Delegate Directive not being assigned correctly with ITypeRewriter

[kyrim]

Describe the bug
We have a use case where we have an API Gateway that will be stitching multiple microservices into one schema. As part of this, we would like to automatically remove certain field arguments (based on a naming convention, in the future potentially a marker directive) from the microservice schema and automatically inject these fields using ContextData from the API Gateway eg:

public class ContextDataMiddleware
{
	private const string ContextUserIdFieldName = "userId";

	// The fields we want to replace with ContextData and not expose
	public static readonly string[] ContextFieldNames = { ContextUserIdFieldName };
	
	public static FieldMiddleware Middleware => next => async context =>
	{
		context.ContextData[ContextUserIdFieldName] = 5;

		await next.Invoke(context);
	};
}

Then rewrite any field with that argument ("userId") with a delegation directive and remove the field from the exposed API eg.

public class ContextDataArgumentRewriter : ITypeRewriter
{
	private readonly string _schema;
	private readonly HashSet<string> _contextDataFields;

	public ContextDataArgumentRewriter(string schema, params string[] contextDataFields)
	{
		_schema = schema;
		_contextDataFields = new HashSet<string>(contextDataFields);
	}

	public ITypeDefinitionNode Rewrite(ISchemaInfo schema, ITypeDefinitionNode typeDefinition)
	{
		if (!(typeDefinition is ObjectTypeDefinitionNode objectTypeDefinition)) return typeDefinition;
	
		var fields = new List<FieldDefinitionNode>();
		
		foreach (var field in objectTypeDefinition.Fields)
		{
			var contextDataArguments = field.Arguments.Where(x => _contextDataFields.Contains(x.Name.Value)).ToList();
			if (!contextDataArguments.Any())
			{
				fields.Add(field);
				continue;
			}

			var normalArguments = field.Arguments.Except(contextDataArguments).ToList();

			var normalArgumentNodes = 
				normalArguments.Select(
					x => new ArgumentNode(x.Name, new ScopedVariableNode(
						null,
						new NameNode(ScopeNames.Arguments),
						x.Name)));
			
			var contextDataArgumentNodes = 
				contextDataArguments.Select(
					x => new ArgumentNode(x.Name, new ScopedVariableNode(
						null,
						new NameNode(ScopeNames.ContextData),
						x.Name)));

			var path = new SelectionPathComponent(
				field.Name, 
				normalArgumentNodes.Concat(contextDataArgumentNodes).ToList()
			);

			fields.Add(
				field
					// Doesn't seem to add the delegate directive in the resultant schema
					.AddDelegationPath(_schema, path)
					// Ensure we exclude these fields we are now filling
					.WithArguments(normalArguments)
			);
		}
		
		return objectTypeDefinition.WithFields(fields);
	}
}

Even after using the new AddDelegationPath method:

...
field.AddDelegationPath(_schema, path)
...

The resultant schema does not seem to have the field with the directive applied, and does not show in GraphQL Playground / Graphiql (may be a seperate issue?):

Running a query where we expect the field to be filled with ContextData and sent to the microservice does not seem to work.

To Reproduce
Please see example project: schema-stitch-test (1).zip

Run both the ApiGateway and Microservice projects concurrently.

Notice Microservice has a "userId" argument, and ApiGateway does not, for the "userFeed" field.

Run a query like:

{
  userFeed(limit: 5) {
    cursor
  }
}

Notice you will receive an error: ""The argument userId is required and does not allow null values." and the resultant schema does show the delegate on the field argument.

Expected behavior
The Delegate directive should be applied and queries where the delegate is used should automatically fill with the context data when sent to the stitched service.

Desktop (please complete the following information):

• OS: Windows 10, MacOS
• Version: v9.0.0-preview.36

Additional context
As discussed on slack here.

[kyrim]

As a side note, I don't think custom directives are outputted on fields/arguments via introspection as per:
graphql/graphql-spec#300, that might be why Playground/ graphiql are not showing the delegate directive there.

[michaelstaib]

As a side note, I don't think custom directives are outputted on fields/arguments via introspection as per: ...

They are not. But you are able to export the HC schema as SDL and then import that into the stitching layer. Just if you want to go that route.

Also, with V10 we will provide a schema registry that will have those information.

[michaelstaib]

We got this working now... the default rules where overwriting the custom type rewriters.

[kyrim]

Just tested, works perfectly! :)