feat: allow removing a pointer from a field

CHANGELOG.md

@@ -103,7 +103,7 @@ ___
 ## Breaking Changes
   - (none)
 ## Features
-  - (none)
+  - Allow a pointer to be removed using GraphQL (Chris Bland) [#7517](https://github.com/parse-community/parse-server/issues/7517)
 ## Bug Fixes
   - (none)
 

spec/ParseGraphQLServer.spec.js

@@ -8324,6 +8324,73 @@ describe('ParseGraphQLServer', () => {
           expect(result.company.name).toEqual('imACompany2');
         });
 
+        it('should support removing pointer on update', async () => {
+          const company = new Parse.Object('Company');
+          company.set('name', 'imACompany1');
+          await company.save();
+
+          const country = new Parse.Object('Country');
+          country.set('name', 'imACountry');
+          country.set('company', company);
+          await country.save();
+
+          await parseGraphQLServer.parseGraphQLSchema.schemaCache.clear();
+
+          const {
+            data: {
+              updateCountry: { country: result },
+            },
+          } = await apolloClient.mutate({
+            mutation: gql`
+              mutation Update($id: ID!, $fields: UpdateCountryFieldsInput) {
+                updateCountry(input: { id: $id, fields: $fields }) {
+                  country {
+                    id
+                    objectId
+                    company {
+                      id
+                      objectId
+                      name
+                    }
+                  }
+                }
+              }
+            `,
+            variables: {
+              id: country.id,
+              fields: {
+                company: { unlink: true },
+              },
+            },
+          });
+
+          expect(result.id).toBeDefined();
+          expect(result.company).toBeNull();
+
+          const {
+            data: { country: result1 },
+          } = await apolloClient.query({
+            query: gql`
+              query getCountry($id: ID!) {
+                country(id: $id) {
+                  id
+                  objectId
+                  company {
+                    id
+                    objectId
+                    name
+                  }
+                }
+              }
+            `,
+            variables: {
+              id: country.id,
+            },
+          });
+
+          expect(result1.countries).toBeNull();
+        });
+
         it_only_db('mongo')('should support relation and nested relation on create', async () => {
           const company = new Parse.Object('Company');
           company.set('name', 'imACompany1');

src/GraphQL/loaders/parseClassTypes.js

@@ -199,6 +199,10 @@ const load = (parseGraphQLSchema, parseClass, parseClassConfig: ?ParseGraphQLCla
           description: `Link an existing object from ${graphQLClassName} class. You can use either the global or the object id.`,
           type: GraphQLID,
         },
+        unlink: {
+          description: `Unlink an existing object from ${graphQLClassName} class.`,
+          type: GraphQLBoolean,
+        },
       };
       if (isCreateEnabled) {
         fields['createAndLink'] = {

src/GraphQL/transformers/mutation.js

@@ -224,6 +224,9 @@ const transformers = {
         objectId,
       };
     }
+    if (value.unlink) {
+      return { __op: 'Delete' };
+    }
   },
 };