From 088b0f25ca83e8932b47a439b407a7ee9db177c0 Mon Sep 17 00:00:00 2001
From: jboyson1 <jboyson@gitlab.com>
Date: Wed, 8 Apr 2020 11:19:24 -0500
Subject: [PATCH] Add line_range support to frontend

Add dropdown start line selector to diff_line_note_form.vue
Pass line_range to saveDiffDiscussion action
---
 .../batch_comments/components/draft_note.vue  | 12 +++
 .../components/inline_draft_comment_row.vue   | 11 ++-
 .../components/preview_item.vue               | 51 ++++++++++--
 .../batch_comments/services/drafts_service.js |  4 +-
 .../stores/modules/batch_comments/actions.js  |  6 +-
 .../diffs/components/diff_line_note_form.vue  | 36 +++++++-
 .../diffs/components/inline_diff_view.vue     |  2 +
 app/assets/javascripts/diffs/store/utils.js   |  2 +
 .../components/multiline_comment_form.vue     | 68 +++++++++++++++
 .../components/multiline_comment_utils.js     | 57 +++++++++++++
 .../notes/components/noteable_note.vue        | 82 ++++++++++++++++++-
 .../projects/merge_requests_controller.rb     |  1 +
 .../unreleased/jdb-mutliline-comment-fe.yml   |  5 ++
 doc/api/discussions.md                        |  6 +-
 lib/api/discussions.rb                        |  2 +
 locale/gitlab.pot                             | 12 +++
 .../user_comments_on_diff_spec.rb             | 34 ++++++++
 .../components/diff_line_note_form_spec.js    | 14 +++-
 spec/frontend/diffs/store/actions_spec.js     |  2 +-
 spec/frontend/diffs/store/utils_spec.js       |  2 +
 .../multiline_comment_utils_spec.js           | 49 +++++++++++
 .../notes/components/noteable_note_spec.js    | 53 +++++++++++-
 ..._on_merge_request_files_shared_examples.rb |  1 +
 .../api/diff_discussions_shared_examples.rb   |  4 +-
 24 files changed, 496 insertions(+), 20 deletions(-)
 create mode 100644 app/assets/javascripts/notes/components/multiline_comment_form.vue
 create mode 100644 app/assets/javascripts/notes/components/multiline_comment_utils.js
 create mode 100644 changelogs/unreleased/jdb-mutliline-comment-fe.yml
 create mode 100644 spec/frontend/notes/components/multiline_comment_utils_spec.js

diff --git a/app/assets/javascripts/batch_comments/components/draft_note.vue b/app/assets/javascripts/batch_comments/components/draft_note.vue
index 3e0ae6f65c62e1..963d104b6b3720 100644
--- a/app/assets/javascripts/batch_comments/components/draft_note.vue
+++ b/app/assets/javascripts/batch_comments/components/draft_note.vue
@@ -15,6 +15,16 @@ export default {
       type: Object,
       required: true,
     },
+    diffFile: {
+      type: Object,
+      required: false,
+      default: () => ({}),
+    },
+    line: {
+      type: Object,
+      required: false,
+      default: null,
+    },
   },
   data() {
     return {
@@ -61,6 +71,8 @@ export default {
     <ul class="notes draft-notes">
       <noteable-note
         :note="draft"
+        :diff-lines="diffFile.highlighted_diff_lines"
+        :line="line"
         class="draft-note"
         @handleEdit="handleEditing"
         @cancelForm="handleNotEditing"
diff --git a/app/assets/javascripts/batch_comments/components/inline_draft_comment_row.vue b/app/assets/javascripts/batch_comments/components/inline_draft_comment_row.vue
index b7c9831dd45422..385725cd109200 100644
--- a/app/assets/javascripts/batch_comments/components/inline_draft_comment_row.vue
+++ b/app/assets/javascripts/batch_comments/components/inline_draft_comment_row.vue
@@ -10,6 +10,15 @@ export default {
       type: Object,
       required: true,
     },
+    diffFile: {
+      type: Object,
+      required: true,
+    },
+    line: {
+      type: Object,
+      required: false,
+      default: null,
+    },
   },
 };
 </script>
@@ -17,7 +26,7 @@ export default {
 <template>
   <tr class="notes_holder js-temp-notes-holder">
     <td class="notes-content" colspan="4">
-      <div class="content"><draft-note :draft="draft" /></div>
+      <div class="content"><draft-note :draft="draft" :diff-file="diffFile" :line="line" /></div>
     </td>
   </tr>
 </template>
diff --git a/app/assets/javascripts/batch_comments/components/preview_item.vue b/app/assets/javascripts/batch_comments/components/preview_item.vue
index df9c419ff96f94..22495eb4d7d052 100644
--- a/app/assets/javascripts/batch_comments/components/preview_item.vue
+++ b/app/assets/javascripts/batch_comments/components/preview_item.vue
@@ -4,12 +4,20 @@ import { IMAGE_DIFF_POSITION_TYPE } from '~/diffs/constants';
 import { sprintf, __ } from '~/locale';
 import Icon from '~/vue_shared/components/icon.vue';
 import resolvedStatusMixin from '../mixins/resolved_status';
+import { GlSprintf } from '@gitlab/ui';
+import glFeatureFlagsMixin from '~/vue_shared/mixins/gl_feature_flags_mixin';
+import {
+  getStartLineNumber,
+  getEndLineNumber,
+  getLineClasses,
+} from '~/notes/components/multiline_comment_utils';
 
 export default {
   components: {
     Icon,
+    GlSprintf,
   },
-  mixins: [resolvedStatusMixin],
+  mixins: [resolvedStatusMixin, glFeatureFlagsMixin()],
   props: {
     draft: {
       type: Object,
@@ -51,7 +59,7 @@ export default {
 
       const position = this.discussion ? this.discussion.position : this.draft.position;
 
-      return position.new_line || position.old_line;
+      return position?.new_line || position?.old_line;
     },
     content() {
       const el = document.createElement('div');
@@ -62,9 +70,18 @@ export default {
     showLinePosition() {
       return this.draft.file_hash || this.isDiffDiscussion;
     },
+    startLineNumber() {
+      return getStartLineNumber(this.draft.position?.line_range);
+    },
+    endLineNumber() {
+      return getEndLineNumber(this.draft.position?.line_range);
+    },
   },
   methods: {
     ...mapActions('batchComments', ['scrollToDraft']),
+    getLineClasses(lineNumber) {
+      return getLineClasses(lineNumber);
+    },
   },
   showStaysResolved: false,
 };
@@ -83,11 +100,33 @@ export default {
     @click="scrollToDraft(draft)"
   >
     <span class="review-preview-item-header">
-      <icon class="gl-mr-3 flex-shrink-0" :name="iconName" />
-      <span class="bold text-nowrap">
-        <span class="review-preview-item-header-text block-truncated"> {{ titleText }} </span>
+      <icon class="flex-shrink-0" :name="iconName" />
+      <span
+        class="bold text-nowrap"
+        :class="{ 'gl-align-items-center': glFeatures.multilineComments }"
+      >
+        <span class="review-preview-item-header-text block-truncated">
+          {{ titleText }}
+        </span>
         <template v-if="showLinePosition">
-          :{{ linePosition }}
+          <template v-if="!glFeatures.multilineComments"
+            >:{{ linePosition }}</template
+          >
+          <template v-else-if="startLineNumber === endLineNumber">
+            :<span :class="getLineClasses(startLineNumber)">{{ startLineNumber }}</span>
+          </template>
+          <gl-sprintf v-else :message="__(':%{startLine} to %{endLine}')">
+            <template #startLine>
+              <span class="gl-mr-2" :class="getLineClasses(startLineNumber)">{{
+                startLineNumber
+              }}</span>
+            </template>
+            <template #endLine>
+              <span class="gl-ml-2" :class="getLineClasses(endLineNumber)">{{
+                endLineNumber
+              }}</span>
+            </template>
+          </gl-sprintf>
         </template>
       </span>
     </span>
diff --git a/app/assets/javascripts/batch_comments/services/drafts_service.js b/app/assets/javascripts/batch_comments/services/drafts_service.js
index e81b48cd873aa9..36d2f8df612c61 100644
--- a/app/assets/javascripts/batch_comments/services/drafts_service.js
+++ b/app/assets/javascripts/batch_comments/services/drafts_service.js
@@ -25,9 +25,9 @@ export default {
   discard(endpoint) {
     return axios.delete(endpoint);
   },
-  update(endpoint, { draftId, note, resolveDiscussion }) {
+  update(endpoint, { draftId, note, resolveDiscussion, position }) {
     return axios.put(`${endpoint}/${draftId}`, {
-      draft_note: { note, resolve_discussion: resolveDiscussion },
+      draft_note: { note, resolve_discussion: resolveDiscussion, position },
     });
   },
 };
diff --git a/app/assets/javascripts/batch_comments/stores/modules/batch_comments/actions.js b/app/assets/javascripts/batch_comments/stores/modules/batch_comments/actions.js
index ae3d5161665711..1ef012696c5279 100644
--- a/app/assets/javascripts/batch_comments/stores/modules/batch_comments/actions.js
+++ b/app/assets/javascripts/batch_comments/stores/modules/batch_comments/actions.js
@@ -84,12 +84,16 @@ export const discardReview = ({ commit, getters }) => {
     .catch(() => commit(types.RECEIVE_DISCARD_REVIEW_ERROR));
 };
 
-export const updateDraft = ({ commit, getters }, { note, noteText, resolveDiscussion, callback }) =>
+export const updateDraft = (
+  { commit, getters },
+  { note, noteText, resolveDiscussion, position, callback },
+) =>
   service
     .update(getters.getNotesData.draftsPath, {
       draftId: note.id,
       note: noteText,
       resolveDiscussion,
+      position: JSON.stringify(position),
     })
     .then(res => res.data)
     .then(data => commit(types.RECEIVE_DRAFT_UPDATE_SUCCESS, data))
diff --git a/app/assets/javascripts/diffs/components/diff_line_note_form.vue b/app/assets/javascripts/diffs/components/diff_line_note_form.vue
index a94c85001a42df..74305ee69bc4f2 100644
--- a/app/assets/javascripts/diffs/components/diff_line_note_form.vue
+++ b/app/assets/javascripts/diffs/components/diff_line_note_form.vue
@@ -1,18 +1,22 @@
 <script>
 import { mapState, mapGetters, mapActions } from 'vuex';
 import diffLineNoteFormMixin from '~/notes/mixins/diff_line_note_form';
+import glFeatureFlagsMixin from '~/vue_shared/mixins/gl_feature_flags_mixin';
 import { s__ } from '~/locale';
 import noteForm from '../../notes/components/note_form.vue';
+import MultilineCommentForm from '../../notes/components/multiline_comment_form.vue';
 import autosave from '../../notes/mixins/autosave';
 import userAvatarLink from '../../vue_shared/components/user_avatar/user_avatar_link.vue';
 import { DIFF_NOTE_TYPE } from '../constants';
+import { commentLineOptions } from '../../notes/components/multiline_comment_utils';
 
 export default {
   components: {
     noteForm,
     userAvatarLink,
+    MultilineCommentForm,
   },
-  mixins: [autosave, diffLineNoteFormMixin],
+  mixins: [autosave, diffLineNoteFormMixin, glFeatureFlagsMixin()],
   props: {
     diffFileHash: {
       type: String,
@@ -37,6 +41,14 @@ export default {
       default: '',
     },
   },
+  data() {
+    return {
+      commentLineStart: {
+        lineCode: this.line.line_code,
+        type: this.line.type,
+      },
+    };
+  },
   computed: {
     ...mapState({
       noteableData: state => state.notes.noteableData,
@@ -62,11 +74,20 @@ export default {
         diffViewType: this.diffViewType,
         diffFile: this.diffFile,
         linePosition: this.linePosition,
+        lineRange: {
+          start_line_code: this.commentLineStart.lineCode,
+          start_line_type: this.commentLineStart.type,
+          end_line_code: this.line.line_code,
+          end_line_type: this.line.type,
+        },
       };
     },
     diffFile() {
       return this.getDiffFileByHash(this.diffFileHash);
     },
+    commentLineOptions() {
+      return commentLineOptions(this.diffFile.highlighted_diff_lines, this.line.line_code);
+    },
   },
   mounted() {
     if (this.isLoggedIn) {
@@ -83,7 +104,6 @@ export default {
   methods: {
     ...mapActions('diffs', [
       'cancelCommentForm',
-      'assignDiscussionsToDiff',
       'saveDiffDiscussion',
       'setSuggestPopoverDismissed',
     ]),
@@ -116,6 +136,16 @@ export default {
 
 <template>
   <div class="content discussion-form discussion-form-container discussion-notes">
+    <div
+      v-if="glFeatures.multilineComments"
+      class="gl-mb-3 gl-text-gray-700 gl-border-gray-200 gl-border-b-solid gl-border-b-1 gl-pb-3"
+    >
+      <multiline-comment-form
+        v-model="commentLineStart"
+        :line="line"
+        :comment-line-options="commentLineOptions"
+      />
+    </div>
     <user-avatar-link
       v-if="author"
       :link-href="author.path"
@@ -133,7 +163,7 @@ export default {
       :diff-file="diffFile"
       :show-suggest-popover="showSuggestPopover"
       save-button-title="Comment"
-      class="diff-comment-form"
+      class="diff-comment-form prepend-top-10"
       @handleFormUpdateAddToReview="addToReview"
       @cancelForm="handleCancelCommentForm"
       @handleFormUpdate="handleSaveNote"
diff --git a/app/assets/javascripts/diffs/components/inline_diff_view.vue b/app/assets/javascripts/diffs/components/inline_diff_view.vue
index f1c42e7cc723f6..ad72016f03ba8e 100644
--- a/app/assets/javascripts/diffs/components/inline_diff_view.vue
+++ b/app/assets/javascripts/diffs/components/inline_diff_view.vue
@@ -80,6 +80,8 @@ export default {
           v-if="shouldRenderDraftRow(diffFile.file_hash, line)"
           :key="`draft_${index}`"
           :draft="draftForLine(diffFile.file_hash, line)"
+          :diff-file="diffFile"
+          :line="line"
         />
       </template>
     </tbody>
diff --git a/app/assets/javascripts/diffs/store/utils.js b/app/assets/javascripts/diffs/store/utils.js
index 2be71c770877f0..d261be1b550919 100644
--- a/app/assets/javascripts/diffs/store/utils.js
+++ b/app/assets/javascripts/diffs/store/utils.js
@@ -40,6 +40,7 @@ export function getFormData(params) {
     diffViewType,
     linePosition,
     positionType,
+    lineRange,
   } = params;
 
   const position = JSON.stringify({
@@ -55,6 +56,7 @@ export function getFormData(params) {
     y: params.y,
     width: params.width,
     height: params.height,
+    line_range: lineRange,
   });
 
   const postData = {
diff --git a/app/assets/javascripts/notes/components/multiline_comment_form.vue b/app/assets/javascripts/notes/components/multiline_comment_form.vue
new file mode 100644
index 00000000000000..5fba011a1535a9
--- /dev/null
+++ b/app/assets/javascripts/notes/components/multiline_comment_form.vue
@@ -0,0 +1,68 @@
+<script>
+import { GlFormSelect, GlSprintf } from '@gitlab/ui';
+import { getSymbol, getLineClasses } from './multiline_comment_utils';
+
+export default {
+  components: { GlFormSelect, GlSprintf },
+  props: {
+    lineRange: {
+      type: Object,
+      required: false,
+      default: null,
+    },
+    line: {
+      type: Object,
+      required: true,
+    },
+    commentLineOptions: {
+      type: Array,
+      required: true,
+    },
+  },
+  data() {
+    return {
+      commentLineStart: {
+        lineCode: this.lineRange ? this.lineRange.start_line_code : this.line.line_code,
+        type: this.lineRange ? this.lineRange.start_line_type : this.line.type,
+      },
+    };
+  },
+  methods: {
+    getSymbol({ type }) {
+      return getSymbol(type);
+    },
+    getLineClasses(line) {
+      return getLineClasses(line);
+    },
+  },
+};
+</script>
+
+<template>
+  <div>
+    <gl-sprintf
+      :message="
+        s__('MergeRequestDiffs|Commenting on lines %{selectStart}start%{selectEnd} to %{end}')
+      "
+    >
+      <template #select>
+        <label for="comment-line-start" class="sr-only">{{
+          s__('MergeRequestDiffs|Select comment starting line')
+        }}</label>
+        <gl-form-select
+          id="comment-line-start"
+          :value="commentLineStart"
+          :options="commentLineOptions"
+          size="sm"
+          class="gl-w-auto gl-vertical-align-baseline"
+          @change="$emit('input', $event)"
+        />
+      </template>
+      <template #end>
+        <span :class="getLineClasses(line)">
+          {{ getSymbol(line) + (line.new_line || line.old_line) }}
+        </span>
+      </template>
+    </gl-sprintf>
+  </div>
+</template>
diff --git a/app/assets/javascripts/notes/components/multiline_comment_utils.js b/app/assets/javascripts/notes/components/multiline_comment_utils.js
new file mode 100644
index 00000000000000..dc9c55e9b30f12
--- /dev/null
+++ b/app/assets/javascripts/notes/components/multiline_comment_utils.js
@@ -0,0 +1,57 @@
+import { takeRightWhile } from 'lodash';
+
+export function getSymbol(type) {
+  if (type === 'new') return '+';
+  if (type === 'old') return '-';
+  return '';
+}
+
+function getLineNumber(lineRange, key) {
+  if (!lineRange || !key) return '';
+  const lineCode = lineRange[`${key}_line_code`] || '';
+  const lineType = lineRange[`${key}_line_type`] || '';
+  const lines = lineCode.split('_') || [];
+  const lineNumber = lineType === 'old' ? lines[1] : lines[2];
+  return (lineNumber && getSymbol(lineType) + lineNumber) || '';
+}
+
+export function getStartLineNumber(lineRange) {
+  return getLineNumber(lineRange, 'start');
+}
+
+export function getEndLineNumber(lineRange) {
+  return getLineNumber(lineRange, 'end');
+}
+
+export function getLineClasses(line) {
+  const symbol = typeof line === 'string' ? line.charAt(0) : getSymbol(line?.type);
+
+  if (symbol !== '+' && symbol !== '-') return '';
+
+  return [
+    'gl-px-1 gl-rounded-small gl-border-solid gl-border-1 gl-border-white',
+    {
+      'gl-bg-green-100 gl-text-green-800': symbol === '+',
+      'gl-bg-red-100 gl-text-red-800': symbol === '-',
+    },
+  ];
+}
+
+export function commentLineOptions(diffLines, lineCode) {
+  const selectedIndex = diffLines.findIndex(line => line.line_code === lineCode);
+  const notMatchType = l => l.type !== 'match';
+
+  // We're limiting adding comments to only lines above the current line
+  // to make rendering simpler. Future interations will use a more
+  // intuitive dragging interface that will make this unnecessary
+  const upToSelected = diffLines.slice(0, selectedIndex + 1);
+
+  // Only include the lines up to the first "Show unchanged lines" block
+  // i.e. not a "match" type
+  const lines = takeRightWhile(upToSelected, notMatchType);
+
+  return lines.map(l => ({
+    value: { lineCode: l.line_code, type: l.type },
+    text: `${getSymbol(l.type)}${l.new_line || l.old_line}`,
+  }));
+}
diff --git a/app/assets/javascripts/notes/components/noteable_note.vue b/app/assets/javascripts/notes/components/noteable_note.vue
index 161bb4336ae81f..ada7c0465a01e7 100644
--- a/app/assets/javascripts/notes/components/noteable_note.vue
+++ b/app/assets/javascripts/notes/components/noteable_note.vue
@@ -2,6 +2,8 @@
 import $ from 'jquery';
 import { mapGetters, mapActions } from 'vuex';
 import { escape } from 'lodash';
+import { GlSprintf } from '@gitlab/ui';
+import glFeatureFlagsMixin from '~/vue_shared/mixins/gl_feature_flags_mixin';
 import { truncateSha } from '~/lib/utils/text_utility';
 import TimelineEntryItem from '~/vue_shared/components/notes/timeline_entry_item.vue';
 import { __, s__, sprintf } from '../../locale';
@@ -14,17 +16,26 @@ import eventHub from '../event_hub';
 import noteable from '../mixins/noteable';
 import resolvable from '../mixins/resolvable';
 import httpStatusCodes from '~/lib/utils/http_status';
+import {
+  getStartLineNumber,
+  getEndLineNumber,
+  getLineClasses,
+  commentLineOptions,
+} from './multiline_comment_utils';
+import MultilineCommentForm from './multiline_comment_form.vue';
 
 export default {
   name: 'NoteableNote',
   components: {
+    GlSprintf,
     userAvatarLink,
     noteHeader,
     noteActions,
     NoteBody,
     TimelineEntryItem,
+    MultilineCommentForm,
   },
-  mixins: [noteable, resolvable],
+  mixins: [noteable, resolvable, glFeatureFlagsMixin()],
   props: {
     note: {
       type: Object,
@@ -50,6 +61,11 @@ export default {
       required: false,
       default: false,
     },
+    diffLines: {
+      type: Object,
+      required: false,
+      default: null,
+    },
   },
   data() {
     return {
@@ -57,9 +73,14 @@ export default {
       isDeleting: false,
       isRequesting: false,
       isResolving: false,
+      commentLineStart: {
+        line_code: this.line?.line_code,
+        type: this.line?.type,
+      },
     };
   },
   computed: {
+    ...mapGetters('diffs', ['getDiffFileByHash']),
     ...mapGetters(['targetNoteHash', 'getNoteableData', 'getUserData', 'commentsDisabled']),
     author() {
       return this.note.author;
@@ -113,6 +134,32 @@ export default {
         (this.note.isDraft && this.note.discussion_id !== null)
       );
     },
+    lineRange() {
+      return this.note.position?.line_range;
+    },
+    startLineNumber() {
+      return getStartLineNumber(this.lineRange);
+    },
+    endLineNumber() {
+      return getEndLineNumber(this.lineRange);
+    },
+    showMultiLineComment() {
+      return (
+        this.glFeatures.multilineComments &&
+        this.startLineNumber &&
+        this.endLineNumber &&
+        (this.startLineNumber !== this.endLineNumber || this.isEditing)
+      );
+    },
+    commentLineOptions() {
+      if (this.diffLines) {
+        return commentLineOptions(this.diffLines, this.line.line_code);
+      }
+
+      const diffFile = this.diffFile || this.getDiffFileByHash(this.targetNoteHash);
+      if (!diffFile) return null;
+      return commentLineOptions(diffFile.highlighted_diff_lines, this.line.line_code);
+    },
   },
 
   created() {
@@ -174,10 +221,20 @@ export default {
       this.$emit('updateSuccess');
     },
     formUpdateHandler(noteText, parentElement, callback, resolveDiscussion) {
+      const position = {
+        ...this.note.position,
+        line_range: {
+          start_line_code: this.commentLineStart?.lineCode,
+          start_line_type: this.commentLineStart?.type,
+          end_line_code: this.line?.line_code,
+          end_line_type: this.line?.type,
+        },
+      };
       this.$emit('handleUpdateNote', {
         note: this.note,
         noteText,
         resolveDiscussion,
+        position,
         callback: () => this.updateSuccess(),
       });
 
@@ -239,6 +296,9 @@ export default {
         noteBody.note.note = noteText;
       }
     },
+    getLineClasses(lineNumber) {
+      return getLineClasses(lineNumber);
+    },
   },
 };
 </script>
@@ -251,6 +311,26 @@ export default {
     :data-note-id="note.id"
     class="note note-wrapper qa-noteable-note-item"
   >
+    <div v-if="showMultiLineComment" data-testid="multiline-comment">
+      <multiline-comment-form
+        v-if="isEditing && commentLineOptions && line"
+        v-model="commentLineStart"
+        :line="line"
+        :comment-line-options="commentLineOptions"
+        :line-range="note.position.line_range"
+        class="gl-mb-3 gl-text-gray-700 gl-border-gray-200 gl-border-b-solid gl-border-b-1 gl-pb-3"
+      />
+      <div v-else class="gl-mb-3 gl-text-gray-700">
+        <gl-sprintf :message="__('Comment on lines %{startLine} to %{endLine}')">
+          <template #startLine>
+            <span :class="getLineClasses(startLineNumber)">{{ startLineNumber }}</span>
+          </template>
+          <template #endLine>
+            <span :class="getLineClasses(endLineNumber)">{{ endLineNumber }}</span>
+          </template>
+        </gl-sprintf>
+      </div>
+    </div>
     <div v-once class="timeline-icon">
       <user-avatar-link
         :link-href="author.path"
diff --git a/app/controllers/projects/merge_requests_controller.rb b/app/controllers/projects/merge_requests_controller.rb
index 5613b5b9589a9e..4beba42dff0d2c 100644
--- a/app/controllers/projects/merge_requests_controller.rb
+++ b/app/controllers/projects/merge_requests_controller.rb
@@ -33,6 +33,7 @@ class Projects::MergeRequestsController < Projects::MergeRequests::ApplicationCo
     push_frontend_feature_flag(:widget_visibility_polling, @project, default_enabled: true)
     push_frontend_feature_flag(:merge_ref_head_comments, @project)
     push_frontend_feature_flag(:mr_commit_neighbor_nav, @project, default_enabled: true)
+    push_frontend_feature_flag(:multiline_comments, @project)
   end
 
   before_action do
diff --git a/changelogs/unreleased/jdb-mutliline-comment-fe.yml b/changelogs/unreleased/jdb-mutliline-comment-fe.yml
new file mode 100644
index 00000000000000..da4b6e28dd51c7
--- /dev/null
+++ b/changelogs/unreleased/jdb-mutliline-comment-fe.yml
@@ -0,0 +1,5 @@
+---
+title: Add frontend support for multiline comments
+merge_request: 29516
+author:
+type: added
diff --git a/doc/api/discussions.md b/doc/api/discussions.md
index 7235d342e64614..1f509a7aadca7d 100644
--- a/doc/api/discussions.md
+++ b/doc/api/discussions.md
@@ -783,7 +783,9 @@ Diff comments also contain position:
           "new_line": 27,
           "line_range": {
             "start_line_code": "588440f66559714280628a4f9799f0c4eb880a4a_10_10",
-            "end_line_code": "588440f66559714280628a4f9799f0c4eb880a4a_11_11"
+            "start_line_type": "new",
+            "end_line_code": "588440f66559714280628a4f9799f0c4eb880a4a_11_11",
+            "end_line_type": "old"
           }
         },
         "resolved": false,
@@ -848,6 +850,8 @@ Parameters:
 | `position[line_range]`                  | hash           | no       | Line range for a multi-line diff note |
 | `position[line_range][start_line_code]` | string         | yes      | Line code for the start line |
 | `position[line_range][end_line_code]`   | string         | yes      | Line code for the end line |
+| `position[line_range][start_line_type]` | string         | yes      | Line type for the start line |
+| `position[line_range][end_line_type]`   | string         | yes      | Line type for the end line |
 | `position[width]`                       | integer        | no       | Width of the image (for 'image' diff notes) |
 | `position[height]`                      | integer        | no       | Height of the image (for 'image' diff notes) |
 | `position[x]`                           | integer        | no       | X coordinate (for 'image' diff notes) |
diff --git a/lib/api/discussions.rb b/lib/api/discussions.rb
index 0dd1850e526b7b..7b453ada41c564 100644
--- a/lib/api/discussions.rb
+++ b/lib/api/discussions.rb
@@ -78,6 +78,8 @@ class Discussions < Grape::API
             optional :line_range, type: Hash, desc: 'Multi-line start and end' do
               requires :start_line_code, type: String, desc: 'Start line code for multi-line note'
               requires :end_line_code, type: String, desc: 'End line code for multi-line note'
+              requires :start_line_type, type: String, desc: 'Start line type for multi-line note'
+              requires :end_line_type, type: String, desc: 'End line type for multi-line note'
             end
           end
         end
diff --git a/locale/gitlab.pot b/locale/gitlab.pot
index d67394f99a4bcb..fe9bdf5716eb0c 100644
--- a/locale/gitlab.pot
+++ b/locale/gitlab.pot
@@ -830,6 +830,9 @@ msgstr ""
 msgid "8 hours"
 msgstr ""
 
+msgid ":%{startLine} to %{endLine}"
+msgstr ""
+
 msgid "< 1 hour"
 msgstr ""
 
@@ -5568,6 +5571,9 @@ msgstr ""
 msgid "Comment is being updated"
 msgstr ""
 
+msgid "Comment on lines %{startLine} to %{endLine}"
+msgstr ""
+
 msgid "Comment/Reply (quoting selected text)"
 msgstr ""
 
@@ -13609,6 +13615,12 @@ msgstr ""
 msgid "MergeConflict|origin//their changes"
 msgstr ""
 
+msgid "MergeRequestDiffs|Commenting on lines %{selectStart}start%{selectEnd} to %{end}"
+msgstr ""
+
+msgid "MergeRequestDiffs|Select comment starting line"
+msgstr ""
+
 msgid "MergeRequests|Add a reply"
 msgstr ""
 
diff --git a/spec/features/merge_request/user_comments_on_diff_spec.rb b/spec/features/merge_request/user_comments_on_diff_spec.rb
index 7d90fdaac16bee..bf7194be9c6853 100644
--- a/spec/features/merge_request/user_comments_on_diff_spec.rb
+++ b/spec/features/merge_request/user_comments_on_diff_spec.rb
@@ -114,6 +114,40 @@
     include_examples 'comment on merge request file'
   end
 
+  context 'when adding multiline comments' do
+    it 'saves a multiline comment' do
+      click_diff_line(find("[id='#{sample_commit.line_code}']"))
+
+      page.within('.discussion-form') do
+        find('#comment-line-start option', text: '-13').select_option
+      end
+
+      page.within('.js-discussion-note-form') do
+        fill_in(:note_note, with: 'Line is wrong')
+        click_button('Add comment now')
+      end
+
+      wait_for_requests
+
+      page.within('.notes_holder') do
+        expect(page).to have_content('Line is wrong')
+        expect(page).to have_content('Comment on lines -13 to +14')
+      end
+
+      visit(merge_request_path(merge_request))
+
+      page.within('.notes .discussion') do
+        expect(page).to have_content("#{user.name} #{user.to_reference} started a thread")
+        expect(page).to have_content(sample_commit.line_code_path)
+        expect(page).to have_content('Line is wrong')
+      end
+
+      page.within('.notes-tab .badge') do
+        expect(page).to have_content('1')
+      end
+    end
+  end
+
   context 'when editing comments' do
     it 'edits a comment' do
       click_diff_line(find("[id='#{sample_commit.line_code}']"))
diff --git a/spec/frontend/diffs/components/diff_line_note_form_spec.js b/spec/frontend/diffs/components/diff_line_note_form_spec.js
index 3e0acd0dace0c1..623df8bd55e010 100644
--- a/spec/frontend/diffs/components/diff_line_note_form_spec.js
+++ b/spec/frontend/diffs/components/diff_line_note_form_spec.js
@@ -77,12 +77,24 @@ describe('DiffLineNoteForm', () => {
           .spyOn(wrapper.vm, 'saveDiffDiscussion')
           .mockReturnValue(Promise.resolve());
 
+        const lineRange = {
+          start_line_code: wrapper.vm.commentLineStart.lineCode,
+          start_line_type: wrapper.vm.commentLineStart.type,
+          end_line_code: wrapper.vm.line.line_code,
+          end_line_type: wrapper.vm.line.type,
+        };
+
+        const formData = {
+          ...wrapper.vm.formData,
+          lineRange,
+        };
+
         wrapper.vm
           .handleSaveNote('note body')
           .then(() => {
             expect(saveDiffDiscussionSpy).toHaveBeenCalledWith({
               note: 'note body',
-              formData: wrapper.vm.formData,
+              formData,
             });
           })
           .then(done)
diff --git a/spec/frontend/diffs/store/actions_spec.js b/spec/frontend/diffs/store/actions_spec.js
index 86db6b3572fdb4..efc50597952be0 100644
--- a/spec/frontend/diffs/store/actions_spec.js
+++ b/spec/frontend/diffs/store/actions_spec.js
@@ -465,9 +465,9 @@ describe('DiffsStoreActions', () => {
                   new_path: 'file1',
                   old_line: 5,
                   old_path: 'file2',
+                  line_range: null,
                   line_code: 'ABC_1_1',
                   position_type: 'text',
-                  line_range: null,
                 },
               },
               hash: 'ABC_123',
diff --git a/spec/frontend/diffs/store/utils_spec.js b/spec/frontend/diffs/store/utils_spec.js
index 641373e666f629..296069afa2ca48 100644
--- a/spec/frontend/diffs/store/utils_spec.js
+++ b/spec/frontend/diffs/store/utils_spec.js
@@ -187,6 +187,7 @@ describe('DiffsStoreUtils', () => {
         },
         diffViewType: PARALLEL_DIFF_VIEW_TYPE,
         linePosition: LINE_POSITION_LEFT,
+        lineRange: { start_line_code: 'abc_1_1', end_line_code: 'abc_2_2' },
       };
 
       const position = JSON.stringify({
@@ -198,6 +199,7 @@ describe('DiffsStoreUtils', () => {
         position_type: TEXT_DIFF_POSITION_TYPE,
         old_line: options.noteTargetLine.old_line,
         new_line: options.noteTargetLine.new_line,
+        line_range: options.lineRange,
       });
 
       const postData = {
diff --git a/spec/frontend/notes/components/multiline_comment_utils_spec.js b/spec/frontend/notes/components/multiline_comment_utils_spec.js
new file mode 100644
index 00000000000000..261bfb106e7811
--- /dev/null
+++ b/spec/frontend/notes/components/multiline_comment_utils_spec.js
@@ -0,0 +1,49 @@
+import {
+  getSymbol,
+  getStartLineNumber,
+  getEndLineNumber,
+} from '~/notes/components/multiline_comment_utils';
+
+describe('Multiline comment utilities', () => {
+  describe('getStartLineNumber', () => {
+    it.each`
+      lineCode        | type     | result
+      ${'abcdef_1_1'} | ${'old'} | ${'-1'}
+      ${'abcdef_1_1'} | ${'new'} | ${'+1'}
+      ${'abcdef_1_1'} | ${null}  | ${'1'}
+      ${'abcdef'}     | ${'new'} | ${''}
+      ${'abcdef'}     | ${'old'} | ${''}
+      ${'abcdef'}     | ${null}  | ${''}
+    `('returns line number', ({ lineCode, type, result }) => {
+      expect(getStartLineNumber({ start_line_code: lineCode, start_line_type: type })).toEqual(
+        result,
+      );
+    });
+  });
+  describe('getEndLineNumber', () => {
+    it.each`
+      lineCode        | type     | result
+      ${'abcdef_1_1'} | ${'old'} | ${'-1'}
+      ${'abcdef_1_1'} | ${'new'} | ${'+1'}
+      ${'abcdef_1_1'} | ${null}  | ${'1'}
+      ${'abcdef'}     | ${'new'} | ${''}
+      ${'abcdef'}     | ${'old'} | ${''}
+      ${'abcdef'}     | ${null}  | ${''}
+    `('returns line number', ({ lineCode, type, result }) => {
+      expect(getEndLineNumber({ end_line_code: lineCode, end_line_type: type })).toEqual(result);
+    });
+  });
+  describe('getSymbol', () => {
+    it.each`
+      type         | result
+      ${'new'}     | ${'+'}
+      ${'old'}     | ${'-'}
+      ${'unused'}  | ${''}
+      ${''}        | ${''}
+      ${null}      | ${''}
+      ${undefined} | ${''}
+    `('`$type` returns `$result`', ({ type, result }) => {
+      expect(getSymbol(type)).toEqual(result);
+    });
+  });
+});
diff --git a/spec/frontend/notes/components/noteable_note_spec.js b/spec/frontend/notes/components/noteable_note_spec.js
index 0d67b1d87a9127..aa3eaa97e200c3 100644
--- a/spec/frontend/notes/components/noteable_note_spec.js
+++ b/spec/frontend/notes/components/noteable_note_spec.js
@@ -1,5 +1,5 @@
 import { escape } from 'lodash';
-import { shallowMount, createLocalVue } from '@vue/test-utils';
+import { mount, createLocalVue } from '@vue/test-utils';
 import createStore from '~/notes/stores';
 import issueNote from '~/notes/components/noteable_note.vue';
 import NoteHeader from '~/notes/components/note_header.vue';
@@ -8,9 +8,19 @@ import NoteActions from '~/notes/components/note_actions.vue';
 import NoteBody from '~/notes/components/note_body.vue';
 import { noteableDataMock, notesDataMock, note } from '../mock_data';
 
+jest.mock('~/vue_shared/mixins/gl_feature_flags_mixin', () => () => ({
+  inject: {
+    glFeatures: {
+      from: 'glFeatures',
+      default: () => ({ multilineComments: true }),
+    },
+  },
+}));
+
 describe('issue_note', () => {
   let store;
   let wrapper;
+  const findMultilineComment = () => wrapper.find('[data-testid="multiline-comment"]');
 
   beforeEach(() => {
     store = createStore();
@@ -18,12 +28,13 @@ describe('issue_note', () => {
     store.dispatch('setNotesData', notesDataMock);
 
     const localVue = createLocalVue();
-    wrapper = shallowMount(localVue.extend(issueNote), {
+    wrapper = mount(localVue.extend(issueNote), {
       store,
       propsData: {
         note,
       },
       localVue,
+      stubs: ['note-header', 'user-avatar-link', 'note-actions', 'note-body'],
     });
   });
 
@@ -31,6 +42,44 @@ describe('issue_note', () => {
     wrapper.destroy();
   });
 
+  describe('mutiline comments', () => {
+    it('should render if has multiline comment', () => {
+      const position = {
+        line_range: {
+          start_line_code: 'abc_1_1',
+          end_line_code: 'abc_2_2',
+        },
+      };
+      wrapper.setProps({
+        note: { ...note, position },
+      });
+
+      return wrapper.vm.$nextTick().then(() => {
+        expect(findMultilineComment().text()).toEqual('Comment on lines 1 to 2');
+      });
+    });
+
+    it('should not render if has single line comment', () => {
+      const position = {
+        line_range: {
+          start_line_code: 'abc_1_1',
+          end_line_code: 'abc_1_1',
+        },
+      };
+      wrapper.setProps({
+        note: { ...note, position },
+      });
+
+      return wrapper.vm.$nextTick().then(() => {
+        expect(findMultilineComment().exists()).toBe(false);
+      });
+    });
+
+    it('should not render if `line_range` is unavailable', () => {
+      expect(findMultilineComment().exists()).toBe(false);
+    });
+  });
+
   it('should render user information', () => {
     const { author } = note;
     const avatar = wrapper.find(UserAvatarLink);
diff --git a/spec/support/shared_examples/features/comments_on_merge_request_files_shared_examples.rb b/spec/support/shared_examples/features/comments_on_merge_request_files_shared_examples.rb
index 56206a421d6f56..e0a032b1a43d57 100644
--- a/spec/support/shared_examples/features/comments_on_merge_request_files_shared_examples.rb
+++ b/spec/support/shared_examples/features/comments_on_merge_request_files_shared_examples.rb
@@ -13,6 +13,7 @@
 
     page.within('.notes_holder') do
       expect(page).to have_content('Line is wrong')
+      expect(page).not_to have_content('Comment on lines')
     end
 
     visit(merge_request_path(merge_request))
diff --git a/spec/support/shared_examples/requests/api/diff_discussions_shared_examples.rb b/spec/support/shared_examples/requests/api/diff_discussions_shared_examples.rb
index 3d25b9076ad45f..518c5b8dc28ee3 100644
--- a/spec/support/shared_examples/requests/api/diff_discussions_shared_examples.rb
+++ b/spec/support/shared_examples/requests/api/diff_discussions_shared_examples.rb
@@ -30,7 +30,9 @@
     it "creates a new diff note" do
       line_range = {
         "start_line_code" => Gitlab::Git.diff_line_code(diff_note.position.file_path, 1, 1),
-        "end_line_code" => Gitlab::Git.diff_line_code(diff_note.position.file_path, 2, 2)
+        "end_line_code" => Gitlab::Git.diff_line_code(diff_note.position.file_path, 2, 2),
+        "start_line_type" => diff_note.position.type,
+        "end_line_type" => diff_note.position.type
       }
 
       position = diff_note.position.to_h.merge({ line_range: line_range })
-- 
GitLab