When using schema stitching, how the @merge/@key directive should look like for an endpoint that receives 2 or more arguments?

[alexandra-c]

Hello,
I'm having troubles with @merge directive while trying to stitch an endpoint that receives 2 arguments. I can't figure out how the @merge directive or @key directive should look like.

This is my schema:

type MasterPartner @key(selectionSet: "{ uniqueId partnerTypeId }") {
  id: Int!
  partnerTypeId: Int
  uniqueId: String
  partnerName: String
  firstName: String
  lastName: String
  email: String
  phoneNumber: String
  countyId: Int
  countyName: String
  cityId: Int
  cityName: String
  street: String
  streetNumber: String
  buildingNumber: String
  stairNumber: String
  floorNumber: String
  flatNumber: String
}

extend type Query {
  masterPartner(uniqueId: String!, partnerTypeId: Int!): MasterPartner! @merge(keyArg: "uniqueId,partnerTypeId")
}

So my masterPartner endpoint takes 2 arguments, the @merge directive says i have to use the keyArg property when having more that one arguments, but i do not understand how the value received by keyArg should look like.

As a workaround, i did this:

input PartnerInput {
  uniqueId: String!
  partnerTypeId: Int!
}

extend type Query {
  masterPartner(input: PartnerInput!): MasterPartner @merge
}

It works as expected but i don't want to apply this restriction to all my endpoints and only allow them to have 1 argument. I need to allow endpoints to receive multiple input arguments.

I red all the Directives SDL documentation but couldn't wrap my head around it and make this work...
What am i doing wrong?

Thank you!

[yaacovCR]

You are doing nothing wrong at all!

The current basic arguments to the @merge directive let you pick an argument for your root field to which you would like to forward your key, and also let you customize your key.

The keyArg argument to @merge selects the argument on the root field while either:
(A) The keyField argument to @merge selects a single field from the key (in which case the @key directive is not necessary),
(B) The key argument to @merge lets you build a custom key just for that argument from the selectionSet included by the @key directive,
(C) specifying neither will pass the entire selectionSet included by the @key directive to that argument.

Leaving out keyArg means that your resolver has to have just one argument.

The thought is that in most cases, the additional arguments will be static, which can be customized via the additionalArgs argument to @merge.

Of course, most is not at all. We decided not to complicate what's already complicated by supporting more complex syntax to keyArg and keyField/key that would support multiple arguments. In the future, I suppose we can have an argument keyInstructions (?) that accepts a list of input object of type keyArg and keyField/key.

For now, we have the following additional not so documented arguments: argsExpr, which you would use like so:

type MasterPartner @key(selectionSet: "{ uniqueId partnerTypeId }") {
  id: Int!
  partnerTypeId: Int
  uniqueId: String
  ...
}

extend type Query {
  masterPartner(
    uniqueId: String!,
    partnerTypeId: Int!
  ): MasterPartner! @merge(argsExpr: "uniqueId: $key.uniqueId, partnerTypeId: $key.partnerTypeId")
}

See:
https://github.com/ardatan/graphql-tools/blob/master/packages/stitching-directives/tests/stitchingDirectivesTransformer.test.ts#L207-L216

We are open to pull requests if you want to work on multiple keyArg and keyField/key combinations as above....

[alexandra-c]

I tried exactly like this

type MasterPartner @key(selectionSet: "{ uniqueId partnerTypeId }") {
id: Int!
partnerTypeId: Int
uniqueId: String
...
}

extend type Query {
masterPartner(
uniqueId: String!,
partnerTypeId: Int!
): MasterPartner! @merge(argsExpr: "uniqueId: $key.uniqueId, partnerTypeId: $key.partnerTypeId")
}

but i get the following error: Cannot use @merge directive without 'keyArg' argument if resolver takes more than one argument.

[yaacovCR]

Ah. We should disable that check when using argsExpr

[alexandra-c]

Should i post a new issue?
To disable that check i guess is enough just to skip the following line if the 'mergeArgsExpr' is not null, right?

graphql-tools/packages/stitching-directives/src/stitchingDirectivesValidator.ts

Lines 78 to 82 in dfd9005

	if (args.length !== 1) {
	throw new Error(
	'Cannot use @merge directive without `keyArg` argument if resolver takes more than one argument.'
	);
	}

I can create a PR with this small fix if that's ok...

[yaacovCR]

That would be great, thanks!!!!

[alexandra-c]

here's the PR #2834 😊