feat(): override the resolve type of interfaces

lib/federation/graphql-federation.factory.ts

@@ -1,12 +1,14 @@
 import { Injectable } from '@nestjs/common';
 import { loadPackage } from '@nestjs/common/utils/load-package.util';
-import { transformSchema } from 'apollo-graphql';
 import { isString } from '@nestjs/common/utils/shared.utils';
+import { transformSchema } from 'apollo-graphql';
 import { gql } from 'apollo-server-core';
 import {
   GraphQLAbstractType,
   GraphQLField,
+  GraphQLInputField,
   GraphQLInputObjectType,
+  GraphQLInterfaceType,
   GraphQLObjectType,
   GraphQLResolveInfo,
   GraphQLSchema,
@@ -18,8 +20,6 @@ import {
   isUnionType,
 } from 'graphql';
 import { mergeSchemas } from 'graphql-tools';
-import { PromiseOrValue } from 'graphql/jsutils/PromiseOrValue';
-import Maybe from 'graphql/tsutils/Maybe';
 import { forEach, isEmpty } from 'lodash';
 import { GraphQLSchemaBuilder } from '../graphql-schema.builder';
 import { GqlModuleOptions } from '../interfaces';
@@ -137,13 +137,10 @@ export class GraphQLFederationFactory {
   ): GraphQLSchema {
     return transformSchema(executableSchema, (type) => {
       if (isUnionType(type) && type.name !== '_Entity') {
-        return this.overrideFederatedUnionResolveType(
-          type,
-          autoGeneratedSchema,
-        );
-      } else if (isEnumType(type)) {
-        return autoGeneratedSchema.getType(type.name);
+        return this.overrideFederatedResolveType(type, autoGeneratedSchema);
       } else if (isInterfaceType(type)) {
+        return this.overrideFederatedResolveType(type, autoGeneratedSchema);
+      } else if (isEnumType(type)) {
         return autoGeneratedSchema.getType(type.name);
       } else if (isInputObjectType(type)) {
         const autoGeneratedInputType = autoGeneratedSchema.getType(
@@ -154,16 +151,14 @@ export class GraphQLFederationFactory {
           return type;
         }
         const fields = type.getFields();
-        forEach(
-          fields,
-          (value: GraphQLField<unknown, unknown>, key: string) => {
-            const field = autoGeneratedInputType.getFields()[key];
-            if (!field) {
-              return;
-            }
-            value.extensions = field.extensions;
-          },
-        );
+        forEach(fields, (value: GraphQLInputField, key: string) => {
+          const field = autoGeneratedInputType.getFields()[key];
+          if (!field) {
+            return;
+          }
+          value.extensions = field.extensions;
+          value.astNode = field.astNode;
+        });
         type.extensions = autoGeneratedInputType.extensions;
         return type;
       } else if (isObjectType(type)) {
@@ -198,39 +193,39 @@ export class GraphQLFederationFactory {
   }
 
   /**
-   * Ensures that the resolveType method for unions in the federated schema
+   * Ensures that the resolveType method for unions and interfaces in the federated schema
    * is properly set from the one in the autoGeneratedSchema.
    */
-  private overrideFederatedUnionResolveType(
-    unionInFederatedSchema: GraphQLUnionType,
+  private overrideFederatedResolveType(
+    typeInFederatedSchema: GraphQLUnionType | GraphQLInterfaceType,
     autoGeneratedSchema: GraphQLSchema,
-  ): GraphQLUnionType {
+  ): GraphQLUnionType | GraphQLInterfaceType {
     // Get the matching type from the auto generated schema
-    const autogeneratedUnionType = autoGeneratedSchema.getType(
-      unionInFederatedSchema.name,
+    const autoGeneratedType = autoGeneratedSchema.getType(
+      typeInFederatedSchema.name,
     );
     // Bail if inconsistent with original schema
     if (
-      !autogeneratedUnionType ||
-      !(autogeneratedUnionType instanceof GraphQLUnionType) ||
-      !autogeneratedUnionType.resolveType
+      !autoGeneratedType ||
+      !(autoGeneratedType instanceof GraphQLUnionType) ||
+      !autoGeneratedType.resolveType
     ) {
-      return unionInFederatedSchema;
+      return typeInFederatedSchema;
     }
 
-    unionInFederatedSchema.resolveType = async (
-      value: any,
-      context: any,
+    typeInFederatedSchema.resolveType = async (
+      value: unknown,
+      context: unknown,
       info: GraphQLResolveInfo,
       abstractType: GraphQLAbstractType,
     ) => {
-      const resultFromAutogenSchema = await autogeneratedUnionType.resolveType(
+      const resultFromAutogenSchema = await autoGeneratedType.resolveType(
         value,
         context,
         info,
         abstractType,
       );
-      // if the result is not a GraphQLObjectType we're fine
+      // If the result is not a GraphQLObjectType we're fine
       if (!resultFromAutogenSchema || isString(resultFromAutogenSchema)) {
         return resultFromAutogenSchema;
       }
@@ -253,7 +248,6 @@ export class GraphQLFederationFactory {
       // name of the type and hope apollo works it out
       return resultFromAutogenSchema.name;
     };
-
-    return unionInFederatedSchema;
+    return typeInFederatedSchema;
   }
 }