fix(discriminator): Copy relations to child type composers

Author: danez

src/discriminators/__tests__/composeChildTC-test.ts

@@ -8,6 +8,15 @@ beforeAll(() => schemaComposer.clear());
 
 describe('composeChildTC ->', () => {
   const CharacterDTC = composeWithMongooseDiscriminators(CharacterModel);
+  CharacterDTC.addRelation('friends', {
+    resolver: () => CharacterDTC.getResolver('findById'),
+    prepareArgs: {
+      _id: (source) => source.friends,
+    },
+    projection: { friends: 1 },
+  });
+  CharacterDTC.extendField('friends', { type: '[String!]' });
+
   const PersonTC = CharacterDTC.discriminator(PersonModel);
   const DroidTC = CharacterDTC.discriminator(DroidModel);
 
@@ -21,6 +30,16 @@ describe('composeChildTC ->', () => {
     expect(PersonTC.getFieldNames()).toEqual(expect.arrayContaining(CharacterDTC.getFieldNames()));
   });
 
+  it('should copy all relations from BaseDTC to ChildTCs', () => {
+    expect(DroidTC.getRelations()).toEqual(CharacterDTC.getRelations());
+    expect(PersonTC.getRelations()).toEqual(CharacterDTC.getRelations());
+  });
+
+  it('should copy the extended Field from BaseDTC to ChildTCs', () => {
+    expect(DroidTC.getField('friends').type).toEqual(CharacterDTC.getField('friends').type);
+    expect(PersonTC.getField('friends').type).toEqual(CharacterDTC.getField('friends').type);
+  });
+
   it('should make childTC have same fieldTypes as baseTC', () => {
     const characterFields = CharacterDTC.getFieldNames();
 

src/discriminators/composeChildTC.ts

@@ -6,6 +6,22 @@ import type {
 import { prepareChildResolvers } from './prepareChildResolvers';
 import { reorderFields } from './utils/reorderFields';
 
+function copyBaseTcRelationsToChildTc(
+  baseDTC: ObjectTypeComposer<any, any>,
+  childTC: ObjectTypeComposer<any, any>
+) {
+  const relations = baseDTC.getRelations();
+  const childRelations = childTC.getRelations();
+  Object.keys(relations).forEach((name) => {
+    if (childRelations[name]) {
+      return;
+    }
+    childTC.addRelation(name, relations[name] as any);
+  });
+
+  return childTC;
+}
+
 // copy all baseTypeComposer fields to childTC
 // these are the fields before calling discriminator
 function copyBaseTCFieldsToChildTC(
@@ -35,7 +51,8 @@ export function composeChildTC<TSource, TContext>(
   childTC: ObjectTypeComposer<TSource, TContext>,
   opts: ComposeWithMongooseDiscriminatorsOpts<TContext>
 ): ObjectTypeComposer<TSource, TContext> {
-  const composedChildTC = copyBaseTCFieldsToChildTC(baseDTC, childTC);
+  let composedChildTC = copyBaseTcRelationsToChildTc(baseDTC, childTC);
+  composedChildTC = copyBaseTCFieldsToChildTC(baseDTC, composedChildTC);
 
   composedChildTC.addInterface(baseDTC.getDInterface());