fix(fetch-sections,fetch-topics): Prevent error because of missing se…

…ctions or topics

src/fetchSections/index.js

@@ -10,6 +10,12 @@ const fetchSection = require('../fetchSection');
  **/
 function fetchSections(sections, { _fetchSection }) {
 	return new Promise(pResolve => {
+		// in case of there are sections
+		if (Object.keys(sections).length <= 0) {
+			pResolve({});
+			return;
+		}
+
 		pSeries(
 			Object.keys(sections).map((sectionKey, sectionIndex) =>
 				_fetchSection.bind(null, { sections, sectionKey, sectionIndex })

src/fetchSections/index.spec.js

@@ -17,4 +17,17 @@ describe('fetchSections', () => {
 			done();
 		});
 	});
+	it('fetch without sections', done => {
+		const _fetchSections = resolve(fetchSections, {
+			fetchSection: () => {
+				return new Promise(pResolve => {
+					pResolve({});
+				});
+			},
+		});
+		_fetchSections({}).then(results => {
+			expect(results).toEqual({});
+			done();
+		});
+	});
 });

src/fetchTopics/index.js

@@ -10,6 +10,12 @@ const fetchTopic = require('../fetchTopic');
  **/
 function fetchTopics({ sections, sectionKey, sectionIndex }, { _fetchTopic }) {
 	return new Promise(pResolve => {
+		// in case of there are no topics in this section
+		if (Object.keys(sections[sectionKey].topics).length <= 0) {
+			pResolve({});
+			return;
+		}
+
 		pSeries(
 			Object.keys(sections[sectionKey].topics).map((topicKey, topicIndex) =>
 				_fetchTopic.bind(null, { sections, sectionKey, sectionIndex }, { topicKey, topicIndex })

src/fetchTopics/index.spec.js

@@ -26,4 +26,26 @@ describe('fetchTopics', () => {
 			done();
 		});
 	});
+	it('fetch without topics', done => {
+		const _fetchTopics = resolve(fetchTopics, {
+			fetchTopic() {
+				return new Promise(pResolve => {
+					pResolve({ a: {} });
+				});
+			},
+		});
+		const props = {
+			sections: {
+				section1: {
+					topics: {},
+				},
+			},
+			sectionKey: 'section1',
+			sectionIndex: 0,
+		};
+		_fetchTopics(props).then(results => {
+			expect(results).toEqual({});
+			done();
+		});
+	});
 });