AWS AppSync - DeleteItem doesn't execute response mapping template

Question

When attempting to delete an item using the following request mapping:

{
  "version" : "2017-02-28",
  "operation" : "DeleteItem",
  "key" : {
      "id": { "S" : "$ctx.args.id"},
      "sortKey" : { "S" : "$ctx.args.sortKey"}
  }
}

If the item exists it will process the result through the response template, however when the item does not exist the response template is never run.

Response template:

#set($ctx.result.status = "SUCCESS")
#set($ctx.result.message = "This was a success!")
$utils.toJson($ctx.result)

I am aware that when an item does not exist in Dynamo it will perform no action but I would expect that it would still process through the template.

Is there anything I am missing or is it impossible for AppSync to processed a DeleteItem request through the response mapping when the document does not exist?

Tinou Tinou · Accepted Answer · 2019-02-26T20:08:14

This the expected execution behavior for the version of the template you are using (2017-02-28).

You can switch your request mapping template version to 2018-05-29 and your response mapping template will be executed, with the following characteristics:

If the datasource invocation result is null, the response mapping template is executed.
If the datasource invocation yields an error, it is now up to you to handle the error. The invocation error is accessible using $ctx.error.
The response mapping template evaluated result will always be placed inside the GraphQL response data block. You can also raise or append an error using $util.error() and $util.appendError() respectively.

More info https://docs.aws.amazon.com/appsync/latest/devguide/resolver-mapping-template-changelog.html#aws-appsync-resolver-mapping-template-version-2018-05-29

So for your example:

{
  "version" : "2018-05-29", ## Note the new version
  "operation" : "DeleteItem",
  "key" : {
      "id": { "S" : "$ctx.args.id"},
      "sortKey" : { "S" : "$ctx.args.sortKey"}
  }
}

and response template

#if ( $ctx.error )
    $util.error($ctx.error.message, $ctx.error.type)
#end
#set($ctx.result.status = "SUCCESS")
#set($ctx.result.message = "This was a success!")
$utils.toJson($ctx.result)

AWS AppSync - DeleteItem doesn't execute response mapping template

1 Answers