Use GraphQL for epic date updates

Use GraphQL mutation `updateEpic` to update
epic startDate and dueDate.

ee/app/assets/javascripts/epic/queries/updateEpic.mutation.graphql

+mutation updateEpic($updateEpicInput: UpdateEpicInput!) {
+  updateEpic(input: $updateEpicInput) {
+    clientMutationId
+    errors
+  }
+}

ee/app/assets/javascripts/epic/store/actions.js

@@ -7,6 +7,8 @@ import { visitUrl } from '~/lib/utils/url_utility';
 import epicUtils from '../utils/epic_utils';
 import { statusType, statusEvent, dateTypes } from '../constants';
 
+import updateEpic from '../queries/updateEpic.mutation.graphql';
+
 import * as types from './mutation_types';
 
 export const setEpicMeta = ({ commit }, meta) => commit(types.SET_EPIC_META, meta);
@@ -125,23 +127,35 @@ export const requestEpicDateSaveFailure = ({ commit }, data) => {
   );
 };
 export const saveDate = ({ state, dispatch }, { dateType, dateTypeIsFixed, newDate }) => {
-  const requestBody = {
-    [dateType === dateTypes.start ? 'start_date_is_fixed' : 'due_date_is_fixed']: dateTypeIsFixed,
+  const updateEpicInput = {
+    iid: `${state.epicId}`,
+    groupPath: state.groupPath,
+    [dateType === dateTypes.start ? 'startDateIsFixed' : 'dueDateIsFixed']: dateTypeIsFixed,
   };
 
   if (dateTypeIsFixed) {
-    requestBody[dateType === dateTypes.start ? 'start_date_fixed' : 'due_date_fixed'] = newDate;
+    updateEpicInput[dateType === dateTypes.start ? 'startDateFixed' : 'dueDateFixed'] = newDate;
   }
 
   dispatch('requestEpicDateSave', { dateType });
-  axios
-    .put(state.endpoint, requestBody)
-    .then(() => {
+  epicUtils.gqClient
+    .mutate({
+      mutation: updateEpic,
+      variables: {
+        updateEpicInput,
+      },
+    })
+    .then(({ data }) => {
+      if (!data?.updateEpic?.errors.length) {
         dispatch('requestEpicDateSaveSuccess', {
           dateType,
           dateTypeIsFixed,
           newDate,
         });
+      } else {
+        // eslint-disable-next-line @gitlab/i18n/no-non-i18n-strings
+        throw new Error('An error occurred while saving the date');
+      }
     })
     .catch(() => {
       dispatch('requestEpicDateSaveFailure', {

ee/app/assets/javascripts/epic/utils/epic_utils.js

@@ -3,11 +3,14 @@ import Cookies from 'js-cookie';
 
 import { __, s__, sprintf } from '~/locale';
 
+import createGqClient from '~/lib/graphql';
 import { parseBoolean } from '~/lib/utils/common_utils';
 import { dateInWords, parsePikadayDate } from '~/lib/utils/datetime_utility';
 
 import { dateTypes } from '../constants';
 
+const gqClient = createGqClient();
+
 const triggerDocumentEvent = (eventName, eventParam) => {
   $(document).trigger(eventName, eventParam);
 };
@@ -90,6 +93,7 @@ const getDateFromMilestonesTooltip = ({
 // be default export of dependency as per
 // https://gitlab.com/help/development/testing_guide/frontend_testing.md#stubbing-and-mocking
 const epicUtils = {
+  gqClient,
   triggerDocumentEvent,
   bindDocumentEvent,
   toggleContainerClass,

ee/spec/javascripts/epic/store/actions_spec.js

@@ -605,6 +605,14 @@ describe('Epic Store Actions', () => {
 
   describe('saveDate', () => {
     let mock;
+    const mockUpdateEpicMutationRes = {
+      updateEpic: {
+        clientMutationId: null,
+        errors: [],
+        __typename: 'UpdateEpicPayload',
+      },
+    };
+
     const data = {
       dateType: dateTypes.start,
       dateTypeIsFixed: true,
@@ -621,6 +629,11 @@ describe('Epic Store Actions', () => {
 
     it('dispatches requestEpicDateSave and requestEpicDateSaveSuccess when request is successful', done => {
       mock.onPut(/(.*)/).replyOnce(200, {});
+      spyOn(epicUtils.gqClient, 'mutate').and.returnValue(
+        Promise.resolve({
+          data: mockUpdateEpicMutationRes,
+        }),
+      );
 
       testAction(
         actions.saveDate,
@@ -643,6 +656,16 @@ describe('Epic Store Actions', () => {
 
     it('dispatches requestEpicDateSave and requestEpicDateSaveFailure when request fails', done => {
       mock.onPut(/(.*)/).replyOnce(500, {});
+      spyOn(epicUtils.gqClient, 'mutate').and.returnValue(
+        Promise.resolve({
+          data: {
+            updateEpic: {
+              ...mockUpdateEpicMutationRes,
+              errors: [{ foo: 'bar' }],
+            },
+          },
+        }),
+      );
 
       testAction(
         actions.saveDate,
@@ -662,54 +685,6 @@ describe('Epic Store Actions', () => {
         done,
       );
     });
-
-    it('calls `axios.put` with request body containing start date related payload when called with `dateType` as `start`', () => {
-      spyOn(axios, 'put').and.callFake(() => new Promise(() => {}));
-
-      actions.saveDate(
-        {
-          state: { endpoint: '/foo/bar' },
-          dispatch: () => {},
-        },
-        {
-          dateType: dateTypes.start,
-          newDate: '2018-1-1',
-          dateTypeIsFixed: true,
-        },
-      );
-
-      expect(axios.put).toHaveBeenCalledWith(
-        '/foo/bar',
-        jasmine.objectContaining({
-          start_date_is_fixed: true,
-          start_date_fixed: '2018-1-1',
-        }),
-      );
-    });
-
-    it('calls `axios.put` with request body containing due date related payload when called with `dateType` as `due`', () => {
-      spyOn(axios, 'put').and.callFake(() => new Promise(() => {}));
-
-      actions.saveDate(
-        {
-          state: { endpoint: '/foo/bar' },
-          dispatch: () => {},
-        },
-        {
-          dateType: dateTypes.due,
-          newDate: '2018-1-1',
-          dateTypeIsFixed: true,
-        },
-      );
-
-      expect(axios.put).toHaveBeenCalledWith(
-        '/foo/bar',
-        jasmine.objectContaining({
-          due_date_is_fixed: true,
-          due_date_fixed: '2018-1-1',
-        }),
-      );
-    });
   });
 
   describe('requestEpicSubscriptionToggle', () => {