exactly is passed into the Handlers.

AppSyncResolverTemplate is not what is passed in. Rather, what is defined as the payload field in the mapping template is what is passed into the Handler.

For ex:

mapping template:

{
  "version": "2017-02-28",
  "operation": "Invoke",
  "payload": $utils.toJson($context.args) // <-- note this is args not arguments
}

sample query:

query Post {
  singlePost(id: "meowww") {
    id
  }
}

Type:

type Post {
  Id string `json:"id"` // tags are required if you plan on reusing the type as a response as well
}

Handler:

func Handler(post Post) (Post, error) {
  ...
}

I'm unsubscribing to this thread. @ me if u have any questions.

[cduggn]

@daviskoh I think the map type might be more flexible in these situations. Map can adjust to new arguments being added, and usage can be replicated across other handlers. The strict format of the struct you mentioned above will also work, just not as flexible

type Event struct {
	Arguments map[string]string `json:"arguments"`
	Field     string            `json:"field"`
}

func HandleRequest(ctx context.Context, e Event) (string, error) {`
        id := e.Arguments["id"]
	fmt.Println("id: ", id)