Extended Web IDE API to get MRs for a certain branch in a project

 New `Api.projectMergeRequests` allows:
 - to query for all MRs on a project without specifying `mergeRequestId`
 - to filter the returned MRs using parameters from
 https://bit.ly/2H7We4V

 The new API request is used for fetching information about MRs
 associated with a particular branch in Web IDE to have IdeSidebar
 behave consistently in both scenarios:
 - getting to a branch from and MR (where we already have info about
 relevant MR), or
 - getting to a branch somehow differently directly

For cases where there are several merge requests that the current branch
is associated with, mark the most recent one as 'current'

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/49663

app/assets/javascripts/api.js

@@ -12,6 +12,7 @@ const Api = {
   projectsPath: '/api/:version/projects.json',
   projectPath: '/api/:version/projects/:id',
   projectLabelsPath: '/:namespace_path/:project_path/labels',
+  projectMergeRequestsPath: '/api/:version/projects/:id/merge_requests',
   projectMergeRequestPath: '/api/:version/projects/:id/merge_requests/:mrid',
   projectMergeRequestChangesPath: '/api/:version/projects/:id/merge_requests/:mrid/changes',
   projectMergeRequestVersionsPath: '/api/:version/projects/:id/merge_requests/:mrid/versions',
@@ -111,6 +112,22 @@ const Api = {
     return axios.get(url);
   },
 
+  /**
+   * Get all Merge Requests for a project, eventually filtering based on
+   * supplied parameters
+   * @param projectPath
+   * @param params
+   * @returns {Promise}
+   */
+  projectMergeRequests(projectPath, params = {}) {
+    const url = Api.buildUrl(Api.projectMergeRequestsPath).replace(
+      ':id',
+      encodeURIComponent(projectPath),
+    );
+
+    return axios.get(url, { params });
+  },
+
   // Return Merge Request for project
   projectMergeRequest(projectPath, mergeRequestId, params = {}) {
     const url = Api.buildUrl(Api.projectMergeRequestPath)

app/assets/javascripts/ide/services/index.js

@@ -40,6 +40,9 @@ export default {
   getProjectData(namespace, project) {
     return Api.project(`${namespace}/${project}`);
   },
+  getProjectMergeRequests(projectId, params = {}) {
+    return Api.projectMergeRequests(projectId, params);
+  },
   getProjectMergeRequestData(projectId, mergeRequestId, params = {}) {
     return Api.projectMergeRequest(projectId, mergeRequestId, params);
   },

app/assets/javascripts/ide/stores/actions/merge_request.js

@@ -4,6 +4,38 @@ import service from '../../services';
 import * as types from '../mutation_types';
 import { activityBarViews } from '../../constants';
 
+export const getMergeRequestsForBranch = ({ commit }, { projectId, branchId } = {}) =>
+  service
+    .getProjectMergeRequests(`${projectId}`, {
+      source_branch: branchId,
+      order_by: 'created_at',
+      per_page: 1,
+    })
+    .then(({ data }) => {
+      if (data.length > 0) {
+        const currentMR = data[0];
+
+        commit(types.SET_MERGE_REQUEST, {
+          projectPath: projectId,
+          mergeRequestId: currentMR.iid,
+          mergeRequest: currentMR,
+        });
+
+        commit(types.SET_CURRENT_MERGE_REQUEST, `${currentMR.iid}`);
+      }
+    })
+    .catch(e => {
+      flash(
+        __(`Error fetching merge requests for ${branchId}`),
+        'alert',
+        document,
+        null,
+        false,
+        true,
+      );
+      throw e;
+    });
+
 export const getMergeRequestData = (
   { commit, dispatch, state },
   { projectId, mergeRequestId, targetProjectId = null, force = false } = {},

app/assets/javascripts/ide/stores/actions/project.js

@@ -136,7 +136,8 @@ export const openBranch = ({ dispatch, state }, { projectId, branchId, basePath
   return dispatch('getFiles', {
     projectId,
     branchId,
-  }).then(() => {
+  })
+    .then(() => {
       if (basePath) {
         const path = basePath.slice(-1) === '/' ? basePath.slice(0, -1) : basePath;
         const treeEntryKey = Object.keys(state.entries).find(
@@ -148,5 +149,11 @@ export const openBranch = ({ dispatch, state }, { projectId, branchId, basePath
           dispatch('handleTreeEntryAction', treeEntry);
         }
       }
+    })
+    .then(() => {
+      dispatch('getMergeRequestsForBranch', {
+        projectId,
+        branchId,
+      });
     });
 };

changelogs/unreleased/49663-branch-to-mr-connection.yml

+---
+title: Link to most recent MR from a branch
+merge_request: 25689
+author:
+type: added

spec/javascripts/api_spec.js

@@ -139,6 +139,40 @@ describe('Api', () => {
     });
   });
 
+  describe('projectMergeRequests', () => {
+    const projectPath = 'abc';
+    const expectedUrl = `${dummyUrlRoot}/api/${dummyApiVersion}/projects/${projectPath}/merge_requests`;
+
+    it('fetches all merge requests for a project', done => {
+      const mockData = [{ source_branch: 'foo' }, { source_branch: 'bar' }];
+      mock.onGet(expectedUrl).reply(200, mockData);
+      Api.projectMergeRequests(projectPath)
+        .then(({ data }) => {
+          expect(data.length).toEqual(2);
+          expect(data[0].source_branch).toBe('foo');
+          expect(data[1].source_branch).toBe('bar');
+        })
+        .then(done)
+        .catch(done.fail);
+    });
+
+    it('fetches merge requests filtered with passed params', done => {
+      const params = {
+        source_branch: 'bar',
+      };
+      const mockData = [{ source_branch: 'bar' }];
+      mock.onGet(expectedUrl, { params }).reply(200, mockData);
+
+      Api.projectMergeRequests(projectPath, params)
+        .then(({ data }) => {
+          expect(data.length).toEqual(1);
+          expect(data[0].source_branch).toBe('bar');
+        })
+        .then(done)
+        .catch(done.fail);
+    });
+  });
+
   describe('projectMergeRequest', () => {
     it('fetches a merge request', done => {
       const projectPath = 'abc';

spec/javascripts/ide/stores/actions/merge_request_spec.js

@@ -2,6 +2,7 @@ import MockAdapter from 'axios-mock-adapter';
 import axios from '~/lib/utils/axios_utils';
 import store from '~/ide/stores';
 import actions, {
+  getMergeRequestsForBranch,
   getMergeRequestData,
   getMergeRequestChanges,
   getMergeRequestVersions,
@@ -27,6 +28,98 @@ describe('IDE store merge request actions', () => {
     resetStore(store);
   });
 
+  describe('getMergeRequestsForBranch', () => {
+    describe('success', () => {
+      const mrData = { iid: 2, source_branch: 'bar' };
+      const mockData = [mrData];
+
+      describe('base case', () => {
+        beforeEach(() => {
+          spyOn(service, 'getProjectMergeRequests').and.callThrough();
+          mock.onGet(/api\/(.*)\/projects\/abcproject\/merge_requests/).reply(200, mockData);
+        });
+
+        it('calls getProjectMergeRequests service method', done => {
+          store
+            .dispatch('getMergeRequestsForBranch', { projectId: 'abcproject', branchId: 'bar' })
+            .then(() => {
+              expect(service.getProjectMergeRequests).toHaveBeenCalledWith('abcproject', {
+                source_branch: 'bar',
+                order_by: 'created_at',
+                per_page: 1,
+              });
+
+              done();
+            })
+            .catch(done.fail);
+        });
+
+        it('sets the "Merge Request" Object', done => {
+          store
+            .dispatch('getMergeRequestsForBranch', { projectId: 'abcproject', branchId: 'bar' })
+            .then(() => {
+              expect(Object.keys(store.state.projects.abcproject.mergeRequests).length).toEqual(1);
+              expect(Object.keys(store.state.projects.abcproject.mergeRequests)[0]).toEqual('2');
+              expect(store.state.projects.abcproject.mergeRequests[2]).toEqual(
+                jasmine.objectContaining(mrData),
+              );
+              done();
+            })
+            .catch(done.fail);
+        });
+
+        it('sets "Current Merge Request" object to the most recent MR', done => {
+          store
+            .dispatch('getMergeRequestsForBranch', { projectId: 'abcproject', branchId: 'bar' })
+            .then(() => {
+              expect(store.state.currentMergeRequestId).toEqual('2');
+              done();
+            })
+            .catch(done.fail);
+        });
+      });
+
+      describe('no merge requests for branch available case', () => {
+        beforeEach(() => {
+          spyOn(service, 'getProjectMergeRequests').and.callThrough();
+          mock.onGet(/api\/(.*)\/projects\/abcproject\/merge_requests/).reply(200, []);
+        });
+
+        it('does not fail if there are no merge requests for current branch', done => {
+          store
+            .dispatch('getMergeRequestsForBranch', { projectId: 'abcproject', branchId: 'foo' })
+            .then(() => {
+              expect(Object.keys(store.state.projects.abcproject.mergeRequests).length).toEqual(0);
+              expect(store.state.currentMergeRequestId).toEqual('');
+              done();
+            })
+            .catch(done.fail);
+        });
+      });
+    });
+
+    describe('error', () => {
+      beforeEach(() => {
+        mock.onGet(/api\/(.*)\/projects\/abcproject\/merge_requests/).networkError();
+      });
+
+      it('flashes message, if error', done => {
+        const flashSpy = spyOnDependency(actions, 'flash');
+
+        getMergeRequestsForBranch({ commit() {} }, { projectId: 'abcproject', branchId: 'bar' })
+          .then(() => {
+            fail('Expected getMergeRequestsForBranch to throw an error');
+          })
+          .catch(() => {
+            expect(flashSpy).toHaveBeenCalled();
+            expect(flashSpy.calls.argsFor(0)[0]).toEqual('Error fetching merge requests for bar');
+          })
+          .then(done)
+          .catch(done.fail);
+      });
+    });
+  });
+
   describe('getMergeRequestData', () => {
     describe('success', () => {
       beforeEach(() => {

spec/javascripts/ide/stores/actions/project_spec.js

@@ -249,6 +249,7 @@ describe('IDE store project actions', () => {
             ['setCurrentBranchId', branch.branchId],
             ['getBranchData', branch],
             ['getFiles', branch],
+            ['getMergeRequestsForBranch', branch],
           ]);
         })
         .then(done)