Dgraph seems to refuse returning an error type when using try-catch in lambda

Users Dgraph Cloud
,
1

I’m currently trying to implement error handling with Dgraph lambdas. It has been working if I manually check for errors on the return type of eg. a query within the lambda function. However, if I wrap the entire lambda logic inside a try-catch block, and try to return the error from catch, the return object remains an empty object.

To clarify

Assume a lambda like this:

const someFunc = async ({parent, args, graphql}) => {
  try {
    // do some graphql query
    const getNode = await graphql(query, vars);

   if (getNode.errors) {
     throw new CustomError(getNode.errors[0].message);
   }

  return {
    __typename: "CustomResult"
   success: "You did it!"
  }
  } catch (error) {
    return {
     __typename: "CustomError"
    error: error.message
   }
 }
}

self.addGraphQLResolvers({
  "Query.someFunc": someFunc,
});

For a query:

query SomeFunc {
  someFunc {
    ...on CustomError {
      error 
    }
   ...on CustomResult  {
     success
   }
  }
}

The query result on error would then look like:

{
  "data": {
    "someFunc": {}
  },
  "extensions": {
    "tracing": {
      "version": 1,
      "startTime": "2022-07-01T10:04:53.538202875Z",
      "endTime": "2022-07-01T10:04:54.133881073Z",
      "duration": 595678278
    }
  }
}

However, if I remove the try-catch and test directly

const someFunc = async ({parent, args, graphql}) => {
    // do some graphql query
    const getNode = await graphql(query, vars);

   if (getNode.errors) {
     return {
       __typename: "CustomError",
       error: getNode.errors[0].message
     }
   }

  return {
    __typename: "CustomResult"
   success: "You did it!"
  }
}

self.addGraphQLResolvers({
  "Query.someFunc": someFunc,
});

it works as expected and I get the on CustomError result.

Any ideas why this is not working?