fix: resolveType in interfaces requires a type as string from graphql 16.1

Author: nodkz

src/discriminators/DiscriminatorTypeComposer.ts

@@ -7,6 +7,7 @@ import {
   ObjectTypeComposerFieldConfigDefinition,
   ObjectTypeComposerFieldConfigMapDefinition,
   ObjectTypeComposerFieldConfigAsObjectDefinition,
+  graphqlVersion,
 } from 'graphql-compose';
 import type { Model } from 'mongoose';
 import { composeWithMongoose, ComposeWithMongooseOpts } from '../composeWithMongoose';
@@ -144,11 +145,21 @@ export class DiscriminatorTypeComposer<TSource, TContext> extends ObjectTypeComp
         const childDName = value[baseTC.getDKey()];
 
         if (childDName) {
-          return baseTC.schemaComposer.getOTC(childDName).getType();
+          if (graphqlVersion >= 16) {
+            // in GraphQL v16 we must return TypeName
+            return childDName;
+          } else {
+            // in GraphQL below v16 we must return ObjectType
+            return baseTC.schemaComposer.getOTC(childDName).getType();
+          }
         }
 
         // as fallback return BaseModelTC
-        return baseTC.schemaComposer.getOTC(baseTC.getTypeName()).getType();
+        if (graphqlVersion >= 16) {
+          return baseTC.getTypeName();
+        } else {
+          return baseTC.schemaComposer.getOTC(baseTC.getTypeName()).getType();
+        }
       },
       fields: interfaceFields as any,
     });

src/errors/index.ts

@@ -1,4 +1,4 @@
-import type { InterfaceTypeComposer, SchemaComposer } from 'graphql-compose';
+import { graphqlVersion, InterfaceTypeComposer, SchemaComposer } from 'graphql-compose';
 import { getMongoErrorOTC } from './MongoError';
 import { ValidationError, getValidationErrorOTC } from './ValidationError';
 import { RuntimeError, getRuntimeErrorOTC } from './RuntimeError';
@@ -26,9 +26,18 @@ export function getErrorInterface(schemaComposer: SchemaComposer<any>): Interfac
     schemaComposer.addSchemaMustHaveType(MongoErrorOTC);
     schemaComposer.addSchemaMustHaveType(RuntimeErrorOTC);
 
-    const ValidationErrorType = ValidationErrorOTC.getType();
-    const MongoErrorType = MongoErrorOTC.getType();
-    const RuntimeErrorType = RuntimeErrorOTC.getType();
+    let ValidationErrorType: any;
+    let MongoErrorType: any;
+    let RuntimeErrorType: any;
+    if (graphqlVersion >= 16) {
+      ValidationErrorType = ValidationErrorOTC.getTypeName();
+      MongoErrorType = MongoErrorOTC.getTypeName();
+      RuntimeErrorType = RuntimeErrorOTC.getTypeName();
+    } else {
+      ValidationErrorType = ValidationErrorOTC.getType();
+      MongoErrorType = MongoErrorOTC.getType();
+      RuntimeErrorType = RuntimeErrorOTC.getType();
+    }
 
     iftc.setResolveType((value) => {
       switch (value?.name) {