Ability to remove BelongsTo relationship

projects/angular2-jsonapi/src/services/json-api-datastore.service.spec.ts

@@ -3,7 +3,7 @@ import { parseISO } from 'date-fns';
 import { Author } from '../../test/models/author.model';
 import { Chapter } from '../../test/models/chapter.model';
 import { AUTHOR_API_VERSION, AUTHOR_MODEL_ENDPOINT_URL, CustomAuthor } from '../../test/models/custom-author.model';
-import { AUTHOR_BIRTH, AUTHOR_ID, AUTHOR_NAME, BOOK_TITLE, getAuthorData } from '../../test/fixtures/author.fixture';
+import { AUTHOR_BIRTH, AUTHOR_ID, AUTHOR_NAME, BOOK_TITLE, getAuthorData, getIncludedBooks } from '../../test/fixtures/author.fixture';
 import { HttpClientTestingModule, HttpTestingController } from '@angular/common/http/testing';
 import { API_VERSION, BASE_URL, Datastore } from '../../test/datastore.service';
 import { ErrorResponse } from '../models/error-response.model';
@@ -695,5 +695,32 @@ describe('JsonApiDatastore', () => {
       saveRequest.flush({});
 
     });
+
+    it('should remove empty BelongsTo-relationship', () => {
+      const BOOK_NUMBER = 2;
+      const DATA = getAuthorData('books', BOOK_NUMBER);
+      const author = new Author(datastore, DATA);
+      author.syncRelationships(DATA, getIncludedBooks(BOOK_NUMBER, 'books.category'));
+
+      expect(author.books).toBeDefined();
+      expect(author.books.length).toBe(BOOK_NUMBER);
+
+      const firstBook = author.books[0];
+      expect(firstBook.category).toBeDefined();
+      expect(firstBook.category.name).toBeDefined();
+
+      const expectedUrl = `${BASE_URL}/${API_VERSION}/books/${firstBook.id}`;
+
+      firstBook.category = null;
+      firstBook.save().subscribe();
+
+      const saveRequest = httpMock.expectOne({method: 'PATCH', url: expectedUrl});
+      const obj = saveRequest.request.body.data;
+      expect(obj.relationships).toBeDefined();
+      expect(obj.relationships.category).toBeDefined();
+      expect(obj.relationships.category.data).toBeNull();
+
+      saveRequest.flush({});
+    });
   });
 });

projects/angular2-jsonapi/src/services/json-api-datastore.service.ts

@@ -1,16 +1,18 @@
 import { Injectable } from '@angular/core';
 import { HttpClient, HttpErrorResponse, HttpHeaders, HttpResponse } from '@angular/common/http';
-import { find } from 'lodash-es';
-import { catchError, map } from 'rxjs/operators';
 import { Observable, of, throwError } from 'rxjs';
+import { catchError, map } from 'rxjs/operators';
+
+import { find } from 'lodash-es';
+import * as qs from 'qs';
+import 'reflect-metadata';
+
 import { JsonApiModel } from '../models/json-api.model';
 import { ErrorResponse } from '../models/error-response.model';
 import { JsonApiQueryData } from '../models/json-api-query-data';
-import * as qs from 'qs';
 import { DatastoreConfig } from '../interfaces/datastore-config.interface';
 import { ModelConfig } from '../interfaces/model-config.interface';
 import { AttributeMetadata } from '../constants/symbols';
-import 'reflect-metadata';
 
 export type ModelType<T extends JsonApiModel> = new(datastore: JsonApiDatastore, data: any) => T;
 
@@ -287,6 +289,15 @@ export class JsonApiDatastore {
               data: relationshipData
             };
           }
+        } else if (data[key] === null) {
+          const entity = belongsToMetadata.find((it: any) => it.propertyName === key);
+          if (entity) {
+            relationships = relationships || {};
+            const relationshipKey = entity.relationship;
+            relationships[relationshipKey] = {
+              data: null
+            };
+          }
         }
       }
     }
@@ -461,6 +472,10 @@ export class JsonApiDatastore {
     for (const relationship in relationships) {
       if (relationships.hasOwnProperty(relationship) && model.hasOwnProperty(relationship)) {
         const relationshipModel: JsonApiModel = model[relationship];
+        if (relationshipModel === null) {
+          continue;
+        }
+
         const hasMany: any[] = Reflect.getMetadata('HasMany', relationshipModel);
         const propertyHasMany: any = find(hasMany, (property) => {
           return modelsTypes[property.relationship] === model.constructor;