Add blocked popover feature for boards

Also
- Add vuex action for setting error state

app/assets/javascripts/boards/components/board_blocked_icon.vue

+<script>
+import { GlIcon, GlLink, GlPopover, GlLoadingIcon } from '@gitlab/ui';
+import { blockingIssuablesQueries, issuableTypes } from '~/boards/constants';
+import { IssueType } from '~/graphql_shared/constants';
+import { convertToGraphQLId } from '~/graphql_shared/utils';
+import { truncate } from '~/lib/utils/text_utility';
+import { __, n__, s__, sprintf } from '~/locale';
+
+export default {
+  i18n: {
+    issuableType: {
+      [issuableTypes.issue]: __('issue'),
+    },
+  },
+  graphQLIdType: {
+    [issuableTypes.issue]: IssueType,
+  },
+  referenceFormatter: {
+    [issuableTypes.issue]: (r) => r.split('/')[1],
+  },
+  defaultDisplayLimit: 3,
+  textTruncateWidth: 80,
+  components: {
+    GlIcon,
+    GlPopover,
+    GlLink,
+    GlLoadingIcon,
+  },
+  blockingIssuablesQueries,
+  props: {
+    item: {
+      type: Object,
+      required: true,
+    },
+    uniqueId: {
+      type: String,
+      required: true,
+    },
+    issuableType: {
+      type: String,
+      required: true,
+      validator(value) {
+        return [issuableTypes.issue].includes(value);
+      },
+    },
+  },
+  apollo: {
+    blockingIssuables: {
+      skip() {
+        return this.skip;
+      },
+      query() {
+        return blockingIssuablesQueries[this.issuableType].query;
+      },
+      variables() {
+        return {
+          id: convertToGraphQLId(this.$options.graphQLIdType[this.issuableType], this.item.id),
+        };
+      },
+      update(data) {
+        this.skip = true;
+
+        return data?.issuable?.blockingIssuables?.nodes || [];
+      },
+      error(error) {
+        const message = sprintf(s__('Boards|Failed to fetch blocking %{issuableType}s'), {
+          issuableType: this.issuableTypeText,
+        });
+        this.$emit('blocking-issuables-error', { error, message });
+      },
+    },
+  },
+  data() {
+    return {
+      skip: true,
+      blockingIssuables: [],
+    };
+  },
+  computed: {
+    displayedIssuables() {
+      const { defaultDisplayLimit, referenceFormatter } = this.$options;
+      return this.blockingIssuables.slice(0, defaultDisplayLimit).map((i) => {
+        return {
+          ...i,
+          title: truncate(i.title, this.$options.textTruncateWidth),
+          reference: referenceFormatter[this.issuableType](i.reference),
+        };
+      });
+    },
+    loading() {
+      return this.$apollo.queries.blockingIssuables.loading;
+    },
+    issuableTypeText() {
+      return this.$options.i18n.issuableType[this.issuableType];
+    },
+    blockedLabel() {
+      return sprintf(
+        n__(
+          'Boards|Blocked by %{blockedByCount} %{issuableType}',
+          'Boards|Blocked by %{blockedByCount} %{issuableType}s',
+          this.item.blockedByCount,
+        ),
+        {
+          blockedByCount: this.item.blockedByCount,
+          issuableType: this.issuableTypeText,
+        },
+      );
+    },
+    glIconId() {
+      return `blocked-icon-${this.uniqueId}`;
+    },
+    hasMoreIssuables() {
+      return this.item.blockedByCount > this.$options.defaultDisplayLimit;
+    },
+    displayedIssuablesCount() {
+      return this.hasMoreIssuables
+        ? this.item.blockedByCount - this.$options.defaultDisplayLimit
+        : this.item.blockedByCount;
+    },
+    moreIssuablesText() {
+      return sprintf(
+        n__(
+          'Boards|+ %{displayedIssuablesCount} more %{issuableType}',
+          'Boards|+ %{displayedIssuablesCount} more %{issuableType}s',
+          this.displayedIssuablesCount,
+        ),
+        {
+          displayedIssuablesCount: this.displayedIssuablesCount,
+          issuableType: this.issuableTypeText,
+        },
+      );
+    },
+    viewAllIssuablesText() {
+      return sprintf(s__('Boards|View all blocking %{issuableType}s'), {
+        issuableType: this.issuableTypeText,
+      });
+    },
+    loadingMessage() {
+      return sprintf(s__('Boards|Retrieving blocking %{issuableType}s'), {
+        issuableType: this.issuableTypeText,
+      });
+    },
+  },
+  methods: {
+    handleMouseEnter() {
+      this.skip = false;
+    },
+  },
+};
+</script>
+<template>
+  <div class="gl-display-inline">
+    <gl-icon
+      :id="glIconId"
+      ref="icon"
+      name="issue-block"
+      class="issue-blocked-icon gl-mr-2 gl-cursor-pointer"
+      data-testid="issue-blocked-icon"
+      @mouseenter="handleMouseEnter"
+    />
+    <gl-popover :target="glIconId" placement="top" triggers="hover">
+      <template #title
+        ><span data-testid="popover-title">{{ blockedLabel }}</span></template
+      >
+      <template v-if="loading">
+        <gl-loading-icon />
+        <p class="gl-mt-4 gl-mb-0 gl-font-small">{{ loadingMessage }}</p>
+      </template>
+      <template v-else>
+        <ul class="gl-list-style-none gl-p-0">
+          <li v-for="issuable in displayedIssuables" :key="issuable.id">
+            <gl-link :href="issuable.webUrl" class="gl-text-blue-500! gl-font-sm">{{
+              issuable.reference
+            }}</gl-link>
+            <p class="gl-mb-3 gl-display-block!" data-testid="issuable-title">
+              {{ issuable.title }}
+            </p>
+          </li>
+        </ul>
+        <div v-if="hasMoreIssuables" class="gl-mt-4">
+          <p class="gl-mb-3" data-testid="hidden-blocking-count">{{ moreIssuablesText }}</p>
+          <gl-link
+            data-testid="view-all-issues"
+            :href="`${item.webUrl}#related-issues`"
+            class="gl-text-blue-500! gl-font-sm"
+            >{{ viewAllIssuablesText }}</gl-link
+          >
+        </div>
+      </template>
+    </gl-popover>
+  </div>
+</template>

app/assets/javascripts/boards/components/board_card_inner.vue

@@ -10,6 +10,7 @@ import TooltipOnTruncate from '~/vue_shared/components/tooltip_on_truncate.vue';
 import UserAvatarLink from '../../vue_shared/components/user_avatar/user_avatar_link.vue';
 import { ListType } from '../constants';
 import eventHub from '../eventhub';
+import BoardBlockedIcon from './board_blocked_icon.vue';
 import IssueDueDate from './issue_due_date.vue';
 import IssueTimeEstimate from './issue_time_estimate.vue';
 
@@ -22,6 +23,7 @@ export default {
     IssueDueDate,
     IssueTimeEstimate,
     IssueCardWeight: () => import('ee_component/boards/components/issue_card_weight.vue'),
+    BoardBlockedIcon,
   },
   directives: {
     GlTooltip: GlTooltipDirective,
@@ -52,7 +54,7 @@ export default {
     };
   },
   computed: {
-    ...mapState(['isShowingLabels']),
+    ...mapState(['isShowingLabels', 'issuableType']),
     ...mapGetters(['isEpicBoard']),
     cappedAssignees() {
       // e.g. maxRender is 4,
@@ -114,7 +116,13 @@ export default {
     },
   },
   methods: {
-    ...mapActions(['performSearch']),
+    ...mapActions([
+      'performSearch',
+      'setError',
+      'setBlockingIssuables',
+      'unsetBlockingIssuables',
+      'toggleBlockedPopover',
+    ]),
     isIndexLessThanlimit(index) {
       return index < this.limitBeforeCounter;
     },
@@ -164,14 +172,14 @@ export default {
   <div>
     <div class="gl-display-flex" dir="auto">
       <h4 class="board-card-title gl-mb-0 gl-mt-0">
-        <gl-icon
+        <board-blocked-icon
           v-if="item.blocked"
-          v-gl-tooltip
-          name="issue-block"
-          :title="blockedLabel"
-          class="issue-blocked-icon gl-mr-2"
-          :aria-label="blockedLabel"
-          data-testid="issue-blocked-icon"
+          :item="item"
+          :unique-id="`${item.id}${list.id}`"
+          :issuable-type="issuableType"
+          @blocking-issuables-error="setError"
+          @blocking-issuables="setBlockingIssuables"
+          @hidden="unsetBlockingIssuables"
         />
         <gl-icon
           v-if="item.confidential"
@@ -181,13 +189,9 @@ export default {
           class="confidential-icon gl-mr-2"
           :aria-label="__('Confidential')"
         />
-        <a
-          :href="item.path || item.webUrl || ''"
-          :title="item.title"
-          class="js-no-trigger"
-          @mousemove.stop
-          >{{ item.title }}</a
-        >
+        <a :href="item.path || item.webUrl || ''" :title="item.title" @mousemove.stop>{{
+          item.title
+        }}</a>
       </h4>
     </div>
     <div v-if="showLabelFooter" class="board-card-labels gl-mt-2 gl-display-flex gl-flex-wrap">

app/assets/javascripts/boards/components/board_content.vue

@@ -69,7 +69,7 @@ export default {
     },
   },
   methods: {
-    ...mapActions(['moveList']),
+    ...mapActions(['moveList', 'unsetError']),
     afterFormEnters() {
       const el = this.canDragColumns ? this.$refs.list.$el : this.$refs.list;
       el.scrollTo({ left: el.scrollWidth, behavior: 'smooth' });
@@ -100,7 +100,7 @@ export default {
 
 <template>
   <div>
-    <gl-alert v-if="error" variant="danger" :dismissible="false">
+    <gl-alert v-if="error" variant="danger" :dismissible="true" @dismiss="unsetError">
       {{ error }}
     </gl-alert>
     <component

app/assets/javascripts/boards/constants.js

 import { __ } from '~/locale';
+import boardBlockingIssuesQuery from './graphql/board_blocking_issues.query.graphql';
 
 export const issuableTypes = {
   issue: 'issue',
@@ -45,3 +46,9 @@ export default {
   BoardType,
   ListType,
 };
+
+export const blockingIssuablesQueries = {
+  [issuableTypes.issue]: {
+    query: boardBlockingIssuesQuery,
+  },
+};

app/assets/javascripts/boards/graphql/board_blocking_issues.query.graphql

+query BoardBlockingIssues($id: IssueID!) {
+  issuable: issue(id: $id) {
+    __typename
+    id
+    blockingIssuables: blockedByIssues {
+      __typename
+      nodes {
+        id
+        iid
+        title
+        reference(full: true)
+        webUrl
+      }
+    }
+  }
+}

app/assets/javascripts/boards/index.js

@@ -107,6 +107,7 @@ export default () => {
       milestoneListsAvailable: parseBoolean($boardApp.dataset.milestoneListsAvailable),
       assigneeListsAvailable: parseBoolean($boardApp.dataset.assigneeListsAvailable),
       iterationListsAvailable: parseBoolean($boardApp.dataset.iterationListsAvailable),
+      issuableType: issuableTypes.issue,
     },
     store,
     apolloProvider,

app/assets/javascripts/boards/stores/actions.js

+import * as Sentry from '@sentry/browser';
 import { pick } from 'lodash';
 import createBoardListMutation from 'ee_else_ce/boards/graphql/board_list_create.mutation.graphql';
 import boardListsQuery from 'ee_else_ce/boards/graphql/board_lists.query.graphql';
@@ -608,6 +609,18 @@ export default {
     }
   },
 
+  setError: ({ commit }, { message, error, captureError = false }) => {
+    commit(types.SET_ERROR, message);
+
+    if (captureError) {
+      Sentry.captureException(error);
+    }
+  },
+
+  unsetError: ({ commit }) => {
+    commit(types.SET_ERROR, undefined);
+  },
+
   fetchBacklog: () => {
     notImplemented();
   },

app/assets/javascripts/boards/stores/mutation_types.js

@@ -49,3 +49,4 @@ export const SET_ADD_COLUMN_FORM_VISIBLE = 'SET_ADD_COLUMN_FORM_VISIBLE';
 export const ADD_LIST_TO_HIGHLIGHTED_LISTS = 'ADD_LIST_TO_HIGHLIGHTED_LISTS';
 export const REMOVE_LIST_FROM_HIGHLIGHTED_LISTS = 'REMOVE_LIST_FROM_HIGHLIGHTED_LISTS';
 export const RESET_BOARD_ITEM_SELECTION = 'RESET_BOARD_ITEM_SELECTION';
+export const SET_ERROR = 'SET_ERROR';

app/assets/javascripts/boards/stores/mutations.js

@@ -309,4 +309,8 @@ export default {
   [mutationTypes.RESET_BOARD_ITEM_SELECTION]: (state) => {
     state.selectedBoardItems = [];
   },
+
+  [mutationTypes.SET_ERROR]: (state, error) => {
+    state.error = error;
+  },
 };

app/assets/javascripts/boards/stores/state.js

@@ -34,4 +34,5 @@ export default () => ({
   },
   // TODO: remove after ce/ee split of board_content.vue
   isShowingEpicsSwimlanes: false,
+  activeBlockingIssuables: [],
 });

app/assets/javascripts/graphql_shared/constants.js

+/* eslint-disable @gitlab/require-i18n-strings */
+export const IssueType = 'Issue';

changelogs/unreleased/implement-blocking-issue-popover-for-boards.yml

+---
+title: Add blocked issues detail popover for boards cards
+merge_request: 55821
+author:
+type: added

doc/user/project/issue_board.md

@@ -280,6 +280,7 @@ group-level objects are available.
 #### GraphQL-based sidebar for group issue boards **(PREMIUM)**
 
 <!-- When the feature flag is removed, integrate this section into the above ("Group issue boards"). -->
+<!-- This anchor is linked from #blocked-issues as well. -->
 
 > - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/285074) in GitLab 13.9.
 > - It's [deployed behind a feature flag](../feature_flags.md), disabled by default.
@@ -407,12 +408,18 @@ To set a WIP limit for a list:
 
 ## Blocked issues
 
-> [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/34723) in GitLab 12.8.
+> - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/34723) in GitLab 12.8.
+> - [View blocking issues when hovering over blocked icon](https://gitlab.com/gitlab-org/gitlab/-/issues/210452) in GitLab 13.10.
 
 If an issue is blocked by another issue, an icon appears next to its title to indicate its blocked
 status.
 
-![Blocked issues](img/issue_boards_blocked_icon_v13_6.png)
+When you hover over the blocked icon (**{issue-block}**), a detailed information popover is displayed.
+
+To enable this in group issue boards, enable the [GraphQL-based sidebar](#graphql-based-sidebar-for-group-issue-boards).
+The feature is enabled by default when you use group issue boards with epic swimlanes.
+
+![Blocked issues](img/issue_boards_blocked_icon_v13_10.png)
 
 ## Actions you can take on an issue board
 

ee/spec/frontend/boards/board_card_inner_spec.js

 import { GlLabel } from '@gitlab/ui';
 import { shallowMount } from '@vue/test-utils';
+import Vuex from 'vuex';
 import IssueCardWeight from 'ee/boards/components/issue_card_weight.vue';
 import BoardCardInner from '~/boards/components/board_card_inner.vue';
+import { issuableTypes } from '~/boards/constants';
 import defaultStore from '~/boards/stores';
 
 describe('Board card component', () => {
   let wrapper;
   let issue;
   let list;
+  let store;
 
-  const createComponent = (props = {}, store = defaultStore) => {
+  const createStore = ({ isShowingLabels = true } = {}) => {
+    store = new Vuex.Store({
+      ...defaultStore,
+      state: {
+        ...defaultStore.state,
+        issuableType: issuableTypes.issue,
+        isShowingLabels,
+      },
+      getters: {
+        isGroupBoard: () => true,
+        isEpicBoard: () => false,
+        isProjectBoard: () => false,
+      },
+    });
+  };
+
+  const createComponent = (props = {}) => {
     wrapper = shallowMount(BoardCardInner, {
       store,
       propsData: {
@@ -55,9 +74,14 @@ describe('Board card component', () => {
     };
   });
 
+  beforeEach(() => {
+    createStore();
+  });
+
   afterEach(() => {
     wrapper.destroy();
     wrapper = null;
+    store = null;
   });
 
   describe('labels', () => {
@@ -95,48 +119,13 @@ describe('Board card component', () => {
     });
 
     it('shows no labels when the isShowingLabels state is false', () => {
-      const store = {
-        ...defaultStore,
-        state: {
-          ...defaultStore.state,
-          isShowingLabels: false,
-        },
-      };
-      createComponent({}, store);
+      createStore({ isShowingLabels: false });
+      createComponent({});
 
       expect(wrapper.findAll('.board-card-labels')).toHaveLength(0);
     });
   });
 
-  describe('blocked', () => {
-    const findBlockedIcon = () => wrapper.find('[data-testid="issue-blocked-icon"');
-
-    it('shows blocked icon if issue is blocked, when blocked by multiple issues', () => {
-      createComponent();
-      const blockedIcon = findBlockedIcon();
-
-      expect(blockedIcon.exists()).toBe(true);
-      expect(blockedIcon.attributes('title')).toBe('Blocked by 2 issues');
-    });
-
-    it('shows blocked icon if issue is blocked, when blocked by one issue', () => {
-      issue.blockedByCount = 1;
-      createComponent();
-      const blockedIcon = findBlockedIcon();
-
-      expect(blockedIcon.exists()).toBe(true);
-      expect(blockedIcon.attributes('title')).toBe('Blocked by 1 issue');
-    });
-
-    it('does not show blocked icon if issue is not blocked', () => {
-      issue.blocked = false;
-      issue.blockedByCount = 0;
-      createComponent();
-
-      expect(findBlockedIcon().exists()).toBe(false);
-    });
-  });
-
   describe('weight', () => {
     it('shows weight component', () => {
       createComponent();

locale/gitlab.pot

@@ -4880,6 +4880,11 @@ msgstr ""
 msgid "Boards and Board Lists"
 msgstr ""
 
+msgid "Boards|+ %{displayedIssuablesCount} more %{issuableType}"
+msgid_plural "Boards|+ %{displayedIssuablesCount} more %{issuableType}s"
+msgstr[0] ""
+msgstr[1] ""
+
 msgid "Boards|An error occurred while creating the issue. Please try again."
 msgstr ""
 
@@ -4922,6 +4927,11 @@ msgstr ""
 msgid "Boards|An error occurred while updating the list. Please try again."
 msgstr ""
 
+msgid "Boards|Blocked by %{blockedByCount} %{issuableType}"
+msgid_plural "Boards|Blocked by %{blockedByCount} %{issuableType}s"
+msgstr[0] ""
+msgstr[1] ""
+
 msgid "Boards|Board"
 msgstr ""
 
@@ -4934,6 +4944,15 @@ msgstr ""
 msgid "Boards|Expand"
 msgstr ""
 
+msgid "Boards|Failed to fetch blocking %{issuableType}s"
+msgstr ""
+
+msgid "Boards|Retrieving blocking %{issuableType}s"
+msgstr ""
+
+msgid "Boards|View all blocking %{issuableType}s"
+msgstr ""
+
 msgid "Boards|View scope"
 msgstr ""
 

spec/frontend/boards/board_card_inner_spec.js

 import { GlLabel } from '@gitlab/ui';
 import { mount } from '@vue/test-utils';
 import { range } from 'lodash';
+import Vuex from 'vuex';
+import BoardBlockedIcon from '~/boards/components/board_blocked_icon.vue';
 import BoardCardInner from '~/boards/components/board_card_inner.vue';
+import { issuableTypes } from '~/boards/constants';
 import eventHub from '~/boards/eventhub';
 import defaultStore from '~/boards/stores';
 import { updateHistory } from '~/lib/utils/url_utility';
-import { mockLabelList } from './mock_data';
+import { mockLabelList, mockIssue } from './mock_data';
 
 jest.mock('~/lib/utils/url_utility');
 jest.mock('~/boards/eventhub');
@@ -29,8 +32,28 @@ describe('Board card component', () => {
   let wrapper;
   let issue;
   let list;
+  let store;
+
+  const findBoardBlockedIcon = () => wrapper.find(BoardBlockedIcon);
+
+  const createStore = () => {
+    store = new Vuex.Store({
+      ...defaultStore,
+      state: {
+        ...defaultStore.state,
+        issuableType: issuableTypes.issue,
+      },
+      getters: {
+        isGroupBoard: () => true,
+        isEpicBoard: () => false,
+        isProjectBoard: () => false,
+      },
+    });
+  };
+
+  const createWrapper = (props = {}) => {
+    createStore();
 
-  const createWrapper = (props = {}, store = defaultStore) => {
     wrapper = mount(BoardCardInner, {
       store,
       propsData: {
@@ -41,6 +64,13 @@ describe('Board card component', () => {
       stubs: {
         GlLabel: true,
       },
+      mocks: {
+        $apollo: {
+          queries: {
+            blockingIssuables: { loading: false },
+          },
+        },
+      },
       provide: {
         rootPath: '/',
         scopedLabelsAvailable: false,
@@ -51,14 +81,9 @@ describe('Board card component', () => {
   beforeEach(() => {
     list = mockLabelList;
     issue = {
-      title: 'Testing',
-      id: 1,
-      iid: 1,
-      confidential: false,
+      ...mockIssue,
       labels: [list.label],
       assignees: [],
-      referencePath: '#1',
-      webUrl: '/test/1',
       weight: 1,
     };
 
@@ -68,6 +93,7 @@ describe('Board card component', () => {
   afterEach(() => {
     wrapper.destroy();
     wrapper = null;
+    store = null;
     jest.clearAllMocks();
   });
 
@@ -87,18 +113,38 @@ describe('Board card component', () => {
     expect(wrapper.find('.confidential-icon').exists()).toBe(false);
   });
 
-  it('does not render blocked icon', () => {
-    expect(wrapper.find('.issue-blocked-icon').exists()).toBe(false);
-  });
-
   it('renders issue ID with #', () => {
-    expect(wrapper.find('.board-card-number').text()).toContain(`#${issue.id}`);
+    expect(wrapper.find('.board-card-number').text()).toContain(`#${issue.iid}`);
   });
 
   it('does not render assignee', () => {
     expect(wrapper.find('.board-card-assignee .avatar').exists()).toBe(false);
   });
 
+  describe('blocked', () => {
+    it('renders blocked icon if issue is blocked', async () => {
+      createWrapper({
+        item: {
+          ...issue,
+          blocked: true,
+        },
+      });
+
+      expect(findBoardBlockedIcon().exists()).toBe(true);
+    });
+
+    it('does not show blocked icon if issue is not blocked', () => {
+      createWrapper({
+        item: {
+          ...issue,
+          blocked: false,
+        },
+      });
+
+      expect(findBoardBlockedIcon().exists()).toBe(false);
+    });
+  });
+
   describe('confidential issue', () => {
     beforeEach(() => {
       wrapper.setProps({
@@ -303,21 +349,6 @@ describe('Board card component', () => {
     });
   });
 
-  describe('blocked', () => {
-    beforeEach(() => {
-      wrapper.setProps({
-        item: {
-          ...wrapper.props('item'),
-          blocked: true,
-        },
-      });
-    });
-
-    it('renders blocked icon if issue is blocked', () => {
-      expect(wrapper.find('.issue-blocked-icon').exists()).toBe(true);
-    });
-  });
-
   describe('filterByLabel method', () => {
     beforeEach(() => {
       delete window.location;

spec/frontend/boards/components/__snapshots__/board_blocked_icon_spec.js.snap

+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`BoardBlockedIcon on mouseenter on blocked icon with more than three blocking issues matches the snapshot 1`] = `
+"<div class=\\"gl-display-inline\\"><svg data-testid=\\"issue-blocked-icon\\" aria-hidden=\\"true\\" class=\\"issue-blocked-icon gl-mr-2 gl-cursor-pointer gl-icon s16\\" id=\\"blocked-icon-uniqueId\\">
+    <use href=\\"#issue-block\\"></use>
+  </svg>
+  <div class=\\"gl-popover\\">
+    <ul class=\\"gl-list-style-none gl-p-0\\">
+      <li><a href=\\"http://gdk.test:3000/gitlab-org/my-project-1/-/issues/6\\" class=\\"gl-link gl-text-blue-500! gl-font-sm\\">my-project-1#6</a>
+        <p data-testid=\\"issuable-title\\" class=\\"gl-mb-3 gl-display-block!\\">
+          blocking issue title 1
+        </p>
+      </li>
+      <li><a href=\\"http://gdk.test:3000/gitlab-org/my-project-1/-/issues/5\\" class=\\"gl-link gl-text-blue-500! gl-font-sm\\">my-project-1#5</a>
+        <p data-testid=\\"issuable-title\\" class=\\"gl-mb-3 gl-display-block!\\">
+          blocking issue title 2 + blocking issue title 2 + blocking issue title 2 + bloc…
+        </p>
+      </li>
+      <li><a href=\\"http://gdk.test:3000/gitlab-org/my-project-1/-/issues/4\\" class=\\"gl-link gl-text-blue-500! gl-font-sm\\">my-project-1#4</a>
+        <p data-testid=\\"issuable-title\\" class=\\"gl-mb-3 gl-display-block!\\">
+          blocking issue title 3
+        </p>
+      </li>
+    </ul>
+    <div class=\\"gl-mt-4\\">
+      <p data-testid=\\"hidden-blocking-count\\" class=\\"gl-mb-3\\">+ 1 more issue</p> <a data-testid=\\"view-all-issues\\" href=\\"http://gdk.test:3000/gitlab-org/my-project-1/-/issues/0#related-issues\\" class=\\"gl-link gl-text-blue-500! gl-font-sm\\">View all blocking issues</a>
+    </div><span data-testid=\\"popover-title\\">Blocked by 4 issues</span>
+  </div>
+</div>"
+`;

spec/frontend/boards/components/board_blocked_icon_spec.js

+import { GlIcon, GlLink, GlPopover, GlLoadingIcon } from '@gitlab/ui';
+import { shallowMount, mount } from '@vue/test-utils';
+import Vue from 'vue';
+import VueApollo from 'vue-apollo';
+import createMockApollo from 'helpers/mock_apollo_helper';
+import { extendedWrapper } from 'helpers/vue_test_utils_helper';
+import waitForPromises from 'helpers/wait_for_promises';
+import BoardBlockedIcon from '~/boards/components/board_blocked_icon.vue';
+import { blockingIssuablesQueries, issuableTypes } from '~/boards/constants';
+import { truncate } from '~/lib/utils/text_utility';
+import {
+  mockIssue,
+  mockBlockingIssue1,
+  mockBlockingIssue2,
+  mockBlockingIssuablesResponse1,
+  mockBlockingIssuablesResponse2,
+  mockBlockingIssuablesResponse3,
+  mockBlockedIssue1,
+  mockBlockedIssue2,
+} from '../mock_data';
+
+describe('BoardBlockedIcon', () => {
+  let wrapper;
+  let mockApollo;
+
+  const findGlIcon = () => wrapper.find(GlIcon);
+  const findGlPopover = () => wrapper.find(GlPopover);
+  const findGlLink = () => wrapper.find(GlLink);
+  const findPopoverTitle = () => wrapper.findByTestId('popover-title');
+  const findIssuableTitle = () => wrapper.findByTestId('issuable-title');
+  const findHiddenBlockingCount = () => wrapper.findByTestId('hidden-blocking-count');
+  const findViewAllIssuableLink = () => wrapper.findByTestId('view-all-issues');
+
+  const waitForApollo = async () => {
+    jest.runOnlyPendingTimers();
+    await waitForPromises();
+  };
+
+  const mouseenter = async () => {
+    findGlIcon().vm.$emit('mouseenter');
+
+    await wrapper.vm.$nextTick();
+    await waitForApollo();
+  };
+
+  afterEach(() => {
+    wrapper.destroy();
+    wrapper = null;
+  });
+
+  const createWrapperWithApollo = ({
+    item = mockBlockedIssue1,
+    blockingIssuablesSpy = jest.fn().mockResolvedValue(mockBlockingIssuablesResponse1),
+  } = {}) => {
+    mockApollo = createMockApollo([
+      [blockingIssuablesQueries[issuableTypes.issue].query, blockingIssuablesSpy],
+    ]);
+
+    Vue.use(VueApollo);
+    wrapper = extendedWrapper(
+      mount(BoardBlockedIcon, {
+        apolloProvider: mockApollo,
+        propsData: {
+          item: {
+            ...mockIssue,
+            ...item,
+          },
+          uniqueId: 'uniqueId',
+          issuableType: issuableTypes.issue,
+        },
+        attachTo: document.body,
+      }),
+    );
+  };
+
+  const createWrapper = ({ item = {}, queries = {}, data = {}, loading = false } = {}) => {
+    wrapper = extendedWrapper(
+      shallowMount(BoardBlockedIcon, {
+        propsData: {
+          item: {
+            ...mockIssue,
+            ...item,
+          },
+          uniqueId: 'uniqueid',
+          issuableType: issuableTypes.issue,
+        },
+        data() {
+          return {
+            ...data,
+          };
+        },
+        mocks: {
+          $apollo: {
+            queries: {
+              blockingIssuables: { loading },
+              ...queries,
+            },
+          },
+        },
+        stubs: {
+          GlPopover,
+        },
+        attachTo: document.body,
+      }),
+    );
+  };
+
+  it('should render blocked icon', () => {
+    createWrapper();
+
+    expect(findGlIcon().exists()).toBe(true);
+  });
+
+  it('should display a loading spinner while loading', () => {
+    createWrapper({ loading: true });
+
+    expect(wrapper.find(GlLoadingIcon).exists()).toBe(true);
+  });
+
+  it('should not query for blocking issuables by default', async () => {
+    createWrapperWithApollo();
+
+    expect(findGlPopover().text()).not.toContain(mockBlockingIssue1.title);
+  });
+
+  describe('on mouseenter on blocked icon', () => {
+    it('should query for blocking issuables and render the result', async () => {
+      createWrapperWithApollo();
+
+      expect(findGlPopover().text()).not.toContain(mockBlockingIssue1.title);
+
+      await mouseenter();
+
+      expect(findGlPopover().exists()).toBe(true);
+      expect(findIssuableTitle().text()).toContain(mockBlockingIssue1.title);
+      expect(wrapper.vm.skip).toBe(true);
+    });
+
+    it('should emit "blocking-issuables-error" event on query error', async () => {
+      const mockError = new Error('mayday');
+      createWrapperWithApollo({ blockingIssuablesSpy: jest.fn().mockRejectedValue(mockError) });
+
+      await mouseenter();
+
+      const [
+        [
+          {
+            message,
+            error: { networkError },
+          },
+        ],
+      ] = wrapper.emitted('blocking-issuables-error');
+      expect(message).toBe('Failed to fetch blocking issues');
+      expect(networkError).toBe(mockError);
+    });
+
+    describe('with a single blocking issue', () => {
+      beforeEach(async () => {
+        createWrapperWithApollo();
+
+        await mouseenter();
+      });
+
+      it('should render a title of the issuable', async () => {
+        expect(findIssuableTitle().text()).toBe(mockBlockingIssue1.title);
+      });
+
+      it('should render issuable reference and link to the issuable', async () => {
+        const formattedRef = mockBlockingIssue1.reference.split('/')[1];
+
+        expect(findGlLink().text()).toBe(formattedRef);
+        expect(findGlLink().attributes('href')).toBe(mockBlockingIssue1.webUrl);
+      });
+
+      it('should render popover title with correct blocking issuable count', async () => {
+        expect(findPopoverTitle().text()).toBe('Blocked by 1 issue');
+      });
+    });
+
+    describe('when issue has a long title', () => {
+      it('should render a truncated title', async () => {
+        createWrapperWithApollo({
+          blockingIssuablesSpy: jest.fn().mockResolvedValue(mockBlockingIssuablesResponse2),
+        });
+
+        await mouseenter();
+
+        const truncatedTitle = truncate(
+          mockBlockingIssue2.title,
+          wrapper.vm.$options.textTruncateWidth,
+        );
+        expect(findIssuableTitle().text()).toBe(truncatedTitle);
+      });
+    });
+
+    describe('with more than three blocking issues', () => {
+      beforeEach(async () => {
+        createWrapperWithApollo({
+          item: mockBlockedIssue2,
+          blockingIssuablesSpy: jest.fn().mockResolvedValue(mockBlockingIssuablesResponse3),
+        });
+
+        await mouseenter();
+      });
+
+      it('matches the snapshot', () => {
+        expect(wrapper.html()).toMatchSnapshot();
+      });
+
+      it('should render popover title with correct blocking issuable count', async () => {
+        expect(findPopoverTitle().text()).toBe('Blocked by 4 issues');
+      });
+
+      it('should render the number of hidden blocking issuables', () => {
+        expect(findHiddenBlockingCount().text()).toBe('+ 1 more issue');
+      });
+
+      it('should link to the blocked issue page at the related issue anchor', async () => {
+        expect(findViewAllIssuableLink().text()).toBe('View all blocking issues');
+        expect(findViewAllIssuableLink().attributes('href')).toBe(
+          `${mockBlockedIssue2.webUrl}#related-issues`,
+        );
+      });
+    });
+  });
+});

spec/frontend/boards/mock_data.js

@@ -398,3 +398,90 @@ export const mockActiveGroupProjects = [
   { ...mockGroupProject1, archived: false },
   { ...mockGroupProject2, archived: false },
 ];
+
+export const mockBlockingIssue1 = {
+  id: 'gid://gitlab/Issue/525',
+  iid: '6',
+  title: 'blocking issue title 1',
+  reference: 'gitlab-org/my-project-1#6',
+  webUrl: 'http://gdk.test:3000/gitlab-org/my-project-1/-/issues/6',
+  __typename: 'Issue',
+};
+
+export const mockBlockingIssue2 = {
+  id: 'gid://gitlab/Issue/524',
+  iid: '5',
+  title:
+    'blocking issue title 2 + blocking issue title 2 + blocking issue title 2 + blocking issue title 2',
+  reference: 'gitlab-org/my-project-1#5',
+  webUrl: 'http://gdk.test:3000/gitlab-org/my-project-1/-/issues/5',
+  __typename: 'Issue',
+};
+
+export const mockBlockingIssue3 = {
+  id: 'gid://gitlab/Issue/523',
+  iid: '4',
+  title: 'blocking issue title 3',
+  reference: 'gitlab-org/my-project-1#4',
+  webUrl: 'http://gdk.test:3000/gitlab-org/my-project-1/-/issues/4',
+  __typename: 'Issue',
+};
+
+export const mockBlockingIssue4 = {
+  id: 'gid://gitlab/Issue/522',
+  iid: '3',
+  title: 'blocking issue title 4',
+  reference: 'gitlab-org/my-project-1#3',
+  webUrl: 'http://gdk.test:3000/gitlab-org/my-project-1/-/issues/3',
+  __typename: 'Issue',
+};
+
+export const mockBlockingIssuablesResponse1 = {
+  data: {
+    issuable: {
+      __typename: 'Issue',
+      id: 'gid://gitlab/Issue/527',
+      blockingIssuables: {
+        __typename: 'IssueConnection',
+        nodes: [mockBlockingIssue1],
+      },
+    },
+  },
+};
+
+export const mockBlockingIssuablesResponse2 = {
+  data: {
+    issuable: {
+      __typename: 'Issue',
+      id: 'gid://gitlab/Issue/527',
+      blockingIssuables: {
+        __typename: 'IssueConnection',
+        nodes: [mockBlockingIssue2],
+      },
+    },
+  },
+};
+
+export const mockBlockingIssuablesResponse3 = {
+  data: {
+    issuable: {
+      __typename: 'Issue',
+      id: 'gid://gitlab/Issue/527',
+      blockingIssuables: {
+        __typename: 'IssueConnection',
+        nodes: [mockBlockingIssue1, mockBlockingIssue2, mockBlockingIssue3, mockBlockingIssue4],
+      },
+    },
+  },
+};
+
+export const mockBlockedIssue1 = {
+  id: '527',
+  blockedByCount: 1,
+};
+
+export const mockBlockedIssue2 = {
+  id: '527',
+  blockedByCount: 4,
+  webUrl: 'http://gdk.test:3000/gitlab-org/my-project-1/-/issues/0',
+};

spec/frontend/boards/stores/actions_spec.js

+import * as Sentry from '@sentry/browser';
 import testAction from 'helpers/vuex_action_helper';
 import {
   fullBoardId,
@@ -1378,6 +1379,51 @@ describe('toggleBoardItem', () => {
   });
 });
 
+describe('setError', () => {
+  it('should commit mutation SET_ERROR', () => {
+    testAction({
+      action: actions.setError,
+      payload: { message: 'mayday' },
+      expectedMutations: [
+        {
+          payload: 'mayday',
+          type: types.SET_ERROR,
+        },
+      ],
+    });
+  });
+
+  it('should capture error using Sentry when captureError is true', () => {
+    jest.spyOn(Sentry, 'captureException');
+
+    const mockError = new Error();
+    actions.setError(
+      { commit: () => {} },
+      {
+        message: 'mayday',
+        error: mockError,
+        captureError: true,
+      },
+    );
+
+    expect(Sentry.captureException).toHaveBeenNthCalledWith(1, mockError);
+  });
+});
+
+describe('unsetError', () => {
+  it('should commit mutation SET_ERROR with undefined as payload', () => {
+    testAction({
+      action: actions.unsetError,
+      expectedMutations: [
+        {
+          payload: undefined,
+          type: types.SET_ERROR,
+        },
+      ],
+    });
+  });
+});
+
 describe('fetchBacklog', () => {
   expectNotImplemented(actions.fetchBacklog);
 });

spec/frontend/boards/stores/mutations_spec.js

@@ -666,4 +666,14 @@ describe('Board Store Mutations', () => {
       expect(state.selectedBoardItems).toEqual([]);
     });
   });
+
+  describe('SET_ERROR', () => {
+    it('Should set error state', () => {
+      state.error = undefined;
+
+      mutations[types.SET_ERROR](state, 'mayday');
+
+      expect(state.error).toBe('mayday');
+    });
+  });
 });