Iterate Over Custom Directives in GraphQL Schema - graphql

Question

I have a simplified schema.graphql file with one type and one custom directive (at the field and object level). In Typescript, how can I programmatically get the type and type directive, and iterate over the fields and field directives?
type Test #myCustomDirective() {
id: String! #myCustomDirective()
}
This post says "This is not currently supported by GraphQL":
Is there any way to read GraphQL Directives on a Type with Query Introspection?
And the GitHub issue says this feature is being considered:
https://github.com/graphql/graphql-spec/issues/300
Then how is AWS AppSync doing this? See below.
// The following keeps custom directives:
parse(schema); // Return type: graphql.DocumentNode
// The following removes custom directives:
buildSchema(schema); // Return type: GraphQLSchema
AWS AppSync > Export Schema > Schema.json does include custom directives but is an AWS AppSync specific solution and is an expensive API operation.
aws appsync get-introspection-schema --api-id abc123 --format JSON --include-directives output.json
I tried GraphQL Code Generator Introspection plugin. But it removes custom directives from types and fields.
https://www.graphql-code-generator.com/plugins/introspection
I tried graphql/utilities but it also removes custom directives from types and fields.
graphql.introspectionFromSchema(graphqlSchema)
// or
graphql.graphqlSync({ schema: graphqlSchema, source: graphql.getIntrospectionQuery() }).data as unknown as graphql.IntrospectionQuery;
https://graphql.org/graphql-js/utilities/

Answer 1

This "GraphQL Tools" approach creates an iteratable schema but may not be the most efficient approach:
"The graphql-tools package allows you to create a GraphQL.js GraphQLSchema instance from GraphQL schema language using the function makeExecutableSchema"
https://www.graphql-tools.com/docs/generate-schema
import { promises as fs } from 'fs';
import { makeExecutableSchema } from '#graphql-tools/schema';
import gql from 'graphql-tag';
const schemaFile = await fs.readFile(
'./schema.graphql'
);
const executableSchema = makeExecutableSchema({
typeDefs: gql(schemaFile.toString())
});``
const output = executableSchema.getType('Test');
// output.astNode.directives sample output:
{
kind: 'Directive',
name: { kind: 'Name', value: 'myCustomDirective1' },
arguments: [ [Object] ]
},
{
kind: 'Directive',
name: { kind: 'Name', value: 'myCustomDirective' },
arguments: [ [Object] ]
}
// output.astNode['fields'] sample output:
[{
kind: 'FieldDefinition',
description: undefined,
name: { kind: 'Name', value: 'id' },
arguments: [],
type: { kind: 'NamedType', name: [Object] },
directives: [ [Object] ]
}]