Add Vue ref selector component

Adds a Vue component that allows branches, tags, or commits to be
searched and selected.

app/assets/javascripts/ref/components/ref_results_section.vue

+<script>
+import { GlNewDropdownHeader, GlNewDropdownItem, GlBadge, GlIcon } from '@gitlab/ui';
+import { s__ } from '~/locale';
+
+export default {
+  name: 'RefResultsSection',
+  components: {
+    GlNewDropdownHeader,
+    GlNewDropdownItem,
+    GlBadge,
+    GlIcon,
+  },
+  props: {
+    sectionTitle: {
+      type: String,
+      required: true,
+    },
+
+    totalCount: {
+      type: Number,
+      required: true,
+    },
+
+    /**
+     * An array of object that have the following properties:
+     *
+     * - name (String, required): The name of the ref that will be displayed
+     * - value (String, optional): The value that will be selected when the ref
+     *   is selected. If not provided, `name` will be used as the value.
+     *   For example, commits use the short SHA for `name`
+     *   and long SHA for `value`.
+     * - subtitle (String, optional): Text to render underneath the name.
+     *   For example, used to render the commit's title underneath its SHA.
+     * - default (Boolean, optional): Whether or not to render a "default"
+     *   indicator next to the item. Used to indicate
+     *   the project's default branch.
+     *
+     */
+    items: {
+      type: Array,
+      required: true,
+      validator: items => Array.isArray(items) && items.every(item => item.name),
+    },
+
+    /**
+     * The currently selected ref.
+     * Used to render a check mark by the selected item.
+     * */
+    selectedRef: {
+      type: String,
+      required: false,
+      default: '',
+    },
+
+    /**
+     * An error object that indicates that an error
+     * occurred while fetching items for this section
+     */
+    error: {
+      type: Error,
+      required: false,
+      default: null,
+    },
+
+    /** The message to display if an error occurs */
+    errorMessage: {
+      type: String,
+      required: false,
+      default: '',
+    },
+  },
+  computed: {
+    totalCountText() {
+      return this.totalCount > 999 ? s__('TotalRefCountIndicator|1000+') : `${this.totalCount}`;
+    },
+  },
+  methods: {
+    showCheck(item) {
+      return item.name === this.selectedRef || item.value === this.selectedRef;
+    },
+  },
+};
+</script>
+
+<template>
+  <div>
+    <gl-new-dropdown-header>
+      <div class="gl-display-flex align-items-center" data-testid="section-header">
+        <span class="gl-mr-2 gl-mb-1">{{ sectionTitle }}</span>
+        <gl-badge variant="neutral">{{ totalCountText }}</gl-badge>
+      </div>
+    </gl-new-dropdown-header>
+    <template v-if="error">
+      <div class="gl-display-flex align-items-start text-danger gl-ml-4 gl-mr-4 gl-mb-3">
+        <gl-icon name="error" class="gl-mr-2 gl-mt-2 gl-flex-shrink-0" />
+        <span>{{ errorMessage }}</span>
+      </div>
+    </template>
+    <template v-else>
+      <gl-new-dropdown-item
+        v-for="item in items"
+        :key="item.name"
+        @click="$emit('selected', item.value || item.name)"
+      >
+        <div class="gl-display-flex align-items-start">
+          <gl-icon
+            name="mobile-issue-close"
+            class="gl-mr-2 gl-flex-shrink-0"
+            :class="{ 'gl-visibility-hidden': !showCheck(item) }"
+          />
+
+          <div class="gl-flex-grow-1 gl-display-flex gl-flex-direction-column">
+            <span class="gl-font-monospace">{{ item.name }}</span>
+            <span class="gl-text-gray-600">{{ item.subtitle }}</span>
+          </div>
+
+          <gl-badge v-if="item.default" size="sm" variant="info">{{
+            s__('DefaultBranchLabel|default')
+          }}</gl-badge>
+        </div>
+      </gl-new-dropdown-item>
+    </template>
+  </div>
+</template>

app/assets/javascripts/ref/components/ref_selector.vue

+<script>
+import { mapActions, mapGetters, mapState } from 'vuex';
+import {
+  GlNewDropdown,
+  GlNewDropdownDivider,
+  GlNewDropdownHeader,
+  GlSearchBoxByType,
+  GlSprintf,
+  GlIcon,
+  GlLoadingIcon,
+} from '@gitlab/ui';
+import { debounce } from 'lodash';
+import createStore from '../stores';
+import { SEARCH_DEBOUNCE_MS, DEFAULT_I18N } from '../constants';
+import RefResultsSection from './ref_results_section.vue';
+
+export default {
+  name: 'RefSelector',
+  store: createStore(),
+  components: {
+    GlNewDropdown,
+    GlNewDropdownDivider,
+    GlNewDropdownHeader,
+    GlSearchBoxByType,
+    GlSprintf,
+    GlIcon,
+    GlLoadingIcon,
+    RefResultsSection,
+  },
+  props: {
+    value: {
+      type: String,
+      required: false,
+      default: '',
+    },
+    projectId: {
+      type: String,
+      required: true,
+    },
+    translations: {
+      type: Object,
+      required: false,
+      default: () => ({}),
+    },
+  },
+  data() {
+    return {
+      query: '',
+    };
+  },
+  computed: {
+    ...mapState({
+      matches: state => state.matches,
+      lastQuery: state => state.query,
+      selectedRef: state => state.selectedRef,
+    }),
+    ...mapGetters(['isLoading', 'isQueryPossiblyASha']),
+    i18n() {
+      return {
+        ...DEFAULT_I18N,
+        ...this.translations,
+      };
+    },
+    showBranchesSection() {
+      return Boolean(this.matches.branches.totalCount > 0 || this.matches.branches.error);
+    },
+    showTagsSection() {
+      return Boolean(this.matches.tags.totalCount > 0 || this.matches.tags.error);
+    },
+    showCommitsSection() {
+      return Boolean(this.matches.commits.totalCount > 0 || this.matches.commits.error);
+    },
+    showNoResults() {
+      return !this.showBranchesSection && !this.showTagsSection && !this.showCommitsSection;
+    },
+  },
+  created() {
+    this.setProjectId(this.projectId);
+    this.search(this.query);
+  },
+  methods: {
+    ...mapActions(['setProjectId', 'setSelectedRef', 'search']),
+    focusSearchBox() {
+      this.$refs.searchBox.$el.querySelector('input').focus();
+    },
+    onSearchBoxInput: debounce(function search() {
+      this.search(this.query);
+    }, SEARCH_DEBOUNCE_MS),
+    selectRef(ref) {
+      this.setSelectedRef(ref);
+      this.$emit('input', this.selectedRef);
+    },
+  },
+};
+</script>
+
+<template>
+  <gl-new-dropdown class="ref-selector" @shown="focusSearchBox">
+    <template slot="button-content">
+      <span class="gl-flex-grow-1 gl-ml-2 gl-text-gray-600" data-testid="button-content">
+        <span v-if="selectedRef" class="gl-font-monospace">{{ selectedRef }}</span>
+        <span v-else>{{ i18n.noRefSelected }}</span>
+      </span>
+      <gl-icon name="chevron-down" />
+    </template>
+
+    <div class="gl-display-flex gl-flex-direction-column ref-selector-dropdown-content">
+      <gl-new-dropdown-header>
+        <span class="gl-text-center gl-display-block">{{ i18n.dropdownHeader }}</span>
+      </gl-new-dropdown-header>
+
+      <gl-new-dropdown-divider />
+
+      <gl-search-box-by-type
+        ref="searchBox"
+        v-model.trim="query"
+        class="gl-m-3"
+        :placeholder="i18n.searchPlaceholder"
+        @input="onSearchBoxInput"
+      />
+
+      <div class="gl-flex-grow-1 gl-overflow-y-auto">
+        <gl-loading-icon v-if="isLoading" size="lg" class="gl-my-3" />
+
+        <div
+          v-else-if="showNoResults"
+          class="gl-text-center gl-mx-3 gl-py-3"
+          data-testid="no-results"
+        >
+          <gl-sprintf v-if="lastQuery" :message="i18n.noResultsWithQuery">
+            <template #query>
+              <b class="gl-word-break-all">{{ lastQuery }}</b>
+            </template>
+          </gl-sprintf>
+
+          <span v-else>{{ i18n.noResults }}</span>
+        </div>
+
+        <template v-else>
+          <template v-if="showBranchesSection">
+            <ref-results-section
+              :section-title="i18n.branches"
+              :total-count="matches.branches.totalCount"
+              :items="matches.branches.list"
+              :selected-ref="selectedRef"
+              :error="matches.branches.error"
+              :error-message="i18n.branchesErrorMessage"
+              data-testid="branches-section"
+              @selected="selectRef($event)"
+            />
+
+            <gl-new-dropdown-divider v-if="showTagsSection || showCommitsSection" />
+          </template>
+
+          <template v-if="showTagsSection">
+            <ref-results-section
+              :section-title="i18n.tags"
+              :total-count="matches.tags.totalCount"
+              :items="matches.tags.list"
+              :selected-ref="selectedRef"
+              :error="matches.tags.error"
+              :error-message="i18n.tagsErrorMessage"
+              data-testid="tags-section"
+              @selected="selectRef($event)"
+            />
+
+            <gl-new-dropdown-divider v-if="showCommitsSection" />
+          </template>
+
+          <template v-if="showCommitsSection">
+            <ref-results-section
+              :section-title="i18n.commits"
+              :total-count="matches.commits.totalCount"
+              :items="matches.commits.list"
+              :selected-ref="selectedRef"
+              :error="matches.commits.error"
+              :error-message="i18n.commitsErrorMessage"
+              data-testid="commits-section"
+              @selected="selectRef($event)"
+            />
+          </template>
+        </template>
+      </div>
+    </div>
+  </gl-new-dropdown>
+</template>

app/assets/javascripts/ref/constants.js

-// This eslint-disable can be removed once a second
-// value is added to this file.
-/* eslint-disable import/prefer-default-export */
+import { __ } from '~/locale';
+
 export const X_TOTAL_HEADER = 'x-total';
+
+export const SEARCH_DEBOUNCE_MS = 250;
+
+export const DEFAULT_I18N = Object.freeze({
+  dropdownHeader: __('Select Git revision'),
+  searchPlaceholder: __('Search by Git revision'),
+  noResultsWithQuery: __('No matching results for "%{query}"'),
+  noResults: __('No matching results'),
+  branchesErrorMessage: __('An error occurred while fetching branches.  Retry the search.'),
+  tagsErrorMessage: __('An error occurred while fetching tags. Retry the search.'),
+  commitsErrorMessage: __('An error occurred while fetching commits.  Retry the search.'),
+  branches: __('Branches'),
+  tags: __('Tags'),
+  commits: __('Commits'),
+  noRefSelected: __('No ref selected'),
+});

app/assets/stylesheets/components/ref_selector.scss

+.ref-selector {
+  & &-dropdown-content {
+    // Setting a max height is necessary to allow the dropdown's content
+    // to control where and how scrollbars appear.
+    // This content is limited to the max-height of the dropdown
+    // ($dropdown-max-height-lg) minus the additional padding
+    // on the top and bottom (2 * $gl-padding-8)
+    max-height: $dropdown-max-height-lg - 2 * $gl-padding-8;
+  }
+
+  .dropdown-menu.show {
+    // Make the dropdown a little wider and longer than usual
+    // since it contains quite a bit of content.
+    width: 20rem;
+    max-height: $dropdown-max-height-lg;
+  }
+}

locale/gitlab.pot

@@ -2475,6 +2475,12 @@ msgstr ""
 msgid "An error occurred while enabling Service Desk."
 msgstr ""
 
+msgid "An error occurred while fetching branches.  Retry the search."
+msgstr ""
+
+msgid "An error occurred while fetching commits.  Retry the search."
+msgstr ""
+
 msgid "An error occurred while fetching coverage reports."
 msgstr ""
 
@@ -2505,6 +2511,9 @@ msgstr ""
 msgid "An error occurred while fetching sidebar data"
 msgstr ""
 
+msgid "An error occurred while fetching tags. Retry the search."
+msgstr ""
+
 msgid "An error occurred while fetching terraform reports."
 msgstr ""
 
@@ -7441,6 +7450,9 @@ msgstr ""
 msgid "Default: Map a FogBugz account ID to a full name"
 msgstr ""
 
+msgid "DefaultBranchLabel|default"
+msgstr ""
+
 msgid "Define a custom pattern with cron syntax"
 msgstr ""
 
@@ -15598,6 +15610,9 @@ msgstr ""
 msgid "No matching results"
 msgstr ""
 
+msgid "No matching results for \"%{query}\""
+msgstr ""
+
 msgid "No merge requests found"
 msgstr ""
 
@@ -15634,6 +15649,9 @@ msgstr ""
 msgid "No public groups"
 msgstr ""
 
+msgid "No ref selected"
+msgstr ""
+
 msgid "No related merge requests found."
 msgstr ""
 
@@ -20253,6 +20271,9 @@ msgstr ""
 msgid "Search branches and tags"
 msgstr ""
 
+msgid "Search by Git revision"
+msgstr ""
+
 msgid "Search by author"
 msgstr ""
 
@@ -24632,6 +24653,9 @@ msgstr ""
 msgid "Total: %{total}"
 msgstr ""
 
+msgid "TotalRefCountIndicator|1000+"
+msgstr ""
+
 msgid "Trace"
 msgstr ""
 

spec/frontend/ref/components/ref_selector_spec.js

+import Vuex from 'vuex';
+import { mount, createLocalVue } from '@vue/test-utils';
+import axios from 'axios';
+import MockAdapter from 'axios-mock-adapter';
+import { GlLoadingIcon, GlSearchBoxByType, GlNewDropdownItem, GlIcon } from '@gitlab/ui';
+import { trimText } from 'helpers/text_helper';
+import { sprintf } from '~/locale';
+import RefSelector from '~/ref/components/ref_selector.vue';
+import { X_TOTAL_HEADER, DEFAULT_I18N } from '~/ref/constants';
+import createStore from '~/ref/stores/';
+
+const localVue = createLocalVue();
+localVue.use(Vuex);
+
+describe('Ref selector component', () => {
+  const fixtures = {
+    branches: getJSONFixture('api/branches/branches.json'),
+    tags: getJSONFixture('api/tags/tags.json'),
+    commit: getJSONFixture('api/commits/commit.json'),
+  };
+
+  const projectId = '8';
+
+  let wrapper;
+  let branchesApiCallSpy;
+  let tagsApiCallSpy;
+  let commitApiCallSpy;
+
+  const createComponent = () => {
+    wrapper = mount(RefSelector, {
+      propsData: {
+        projectId,
+        value: '',
+      },
+      listeners: {
+        // simulate a parent component v-model binding
+        input: selectedRef => {
+          wrapper.setProps({ value: selectedRef });
+        },
+      },
+      stubs: {
+        GlSearchBoxByType: true,
+      },
+      localVue,
+      store: createStore(),
+    });
+  };
+
+  beforeEach(() => {
+    const mock = new MockAdapter(axios);
+    gon.api_version = 'v4';
+
+    branchesApiCallSpy = jest
+      .fn()
+      .mockReturnValue([200, fixtures.branches, { [X_TOTAL_HEADER]: '123' }]);
+    tagsApiCallSpy = jest.fn().mockReturnValue([200, fixtures.tags, { [X_TOTAL_HEADER]: '456' }]);
+    commitApiCallSpy = jest.fn().mockReturnValue([200, fixtures.commit]);
+
+    mock
+      .onGet(`/api/v4/projects/${projectId}/repository/branches`)
+      .reply(config => branchesApiCallSpy(config));
+    mock
+      .onGet(`/api/v4/projects/${projectId}/repository/tags`)
+      .reply(config => tagsApiCallSpy(config));
+    mock
+      .onGet(new RegExp(`/api/v4/projects/${projectId}/repository/commits/.*`))
+      .reply(config => commitApiCallSpy(config));
+  });
+
+  afterEach(() => {
+    wrapper.destroy();
+    wrapper = null;
+  });
+
+  //
+  // Finders
+  //
+  const findButtonContent = () => wrapper.find('[data-testid="button-content"]');
+
+  const findNoResults = () => wrapper.find('[data-testid="no-results"]');
+
+  const findLoadingIcon = () => wrapper.find(GlLoadingIcon);
+
+  const findBranchesSection = () => wrapper.find('[data-testid="branches-section"]');
+  const findBranchDropdownItems = () => findBranchesSection().findAll(GlNewDropdownItem);
+  const findFirstBranchDropdownItem = () => findBranchDropdownItems().at(0);
+
+  const findTagsSection = () => wrapper.find('[data-testid="tags-section"]');
+  const findTagDropdownItems = () => findTagsSection().findAll(GlNewDropdownItem);
+  const findFirstTagDropdownItem = () => findTagDropdownItems().at(0);
+
+  const findCommitsSection = () => wrapper.find('[data-testid="commits-section"]');
+  const findCommitDropdownItems = () => findCommitsSection().findAll(GlNewDropdownItem);
+  const findFirstCommitDropdownItem = () => findCommitDropdownItems().at(0);
+
+  //
+  // Expecters
+  //
+  const branchesSectionContainsErrorMessage = () => {
+    const branchesSection = findBranchesSection();
+
+    return branchesSection.text().includes(DEFAULT_I18N.branchesErrorMessage);
+  };
+
+  const tagsSectionContainsErrorMessage = () => {
+    const tagsSection = findTagsSection();
+
+    return tagsSection.text().includes(DEFAULT_I18N.tagsErrorMessage);
+  };
+
+  const commitsSectionContainsErrorMessage = () => {
+    const commitsSection = findCommitsSection();
+
+    return commitsSection.text().includes(DEFAULT_I18N.commitsErrorMessage);
+  };
+
+  //
+  // Convenience methods
+  //
+  const updateQuery = newQuery => {
+    wrapper.find(GlSearchBoxByType).vm.$emit('input', newQuery);
+  };
+
+  const selectFirstBranch = () => {
+    findFirstBranchDropdownItem().vm.$emit('click');
+  };
+
+  const selectFirstTag = () => {
+    findFirstTagDropdownItem().vm.$emit('click');
+  };
+
+  const selectFirstCommit = () => {
+    findFirstCommitDropdownItem().vm.$emit('click');
+  };
+
+  const waitForRequests = ({ andClearMocks } = { andClearMocks: false }) =>
+    axios.waitForAll().then(() => {
+      if (andClearMocks) {
+        branchesApiCallSpy.mockClear();
+        tagsApiCallSpy.mockClear();
+        commitApiCallSpy.mockClear();
+      }
+    });
+
+  describe('initialization behavior', () => {
+    beforeEach(createComponent);
+
+    it('initializes the dropdown with branches and tags when mounted', () => {
+      return waitForRequests().then(() => {
+        expect(branchesApiCallSpy).toHaveBeenCalledTimes(1);
+        expect(tagsApiCallSpy).toHaveBeenCalledTimes(1);
+        expect(commitApiCallSpy).not.toHaveBeenCalled();
+      });
+    });
+
+    it('shows a spinner while network requests are in progress', () => {
+      expect(findLoadingIcon().exists()).toBe(true);
+
+      return waitForRequests().then(() => {
+        expect(findLoadingIcon().exists()).toBe(false);
+      });
+    });
+  });
+
+  describe('post-initialization behavior', () => {
+    describe('when the search query is updated', () => {
+      beforeEach(() => {
+        createComponent();
+
+        return waitForRequests({ andClearMocks: true });
+      });
+
+      it('requeries the endpoints when the search query is updated', () => {
+        updateQuery('v1.2.3');
+
+        return waitForRequests().then(() => {
+          expect(branchesApiCallSpy).toHaveBeenCalledTimes(1);
+          expect(tagsApiCallSpy).toHaveBeenCalledTimes(1);
+        });
+      });
+
+      it("does not make a call to the commit endpoint if the query doesn't look like a SHA", () => {
+        updateQuery('not a sha');
+
+        return waitForRequests().then(() => {
+          expect(commitApiCallSpy).not.toHaveBeenCalled();
+        });
+      });
+
+      it('searches for a commit if the query could potentially be a SHA', () => {
+        updateQuery('abcdef');
+
+        return waitForRequests().then(() => {
+          expect(commitApiCallSpy).toHaveBeenCalled();
+        });
+      });
+    });
+
+    describe('when no results are found', () => {
+      beforeEach(() => {
+        branchesApiCallSpy = jest.fn().mockReturnValue([200, [], { [X_TOTAL_HEADER]: '0' }]);
+        tagsApiCallSpy = jest.fn().mockReturnValue([200, [], { [X_TOTAL_HEADER]: '0' }]);
+        commitApiCallSpy = jest.fn().mockReturnValue([404]);
+
+        createComponent();
+
+        return waitForRequests();
+      });
+
+      describe('when the search query is empty', () => {
+        it('renders a "no results" message', () => {
+          expect(findNoResults().text()).toBe(DEFAULT_I18N.noResults);
+        });
+      });
+
+      describe('when the search query is not empty', () => {
+        const query = 'hello';
+
+        beforeEach(() => {
+          updateQuery(query);
+
+          return waitForRequests();
+        });
+
+        it('renders a "no results" message that includes the search query', () => {
+          expect(findNoResults().text()).toBe(sprintf(DEFAULT_I18N.noResultsWithQuery, { query }));
+        });
+      });
+    });
+
+    describe('branches', () => {
+      describe('when the branches search returns results', () => {
+        beforeEach(() => {
+          createComponent();
+
+          return waitForRequests();
+        });
+
+        it('renders the branches section in the dropdown', () => {
+          expect(findBranchesSection().exists()).toBe(true);
+        });
+
+        it('renders the "Branches" heading with a total number indicator', () => {
+          expect(
+            findBranchesSection()
+              .find('[data-testid="section-header"]')
+              .text(),
+          ).toBe('Branches 123');
+        });
+
+        it("does not render an error message in the branches section's body", () => {
+          expect(branchesSectionContainsErrorMessage()).toBe(false);
+        });
+
+        it('renders each non-default branch as a selectable item', () => {
+          const dropdownItems = findBranchDropdownItems();
+
+          fixtures.branches.forEach((b, i) => {
+            if (!b.default) {
+              expect(dropdownItems.at(i).text()).toBe(b.name);
+            }
+          });
+        });
+
+        it('renders the default branch as a selectable item with a "default" badge', () => {
+          const dropdownItems = findBranchDropdownItems();
+
+          const defaultBranch = fixtures.branches.find(b => b.default);
+          const defaultBranchIndex = fixtures.branches.indexOf(defaultBranch);
+
+          expect(trimText(dropdownItems.at(defaultBranchIndex).text())).toBe(
+            `${defaultBranch.name} default`,
+          );
+        });
+      });
+
+      describe('when the branches search returns no results', () => {
+        beforeEach(() => {
+          branchesApiCallSpy = jest.fn().mockReturnValue([200, [], { [X_TOTAL_HEADER]: '0' }]);
+
+          createComponent();
+
+          return waitForRequests();
+        });
+
+        it('does not render the branches section in the dropdown', () => {
+          expect(findBranchesSection().exists()).toBe(false);
+        });
+      });
+
+      describe('when the branches search returns an error', () => {
+        beforeEach(() => {
+          branchesApiCallSpy = jest.fn().mockReturnValue([500]);
+
+          createComponent();
+
+          return waitForRequests();
+        });
+
+        it('renders the branches section in the dropdown', () => {
+          expect(findBranchesSection().exists()).toBe(true);
+        });
+
+        it("renders an error message in the branches section's body", () => {
+          expect(branchesSectionContainsErrorMessage()).toBe(true);
+        });
+      });
+    });
+
+    describe('tags', () => {
+      describe('when the tags search returns results', () => {
+        beforeEach(() => {
+          createComponent();
+
+          return waitForRequests();
+        });
+
+        it('renders the tags section in the dropdown', () => {
+          expect(findTagsSection().exists()).toBe(true);
+        });
+
+        it('renders the "Tags" heading with a total number indicator', () => {
+          expect(
+            findTagsSection()
+              .find('[data-testid="section-header"]')
+              .text(),
+          ).toBe('Tags 456');
+        });
+
+        it("does not render an error message in the tags section's body", () => {
+          expect(tagsSectionContainsErrorMessage()).toBe(false);
+        });
+
+        it('renders each tag as a selectable item', () => {
+          const dropdownItems = findTagDropdownItems();
+
+          fixtures.tags.forEach((t, i) => {
+            expect(dropdownItems.at(i).text()).toBe(t.name);
+          });
+        });
+      });
+
+      describe('when the tags search returns no results', () => {
+        beforeEach(() => {
+          tagsApiCallSpy = jest.fn().mockReturnValue([200, [], { [X_TOTAL_HEADER]: '0' }]);
+
+          createComponent();
+
+          return waitForRequests();
+        });
+
+        it('does not render the tags section in the dropdown', () => {
+          expect(findTagsSection().exists()).toBe(false);
+        });
+      });
+
+      describe('when the tags search returns an error', () => {
+        beforeEach(() => {
+          tagsApiCallSpy = jest.fn().mockReturnValue([500]);
+
+          createComponent();
+
+          return waitForRequests();
+        });
+
+        it('renders the tags section in the dropdown', () => {
+          expect(findTagsSection().exists()).toBe(true);
+        });
+
+        it("renders an error message in the tags section's body", () => {
+          expect(tagsSectionContainsErrorMessage()).toBe(true);
+        });
+      });
+    });
+
+    describe('commits', () => {
+      describe('when the commit search returns results', () => {
+        beforeEach(() => {
+          createComponent();
+
+          updateQuery('abcd1234');
+
+          return waitForRequests();
+        });
+
+        it('renders the commit section in the dropdown', () => {
+          expect(findCommitsSection().exists()).toBe(true);
+        });
+
+        it('renders the "Commits" heading with a total number indicator', () => {
+          expect(
+            findCommitsSection()
+              .find('[data-testid="section-header"]')
+              .text(),
+          ).toBe('Commits 1');
+        });
+
+        it("does not render an error message in the comits section's body", () => {
+          expect(commitsSectionContainsErrorMessage()).toBe(false);
+        });
+
+        it('renders each commit as a selectable item with the short SHA and commit title', () => {
+          const dropdownItems = findCommitDropdownItems();
+
+          const { commit } = fixtures;
+
+          expect(dropdownItems.at(0).text()).toBe(`${commit.short_id} ${commit.title}`);
+        });
+      });
+
+      describe('when the commit search returns no results (i.e. a 404)', () => {
+        beforeEach(() => {
+          commitApiCallSpy = jest.fn().mockReturnValue([404]);
+
+          createComponent();
+
+          updateQuery('abcd1234');
+
+          return waitForRequests();
+        });
+
+        it('does not render the commits section in the dropdown', () => {
+          expect(findCommitsSection().exists()).toBe(false);
+        });
+      });
+
+      describe('when the commit search returns an error (other than a 404)', () => {
+        beforeEach(() => {
+          commitApiCallSpy = jest.fn().mockReturnValue([500]);
+
+          createComponent();
+
+          updateQuery('abcd1234');
+
+          return waitForRequests();
+        });
+
+        it('renders the commits section in the dropdown', () => {
+          expect(findCommitsSection().exists()).toBe(true);
+        });
+
+        it("renders an error message in the commits section's body", () => {
+          expect(commitsSectionContainsErrorMessage()).toBe(true);
+        });
+      });
+    });
+
+    describe('selection', () => {
+      beforeEach(() => {
+        createComponent();
+
+        updateQuery(fixtures.commit.short_id);
+
+        return waitForRequests();
+      });
+
+      it('renders a checkmark by the selected item', () => {
+        expect(findFirstBranchDropdownItem().find(GlIcon).element).toHaveClass(
+          'gl-visibility-hidden',
+        );
+
+        selectFirstBranch();
+
+        return localVue.nextTick().then(() => {
+          expect(findFirstBranchDropdownItem().find(GlIcon).element).not.toHaveClass(
+            'gl-visibility-hidden',
+          );
+        });
+      });
+
+      describe('when a branch is seleceted', () => {
+        it("displays the branch name in the dropdown's button", () => {
+          expect(findButtonContent().text()).toBe(DEFAULT_I18N.noRefSelected);
+
+          selectFirstBranch();
+
+          return localVue.nextTick().then(() => {
+            expect(findButtonContent().text()).toBe(fixtures.branches[0].name);
+          });
+        });
+
+        it("updates the v-model binding with the branch's name", () => {
+          expect(wrapper.vm.value).toEqual('');
+
+          selectFirstBranch();
+
+          expect(wrapper.vm.value).toEqual(fixtures.branches[0].name);
+        });
+      });
+
+      describe('when a tag is seleceted', () => {
+        it("displays the tag name in the dropdown's button", () => {
+          expect(findButtonContent().text()).toBe(DEFAULT_I18N.noRefSelected);
+
+          selectFirstTag();
+
+          return localVue.nextTick().then(() => {
+            expect(findButtonContent().text()).toBe(fixtures.tags[0].name);
+          });
+        });
+
+        it("updates the v-model binding with the tag's name", () => {
+          expect(wrapper.vm.value).toEqual('');
+
+          selectFirstTag();
+
+          expect(wrapper.vm.value).toEqual(fixtures.tags[0].name);
+        });
+      });
+
+      describe('when a commit is selected', () => {
+        it("displays the full SHA in the dropdown's button", () => {
+          expect(findButtonContent().text()).toBe(DEFAULT_I18N.noRefSelected);
+
+          selectFirstCommit();
+
+          return localVue.nextTick().then(() => {
+            expect(findButtonContent().text()).toBe(fixtures.commit.id);
+          });
+        });
+
+        it("updates the v-model binding with the commit's full SHA", () => {
+          expect(wrapper.vm.value).toEqual('');
+
+          selectFirstCommit();
+
+          expect(wrapper.vm.value).toEqual(fixtures.commit.id);
+        });
+      });
+    });
+  });
+});