Allow suggesting single line changes in diffs

29 files changed, 656 insertions, 16 deletions

diff --git a/app/assets/javascripts/api.js b/app/assets/javascripts/api.js
index e2740981a4b..7607c4b3b79 100644
--- a/app/assets/javascripts/api.js
+++ b/app/assets/javascripts/api.js
@@ -25,6 +25,7 @@ const Api = {
   userStatusPath: '/api/:version/users/:id/status',
   userPostStatusPath: '/api/:version/user/status',
   commitPath: '/api/:version/projects/:id/repository/commits',
+  applySuggestionPath: '/api/:version/suggestions/:id/apply',
   commitPipelinesPath: '/:project_id/commit/:sha/pipelines',
   branchSinglePath: '/api/:version/projects/:id/repository/branches/:branch',
   createBranchPath: '/api/:version/projects/:id/repository/branches',
@@ -185,6 +186,12 @@ const Api = {
     });
   },
 
+  applySuggestion(id) {
+    const url = Api.buildUrl(Api.applySuggestionPath).replace(':id', encodeURIComponent(id));
+
+    return axios.put(url);
+  },
+
   commitPipelines(projectId, sha) {
     const encodedProjectId = projectId
       .split('/')
diff --git a/app/assets/javascripts/diffs/components/app.vue b/app/assets/javascripts/diffs/components/app.vue
index f0e82b1ed27..d4c1b07093d 100644
--- a/app/assets/javascripts/diffs/components/app.vue
+++ b/app/assets/javascripts/diffs/components/app.vue
@@ -42,6 +42,11 @@ export default {
       type: Object,
       required: true,
     },
+    helpPagePath: {
+      type: String,
+      required: false,
+      default: '',
+    },
     changesEmptyStateIllustration: {
       type: String,
       required: false,
@@ -208,6 +213,7 @@ export default {
               v-for="file in diffFiles"
               :key="file.newPath"
               :file="file"
+              :help-page-path="helpPagePath"
               :can-current-user-fork="canCurrentUserFork"
             />
           </template>
diff --git a/app/assets/javascripts/diffs/components/diff_content.vue b/app/assets/javascripts/diffs/components/diff_content.vue
index 11cc4c09fed..ac963f2971e 100644
--- a/app/assets/javascripts/diffs/components/diff_content.vue
+++ b/app/assets/javascripts/diffs/components/diff_content.vue
@@ -23,6 +23,11 @@ export default {
       type: Object,
       required: true,
     },
+    helpPagePath: {
+      type: String,
+      required: false,
+      default: '',
+    },
   },
   computed: {
     ...mapState({
@@ -74,11 +79,13 @@ export default {
           v-if="isInlineView"
           :diff-file="diffFile"
           :diff-lines="diffFile.highlighted_diff_lines || []"
+          :help-page-path="helpPagePath"
         />
         <parallel-diff-view
           v-if="isParallelView"
           :diff-file="diffFile"
           :diff-lines="diffFile.parallel_diff_lines || []"
+          :help-page-path="helpPagePath"
         />
       </template>
       <diff-viewer
diff --git a/app/assets/javascripts/diffs/components/diff_discussions.vue b/app/assets/javascripts/diffs/components/diff_discussions.vue
index bee29b04e92..b2021cd6061 100644
--- a/app/assets/javascripts/diffs/components/diff_discussions.vue
+++ b/app/assets/javascripts/diffs/components/diff_discussions.vue
@@ -13,6 +13,11 @@ export default {
       type: Array,
       required: true,
     },
+    line: {
+      type: Object,
+      required: false,
+      default: null,
+    },
     shouldCollapseDiscussions: {
       type: Boolean,
       required: false,
@@ -23,6 +28,11 @@ export default {
       required: false,
       default: false,
     },
+    helpPagePath: {
+      type: String,
+      required: false,
+      default: '',
+    },
   },
   methods: {
     ...mapActions(['toggleDiscussion']),
@@ -72,6 +82,8 @@ export default {
           :render-diff-file="false"
           :always-expanded="true"
           :discussions-by-diff-order="true"
+          :line="line"
+          :help-page-path="helpPagePath"
           @noteDeleted="deleteNoteHandler"
         >
           <span v-if="renderAvatarBadge" slot="avatar-badge" class="badge badge-pill">
diff --git a/app/assets/javascripts/diffs/components/diff_file.vue b/app/assets/javascripts/diffs/components/diff_file.vue
index bed29efb253..449f7007077 100644
--- a/app/assets/javascripts/diffs/components/diff_file.vue
+++ b/app/assets/javascripts/diffs/components/diff_file.vue
@@ -23,6 +23,11 @@ export default {
       type: Boolean,
       required: true,
     },
+    helpPagePath: {
+      type: String,
+      required: false,
+      default: '',
+    },
   },
   data() {
     return {
@@ -164,6 +169,7 @@ export default {
       v-if="!isCollapsed && file.renderIt"
       :class="{ hidden: isCollapsed || file.too_large }"
       :diff-file="file"
+      :help-page-path="helpPagePath"
     />
     <gl-loading-icon v-if="showLoadingIcon" class="diff-content loading" />
     <div v-else-if="showExpandMessage" class="nothing-here-block diff-collapsed">
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 9fd02acbd6e..e7569ba7b84 100644
--- a/app/assets/javascripts/diffs/components/diff_line_note_form.vue
+++ b/app/assets/javascripts/diffs/components/diff_line_note_form.vue
@@ -94,6 +94,7 @@ export default {
       ref="noteForm"
       :is-editing="true"
       :line-code="line.line_code"
+      :line="line"
       save-button-title="Comment"
       class="diff-comment-form"
       @cancelForm="handleCancelCommentForm"
diff --git a/app/assets/javascripts/diffs/components/inline_diff_comment_row.vue b/app/assets/javascripts/diffs/components/inline_diff_comment_row.vue
index aa40b24950a..814ee0b7c02 100644
--- a/app/assets/javascripts/diffs/components/inline_diff_comment_row.vue
+++ b/app/assets/javascripts/diffs/components/inline_diff_comment_row.vue
@@ -16,6 +16,11 @@ export default {
       type: String,
       required: true,
     },
+    helpPagePath: {
+      type: String,
+      required: false,
+      default: '',
+    },
   },
   computed: {
     className() {
@@ -38,7 +43,12 @@ export default {
   <tr v-if="shouldRender" :class="className" class="notes_holder">
     <td class="notes_content" colspan="3">
       <div class="content">
-        <diff-discussions v-if="line.discussions.length" :discussions="line.discussions" />
+        <diff-discussions
+          v-if="line.discussions.length"
+          :line="line"
+          :discussions="line.discussions"
+          :help-page-path="helpPagePath"
+        />
         <diff-line-note-form
           v-if="line.hasForm"
           :diff-file-hash="diffFileHash"
diff --git a/app/assets/javascripts/diffs/components/inline_diff_view.vue b/app/assets/javascripts/diffs/components/inline_diff_view.vue
index 6a0ce760e6d..9310e2b7ca9 100644
--- a/app/assets/javascripts/diffs/components/inline_diff_view.vue
+++ b/app/assets/javascripts/diffs/components/inline_diff_view.vue
@@ -17,6 +17,11 @@ export default {
       type: Array,
       required: true,
     },
+    helpPagePath: {
+      type: String,
+      required: false,
+      default: '',
+    },
   },
   computed: {
     ...mapGetters('diffs', ['commitId']),
@@ -47,6 +52,7 @@ export default {
           :key="`icr-${index}`"
           :diff-file-hash="diffFile.file_hash"
           :line="line"
+          :help-page-path="helpPagePath"
         />
       </template>
     </tbody>
diff --git a/app/assets/javascripts/diffs/components/parallel_diff_comment_row.vue b/app/assets/javascripts/diffs/components/parallel_diff_comment_row.vue
index b98463d3dd3..a65cf025cde 100644
--- a/app/assets/javascripts/diffs/components/parallel_diff_comment_row.vue
+++ b/app/assets/javascripts/diffs/components/parallel_diff_comment_row.vue
@@ -20,6 +20,11 @@ export default {
       type: Number,
       required: true,
     },
+    helpPagePath: {
+      type: String,
+      required: false,
+      default: '',
+    },
   },
   computed: {
     hasExpandedDiscussionOnLeft() {
@@ -87,6 +92,8 @@ export default {
         <diff-discussions
           v-if="line.left.discussions.length"
           :discussions="line.left.discussions"
+          :line="line.left"
+          :help-page-path="helpPagePath"
         />
       </div>
       <diff-line-note-form
@@ -102,6 +109,8 @@ export default {
         <diff-discussions
           v-if="line.right.discussions.length"
           :discussions="line.right.discussions"
+          :line="line.right"
+          :help-page-path="helpPagePath"
         />
       </div>
       <diff-line-note-form
diff --git a/app/assets/javascripts/diffs/components/parallel_diff_view.vue b/app/assets/javascripts/diffs/components/parallel_diff_view.vue
index 9a6e0e82529..e6bc0daebb3 100644
--- a/app/assets/javascripts/diffs/components/parallel_diff_view.vue
+++ b/app/assets/javascripts/diffs/components/parallel_diff_view.vue
@@ -17,6 +17,11 @@ export default {
       type: Array,
       required: true,
     },
+    helpPagePath: {
+      type: String,
+      required: false,
+      default: '',
+    },
   },
   computed: {
     ...mapGetters('diffs', ['commitId']),
@@ -49,6 +54,7 @@ export default {
             :line="line"
             :diff-file-hash="diffFile.file_hash"
             :line-index="index"
+            :help-page-path="helpPagePath"
           />
         </template>
       </tbody>
diff --git a/app/assets/javascripts/diffs/index.js b/app/assets/javascripts/diffs/index.js
index 915cacb374f..b130cedc24c 100644
--- a/app/assets/javascripts/diffs/index.js
+++ b/app/assets/javascripts/diffs/index.js
@@ -16,6 +16,7 @@ export default function initDiffsApp(store) {
       return {
         endpoint: dataset.endpoint,
         projectPath: dataset.projectPath,
+        helpPagePath: dataset.helpPagePath,
         currentUser: JSON.parse(dataset.currentUserData) || {},
         changesEmptyStateIllustration: dataset.changesEmptyStateIllustration,
       };
@@ -31,6 +32,7 @@ export default function initDiffsApp(store) {
           endpoint: this.endpoint,
           currentUser: this.currentUser,
           projectPath: this.projectPath,
+          helpPagePath: this.helpPagePath,
           shouldShow: this.activeTab === 'diffs',
           changesEmptyStateIllustration: this.changesEmptyStateIllustration,
         },
diff --git a/app/assets/javascripts/lib/utils/text_markdown.js b/app/assets/javascripts/lib/utils/text_markdown.js
index 3618c6af7e2..c095a017866 100644
--- a/app/assets/javascripts/lib/utils/text_markdown.js
+++ b/app/assets/javascripts/lib/utils/text_markdown.js
@@ -39,7 +39,14 @@ function blockTagText(text, textArea, blockTag, selected) {
   }
 }
 
-function moveCursor({ textArea, tag, positionBetweenTags, removedLastNewLine, select }) {
+function moveCursor({
+  textArea,
+  tag,
+  cursorOffset,
+  positionBetweenTags,
+  removedLastNewLine,
+  select,
+}) {
   var pos;
   if (!textArea.setSelectionRange) {
     return;
@@ -61,11 +68,24 @@ function moveCursor({ textArea, tag, positionBetweenTags, removedLastNewLine, se
       pos -= 1;
     }
 
+    if (cursorOffset) {
+      pos -= cursorOffset;
+    }
+
     return textArea.setSelectionRange(pos, pos);
   }
 }
 
-export function insertMarkdownText({ textArea, text, tag, blockTag, selected, wrap, select }) {
+export function insertMarkdownText({
+  textArea,
+  text,
+  tag,
+  cursorOffset,
+  blockTag,
+  selected,
+  wrap,
+  select,
+}) {
   var textToInsert,
     selectedSplit,
     startChar,
@@ -154,20 +174,30 @@ export function insertMarkdownText({ textArea, text, tag, blockTag, selected, wr
   return moveCursor({
     textArea,
     tag: tag.replace(textPlaceholder, selected),
+    cursorOffset,
     positionBetweenTags: wrap && selected.length === 0,
     removedLastNewLine,
     select,
   });
 }
 
-function updateText({ textArea, tag, blockTag, wrap, select }) {
+function updateText({ textArea, tag, cursorOffset, blockTag, wrap, select, tagContent }) {
   var $textArea, selected, text;
   $textArea = $(textArea);
   textArea = $textArea.get(0);
   text = $textArea.val();
-  selected = selectedText(text, textArea);
+  selected = selectedText(text, textArea) || tagContent;
   $textArea.focus();
-  return insertMarkdownText({ textArea, text, tag, blockTag, selected, wrap, select });
+  return insertMarkdownText({
+    textArea,
+    text,
+    tag,
+    cursorOffset,
+    blockTag,
+    selected,
+    wrap,
+    select,
+  });
 }
 
 export function addMarkdownListeners(form) {
@@ -178,9 +208,11 @@ export function addMarkdownListeners(form) {
       return updateText({
         textArea: $this.closest('.md-area').find('textarea'),
         tag: $this.data('mdTag'),
+        cursorOffset: $this.data('mdCursorOffset'),
         blockTag: $this.data('mdBlock'),
         wrap: !$this.data('mdPrepend'),
         select: $this.data('mdSelect'),
+        tagContent: $this.data('mdTagContent').toString(),
       });
     });
 }
diff --git a/app/assets/javascripts/mr_notes/index.js b/app/assets/javascripts/mr_notes/index.js
index 1c98683c597..e4d72eb8318 100644
--- a/app/assets/javascripts/mr_notes/index.js
+++ b/app/assets/javascripts/mr_notes/index.js
@@ -33,6 +33,7 @@ export default function initMrNotes() {
         noteableData,
         currentUserData: JSON.parse(notesDataset.currentUserData),
         notesData: JSON.parse(notesDataset.notesData),
+        helpPagePath: notesDataset.helpPagePath,
       };
     },
     computed: {
@@ -71,6 +72,7 @@ export default function initMrNotes() {
           notesData: this.notesData,
           userData: this.currentUserData,
           shouldShow: this.activeTab === 'show',
+          helpPagePath: this.helpPagePath,
         },
       });
     },
diff --git a/app/assets/javascripts/notes/components/note_body.vue b/app/assets/javascripts/notes/components/note_body.vue
index c0bee600181..bcf5d334da4 100644
--- a/app/assets/javascripts/notes/components/note_body.vue
+++ b/app/assets/javascripts/notes/components/note_body.vue
@@ -1,10 +1,12 @@
 <script>
+import { mapActions } from 'vuex';
 import $ from 'jquery';
 import noteEditedText from './note_edited_text.vue';
 import noteAwardsList from './note_awards_list.vue';
 import noteAttachment from './note_attachment.vue';
 import noteForm from './note_form.vue';
 import autosave from '../mixins/autosave';
+import Suggestions from '~/vue_shared/components/markdown/suggestions.vue';
 
 export default {
   components: {
@@ -12,6 +14,7 @@ export default {
     noteAwardsList,
     noteAttachment,
     noteForm,
+    Suggestions,
   },
   mixins: [autosave],
   props: {
@@ -19,6 +22,11 @@ export default {
       type: Object,
       required: true,
     },
+    line: {
+      type: Object,
+      required: false,
+      default: null,
+    },
     canEdit: {
       type: Boolean,
       required: true,
@@ -28,11 +36,22 @@ export default {
       required: false,
       default: false,
     },
+    helpPagePath: {
+      type: String,
+      required: false,
+      default: '',
+    },
   },
   computed: {
     noteBody() {
       return this.note.note;
     },
+    hasSuggestion() {
+      return this.note.suggestions && this.note.suggestions.length;
+    },
+    lineType() {
+      return this.line ? this.line.type : null;
+    },
   },
   mounted() {
     this.renderGFM();
@@ -53,6 +72,7 @@ export default {
     }
   },
   methods: {
+    ...mapActions(['submitSuggestion']),
     renderGFM() {
       $(this.$refs['note-body']).renderGFM();
     },
@@ -62,19 +82,35 @@ export default {
     formCancelHandler(shouldConfirm, isDirty) {
       this.$emit('cancelForm', shouldConfirm, isDirty);
     },
+    applySuggestion({ suggestionId, flashContainer, callback }) {
+      const { discussion_id: discussionId, id: noteId } = this.note;
+
+      this.submitSuggestion({ discussionId, noteId, suggestionId, flashContainer, callback });
+    },
   },
 };
 </script>
 
 <template>
   <div ref="note-body" :class="{ 'js-task-list-container': canEdit }" class="note-body">
-    <div class="note-text md" v-html="note.note_html"></div>
+    <suggestions
+      v-if="hasSuggestion && !isEditing"
+      :suggestions="note.suggestions"
+      :note-html="note.note_html"
+      :line-type="lineType"
+      :help-page-path="helpPagePath"
+      @apply="applySuggestion"
+    />
+    <div v-else class="note-text md" v-html="note.note_html"></div>
     <note-form
       v-if="isEditing"
       ref="noteForm"
       :is-editing="isEditing"
       :note-body="noteBody"
       :note-id="note.id"
+      :line="line"
+      :note="note"
+      :help-page-path="helpPagePath"
       :markdown-version="note.cached_markdown_version"
       @handleFormUpdate="handleFormUpdate"
       @cancelForm="formCancelHandler"
diff --git a/app/assets/javascripts/notes/components/note_form.vue b/app/assets/javascripts/notes/components/note_form.vue
index 95164183ccb..9b7f3d3588d 100644
--- a/app/assets/javascripts/notes/components/note_form.vue
+++ b/app/assets/javascripts/notes/components/note_form.vue
@@ -1,4 +1,5 @@
 <script>
+import { mergeUrlParams } from '~/lib/utils/url_utility';
 import { mapGetters, mapActions } from 'vuex';
 import eventHub from '../event_hub';
 import issueWarning from '../../vue_shared/components/issue/issue_warning.vue';
@@ -53,6 +54,21 @@ export default {
       required: false,
       default: false,
     },
+    line: {
+      type: Object,
+      required: false,
+      default: null,
+    },
+    note: {
+      type: Object,
+      required: false,
+      default: null,
+    },
+    helpPagePath: {
+      type: String,
+      required: false,
+      default: '',
+    },
   },
   data() {
     return {
@@ -79,7 +95,8 @@ export default {
       return '#';
     },
     markdownPreviewPath() {
-      return this.getNoteableDataByProp('preview_note_path');
+      const notable = this.getNoteableDataByProp('preview_note_path');
+      return mergeUrlParams({ preview_suggestions: true }, notable);
     },
     markdownDocsPath() {
       return this.getNotesDataByProp('markdownDocsPath');
@@ -93,6 +110,18 @@ export default {
     isDisabled() {
       return !this.updatedNoteBody.length || this.isSubmitting;
     },
+    discussionNote() {
+      const discussionNote = this.discussion.id
+        ? this.getDiscussionLastNote(this.discussion)
+        : this.note;
+      return discussionNote || {};
+    },
+    canSuggest() {
+      return (
+        this.getNoteableData.can_receive_suggestion &&
+        (this.line && this.line.can_receive_suggestion)
+      );
+    },
   },
   watch: {
     noteBody() {
@@ -171,7 +200,11 @@ export default {
         :markdown-docs-path="markdownDocsPath"
         :markdown-version="markdownVersion"
         :quick-actions-docs-path="quickActionsDocsPath"
+        :line="line"
+        :note="discussionNote"
+        :can-suggest="canSuggest"
         :add-spacing-classes="false"
+        :help-page-path="helpPagePath"
       >
         <textarea
           id="note_note"
diff --git a/app/assets/javascripts/notes/components/noteable_discussion.vue b/app/assets/javascripts/notes/components/noteable_discussion.vue
index 5c9a28b8512..4156fe0d229 100644
--- a/app/assets/javascripts/notes/components/noteable_discussion.vue
+++ b/app/assets/javascripts/notes/components/noteable_discussion.vue
@@ -49,6 +49,11 @@ export default {
       type: Object,
       required: true,
     },
+    line: {
+      type: Object,
+      required: false,
+      default: null,
+    },
     renderDiffFile: {
       type: Boolean,
       required: false,
@@ -64,6 +69,11 @@ export default {
       required: false,
       default: false,
     },
+    helpPagePath: {
+      type: String,
+      required: false,
+      default: '',
+    },
   },
   data() {
     const { diff_discussion: isDiffDiscussion, resolved } = this.discussion;
@@ -194,6 +204,13 @@ export default {
         false,
       );
     },
+    diffLine() {
+      if (this.discussion.diff_discussion && this.discussion.truncated_diff_lines) {
+        return this.discussion.truncated_diff_lines.slice(-1)[0];
+      }
+
+      return this.line;
+    },
   },
   watch: {
     isReplying() {
@@ -357,6 +374,8 @@ Please check your network connection and try again.`;
                   <component
                     :is="componentName(initialDiscussion)"
                     :note="componentData(initialDiscussion)"
+                    :line="line"
+                    :help-page-path="helpPagePath"
                     @handleDeleteNote="deleteNoteHandler"
                   >
                     <slot slot="avatar-badge" name="avatar-badge"></slot>
@@ -373,6 +392,8 @@ Please check your network connection and try again.`;
                       v-for="note in replies"
                       :key="note.id"
                       :note="componentData(note)"
+                      :help-page-path="helpPagePath"
+                      :line="line"
                       @handleDeleteNote="deleteNoteHandler"
                     />
                   </template>
@@ -383,6 +404,8 @@ Please check your network connection and try again.`;
                     v-for="(note, index) in discussion.notes"
                     :key="note.id"
                     :note="componentData(note)"
+                    :help-page-path="helpPagePath"
+                    :line="diffLine"
                     @handleDeleteNote="deleteNoteHandler"
                   >
                     <slot v-if="index === 0" slot="avatar-badge" name="avatar-badge"></slot>
@@ -447,6 +470,7 @@ Please check your network connection and try again.`;
                   ref="noteForm"
                   :discussion="discussion"
                   :is-editing="false"
+                  :line="diffLine"
                   save-button-title="Comment"
                   @handleFormUpdate="saveReply"
                   @cancelForm="cancelReplyForm"
diff --git a/app/assets/javascripts/notes/components/noteable_note.vue b/app/assets/javascripts/notes/components/noteable_note.vue
index a17be51353e..57e9c40bd61 100644
--- a/app/assets/javascripts/notes/components/noteable_note.vue
+++ b/app/assets/javascripts/notes/components/noteable_note.vue
@@ -27,6 +27,16 @@ export default {
       type: Object,
       required: true,
     },
+    line: {
+      type: Object,
+      required: false,
+      default: null,
+    },
+    helpPagePath: {
+      type: String,
+      required: false,
+      default: '',
+    },
   },
   data() {
     return {
@@ -220,8 +230,10 @@ export default {
       <note-body
         ref="noteBody"
         :note="note"
+        :line="line"
         :can-edit="note.current_user.can_edit"
         :is-editing="isEditing"
+        :help-page-path="helpPagePath"
         @handleFormUpdate="formUpdateHandler"
         @cancelForm="formCancelHandler"
       />
diff --git a/app/assets/javascripts/notes/components/notes_app.vue b/app/assets/javascripts/notes/components/notes_app.vue
index 27f896cee35..f3fcfdfda05 100644
--- a/app/assets/javascripts/notes/components/notes_app.vue
+++ b/app/assets/javascripts/notes/components/notes_app.vue
@@ -49,6 +49,11 @@ export default {
       required: false,
       default: 0,
     },
+    helpPagePath: {
+      type: String,
+      required: false,
+      default: '',
+    },
   },
   data() {
     return {
@@ -206,6 +211,7 @@ export default {
           :key="discussion.id"
           :discussion="discussion"
           :render-diff-file="true"
+          :help-page-path="helpPagePath"
         />
       </template>
     </ul>
diff --git a/app/assets/javascripts/notes/services/notes_service.js b/app/assets/javascripts/notes/services/notes_service.js
index 47a6f07cce2..237e70c0a4c 100644
--- a/app/assets/javascripts/notes/services/notes_service.js
+++ b/app/assets/javascripts/notes/services/notes_service.js
@@ -1,4 +1,5 @@
 import Vue from 'vue';
+import Api from '~/api';
 import VueResource from 'vue-resource';
 import * as constants from '../constants';
 
@@ -44,4 +45,7 @@ export default {
   toggleIssueState(endpoint, data) {
     return Vue.http.put(endpoint, data);
   },
+  applySuggestion(id) {
+    return Api.applySuggestion(id);
+  },
 };
diff --git a/app/assets/javascripts/notes/stores/actions.js b/app/assets/javascripts/notes/stores/actions.js
index 4716ab52333..65f85314fa0 100644
--- a/app/assets/javascripts/notes/stores/actions.js
+++ b/app/assets/javascripts/notes/stores/actions.js
@@ -405,5 +405,25 @@ export const startTaskList = ({ dispatch }) =>
 export const updateResolvableDiscussonsCounts = ({ commit }) =>
   commit(types.UPDATE_RESOLVABLE_DISCUSSIONS_COUNTS);
 
+export const submitSuggestion = (
+  { commit },
+  { discussionId, noteId, suggestionId, flashContainer, callback },
+) => {
+  service
+    .applySuggestion(suggestionId)
+    .then(() => {
+      commit(types.APPLY_SUGGESTION, { discussionId, noteId, suggestionId });
+      callback();
+    })
+    .catch(() => {
+      Flash(
+        __('Something went wrong while applying the suggestion. Please try again.'),
+        'alert',
+        flashContainer,
+      );
+      callback();
+    });
+};
+
 // prevent babel-plugin-rewire from generating an invalid default during karma tests
 export default () => {};
diff --git a/app/assets/javascripts/notes/stores/modules/index.js b/app/assets/javascripts/notes/stores/modules/index.js
index b5fe8bdb1d3..887e6d22b06 100644
--- a/app/assets/javascripts/notes/stores/modules/index.js
+++ b/app/assets/javascripts/notes/stores/modules/index.js
@@ -20,6 +20,7 @@ export default () => ({
     userData: {},
     noteableData: {
       current_user: {},
+      preview_note_path: 'path/to/preview',
     },
     commentsDisabled: false,
     resolvableDiscussionsCount: 0,
diff --git a/app/assets/javascripts/notes/stores/mutation_types.js b/app/assets/javascripts/notes/stores/mutation_types.js
index 9c68ab67a8c..df943c155f4 100644
--- a/app/assets/javascripts/notes/stores/mutation_types.js
+++ b/app/assets/javascripts/notes/stores/mutation_types.js
@@ -16,6 +16,7 @@ export const SET_DISCUSSION_DIFF_LINES = 'SET_DISCUSSION_DIFF_LINES';
 export const SET_NOTES_FETCHED_STATE = 'SET_NOTES_FETCHED_STATE';
 export const SET_NOTES_LOADING_STATE = 'SET_NOTES_LOADING_STATE';
 export const DISABLE_COMMENTS = 'DISABLE_COMMENTS';
+export const APPLY_SUGGESTION = 'APPLY_SUGGESTION';
 
 // DISCUSSION
 export const COLLAPSE_DISCUSSION = 'COLLAPSE_DISCUSSION';
diff --git a/app/assets/javascripts/notes/stores/mutations.js b/app/assets/javascripts/notes/stores/mutations.js
index 39ff0ff73d7..8992454be2e 100644
--- a/app/assets/javascripts/notes/stores/mutations.js
+++ b/app/assets/javascripts/notes/stores/mutations.js
@@ -197,6 +197,17 @@ export default {
     }
   },
 
+  [types.APPLY_SUGGESTION](state, { noteId, discussionId, suggestionId }) {
+    const noteObj = utils.findNoteObjectById(state.discussions, discussionId);
+    const comment = utils.findNoteObjectById(noteObj.notes, noteId);
+
+    comment.suggestions = comment.suggestions.map(suggestion => ({
+      ...suggestion,
+      applied: suggestion.applied || suggestion.id === suggestionId,
+      appliable: false,
+    }));
+  },
+
   [types.UPDATE_DISCUSSION](state, noteData) {
     const note = noteData;
     const selectedDiscussion = state.discussions.find(disc => disc.id === note.id);
diff --git a/app/assets/javascripts/vue_shared/components/markdown/field.vue b/app/assets/javascripts/vue_shared/components/markdown/field.vue
index 43def2673eb..2f7ed4a982c 100644
--- a/app/assets/javascripts/vue_shared/components/markdown/field.vue
+++ b/app/assets/javascripts/vue_shared/components/markdown/field.vue
@@ -1,17 +1,21 @@
 <script>
 import $ from 'jquery';
+import _ from 'underscore';
 import { __ } from '~/locale';
+import { stripHtml } from '~/lib/utils/text_utility';
 import Flash from '../../../flash';
 import GLForm from '../../../gl_form';
 import markdownHeader from './header.vue';
 import markdownToolbar from './toolbar.vue';
 import icon from '../icon.vue';
+import Suggestions from '~/vue_shared/components/markdown/suggestions.vue';
 
 export default {
   components: {
     markdownHeader,
     markdownToolbar,
     icon,
+    Suggestions,
   },
   props: {
     markdownPreviewPath: {
@@ -48,12 +52,33 @@ export default {
       required: false,
       default: true,
     },
+    line: {
+      type: Object,
+      required: false,
+      default: null,
+    },
+    note: {
+      type: Object,
+      required: false,
+      default: () => ({}),
+    },
+    canSuggest: {
+      type: Boolean,
+      required: false,
+      default: false,
+    },
+    helpPagePath: {
+      type: String,
+      required: false,
+      default: '',
+    },
   },
   data() {
     return {
       markdownPreview: '',
       referencedCommands: '',
       referencedUsers: '',
+      hasSuggestion: false,
       markdownPreviewLoading: false,
       previewMarkdown: false,
     };
@@ -63,6 +88,39 @@ export default {
       const referencedUsersThreshold = 10;
       return this.referencedUsers.length >= referencedUsersThreshold;
     },
+    lineContent() {
+      const FIRST_CHAR_REGEX = /^(\+|-)/;
+      const [firstSuggestion] = this.suggestions;
+      if (firstSuggestion) {
+        return firstSuggestion.from_content;
+      }
+
+      if (this.line) {
+        const { rich_text: richText, text } = this.line;
+
+        if (text) {
+          return text.replace(FIRST_CHAR_REGEX, '');
+        }
+
+        return _.unescape(stripHtml(richText).replace(/\n/g, ''));
+      }
+
+      return '';
+    },
+    lineNumber() {
+      let lineNumber;
+      if (this.line) {
+        const { new_line: newLine, old_line: oldLine } = this.line;
+        lineNumber = newLine || oldLine;
+      }
+      return lineNumber;
+    },
+    suggestions() {
+      return this.note.suggestions || [];
+    },
+    lineType() {
+      return this.line ? this.line.type : '';
+    },
   },
   mounted() {
     /*
@@ -122,6 +180,7 @@ export default {
       if (data.references) {
         this.referencedCommands = data.references.commands;
         this.referencedUsers = data.references.users;
+        this.hasSuggestion = data.references.suggestions && data.references.suggestions.length;
       }
 
       this.$nextTick(() => {
@@ -147,6 +206,8 @@ export default {
   >
     <markdown-header
       :preview-markdown="previewMarkdown"
+      :line-content="lineContent"
+      :can-suggest="canSuggest"
       @preview-markdown="showPreviewTab"
       @write-markdown="showWriteTab"
     />
@@ -163,19 +224,39 @@ export default {
         />
       </div>
     </div>
-    <div
-      v-show="previewMarkdown"
-      ref="markdown-preview"
-      class="md-preview js-vue-md-preview md md-preview-holder"
-      v-html="markdownPreview"
-    ></div>
+    <template v-if="hasSuggestion">
+      <div
+        v-show="previewMarkdown"
+        ref="markdown-preview"
+        class="md-preview js-vue-md-preview md md-preview-holder"
+      >
+        <suggestions
+          v-if="hasSuggestion"
+          :note-html="markdownPreview"
+          :from-line="lineNumber"
+          :from-content="lineContent"
+          :line-type="lineType"
+          :disabled="true"
+          :suggestions="suggestions"
+          :help-page-path="helpPagePath"
+        />
+      </div>
+    </template>
+    <template v-else>
+      <div
+        v-show="previewMarkdown"
+        ref="markdown-preview"
+        class="md-preview js-vue-md-preview md md-preview-holder"
+        v-html="markdownPreview"
+      ></div>
+    </template>
     <template v-if="previewMarkdown && !markdownPreviewLoading">
       <div v-if="referencedCommands" class="referenced-commands" v-html="referencedCommands"></div>
       <div v-if="shouldShowReferencedUsers" class="referenced-users">
         <span>
-          <i class="fa fa-exclamation-triangle" aria-hidden="true"> </i> You are about to add
+          <i class="fa fa-exclamation-triangle" aria-hidden="true"></i> You are about to add
           <strong>
-            <span class="js-referenced-users-count"> {{ referencedUsers.length }} </span>
+            <span class="js-referenced-users-count">{{ referencedUsers.length }}</span>
           </strong>
           people to the discussion. Proceed with caution.
         </span>
diff --git a/app/assets/javascripts/vue_shared/components/markdown/header.vue b/app/assets/javascripts/vue_shared/components/markdown/header.vue
index 4c4ba537065..bf4d42670ee 100644
--- a/app/assets/javascripts/vue_shared/components/markdown/header.vue
+++ b/app/assets/javascripts/vue_shared/components/markdown/header.vue
@@ -17,6 +17,16 @@ export default {
       type: Boolean,
       required: true,
     },
+    lineContent: {
+      type: String,
+      required: false,
+      default: '',
+    },
+    canSuggest: {
+      type: Boolean,
+      required: false,
+      default: true,
+    },
   },
   computed: {
     mdTable() {
@@ -27,6 +37,9 @@ export default {
         '| cell | cell |',
       ].join('\n');
     },
+    mdSuggestion() {
+      return ['```suggestion', `{text}`, '```'].join('\n');
+    },
   },
   mounted() {
     $(document).on('markdown-preview:show.vue', this.previewMarkdownTab);
@@ -119,6 +132,16 @@ export default {
           :button-title="__('Add a table')"
           icon="table"
         />
+        <toolbar-button
+          v-if="canSuggest"
+          :tag="mdSuggestion"
+          :prepend="true"
+          :button-title="__('Insert suggestion')"
+          :cursor-offset="4"
+          :tag-content="lineContent"
+          icon="doc-code"
+          class="qa-suggestion-btn"
+        />
         <button
           v-gl-tooltip
           aria-label="Go full screen"
diff --git a/app/assets/javascripts/vue_shared/components/markdown/suggestion_diff.vue b/app/assets/javascripts/vue_shared/components/markdown/suggestion_diff.vue
new file mode 100644
index 00000000000..f98560f7336
--- /dev/null
+++ b/app/assets/javascripts/vue_shared/components/markdown/suggestion_diff.vue
@@ -0,0 +1,74 @@
+<script>
+import SuggestionDiffHeader from './suggestion_diff_header.vue';
+
+export default {
+  components: {
+    SuggestionDiffHeader,
+  },
+  props: {
+    newLines: {
+      type: Array,
+      required: true,
+    },
+    fromContent: {
+      type: String,
+      required: false,
+      default: '',
+    },
+    fromLine: {
+      type: Number,
+      required: true,
+    },
+    suggestion: {
+      type: Object,
+      required: true,
+    },
+    disabled: {
+      type: Boolean,
+      required: false,
+      default: false,
+    },
+    helpPagePath: {
+      type: String,
+      required: true,
+    },
+  },
+  methods: {
+    applySuggestion(callback) {
+      this.$emit('apply', { suggestionId: this.suggestion.id, callback });
+    },
+  },
+};
+</script>
+
+<template>
+  <div>
+    <suggestion-diff-header
+      class="qa-suggestion-diff-header"
+      :can-apply="suggestion.appliable && suggestion.current_user.can_apply && !disabled"
+      :is-applied="suggestion.applied"
+      :help-page-path="helpPagePath"
+      @apply="applySuggestion"
+    />
+    <table class="mb-3 md-suggestion-diff">
+      <tbody>
+        <!-- Old Line -->
+        <tr class="line_holder old">
+          <td class="diff-line-num old_line qa-old-diff-line-number old">{{ fromLine }}</td>
+          <td class="diff-line-num new_line old"></td>
+          <td class="line_content old">
+            <span>{{ fromContent }}</span>
+          </td>
+        </tr>
+        <!-- New Line(s) -->
+        <tr v-for="(line, key) of newLines" :key="key" class="line_holder new">
+          <td class="diff-line-num old_line new"></td>
+          <td class="diff-line-num new_line qa-new-diff-line-number new">{{ line.lineNumber }}</td>
+          <td class="line_content new">
+            <span>{{ line.content }}</span>
+          </td>
+        </tr>
+      </tbody>
+    </table>
+  </div>
+</template>
diff --git a/app/assets/javascripts/vue_shared/components/markdown/suggestion_diff_header.vue b/app/assets/javascripts/vue_shared/components/markdown/suggestion_diff_header.vue
new file mode 100644
index 00000000000..563e2f94fcc
--- /dev/null
+++ b/app/assets/javascripts/vue_shared/components/markdown/suggestion_diff_header.vue
@@ -0,0 +1,60 @@
+<script>
+import Icon from '~/vue_shared/components/icon.vue';
+
+export default {
+  components: { Icon },
+  props: {
+    canApply: {
+      type: Boolean,
+      required: false,
+      default: false,
+    },
+    isApplied: {
+      type: Boolean,
+      required: true,
+      default: false,
+    },
+    helpPagePath: {
+      type: String,
+      required: true,
+    },
+  },
+  data() {
+    return {
+      isAppliedSuccessfully: false,
+      isApplying: false,
+    };
+  },
+  methods: {
+    applySuggestion() {
+      if (!this.canApply) return;
+      this.isApplying = true;
+      this.$emit('apply', this.applySuggestionCallback);
+    },
+    applySuggestionCallback() {
+      this.isApplying = false;
+    },
+  },
+};
+</script>
+
+<template>
+  <div class="md-suggestion-header border-bottom-0 mt-2">
+    <div class="qa-suggestion-diff-header font-weight-bold">
+      {{ __('Suggested change') }}
+      <a v-if="helpPagePath" :href="helpPagePath" :aria-label="__('Help')">
+        <icon name="question-o" css-classes="link-highlight" />
+      </a>
+    </div>
+    <span v-if="isApplied" class="badge badge-success">{{ __('Applied') }}</span>
+    <button
+      v-if="canApply"
+      type="button"
+      class="btn qa-apply-btn"
+      :disabled="isApplying"
+      @click="applySuggestion"
+    >
+      {{ __('Apply suggestion') }}
+    </button>
+  </div>
+</template>
diff --git a/app/assets/javascripts/vue_shared/components/markdown/suggestions.vue b/app/assets/javascripts/vue_shared/components/markdown/suggestions.vue
new file mode 100644
index 00000000000..7c6dbee3e19
--- /dev/null
+++ b/app/assets/javascripts/vue_shared/components/markdown/suggestions.vue
@@ -0,0 +1,136 @@
+<script>
+import Vue from 'vue';
+import SuggestionDiff from './suggestion_diff.vue';
+import Flash from '~/flash';
+
+export default {
+  components: { SuggestionDiff },
+  props: {
+    fromLine: {
+      type: Number,
+      required: false,
+      default: 0,
+    },
+    fromContent: {
+      type: String,
+      required: false,
+      default: '',
+    },
+    lineType: {
+      type: String,
+      required: false,
+      default: '',
+    },
+    suggestions: {
+      type: Array,
+      required: false,
+      default: () => [],
+    },
+    noteHtml: {
+      type: String,
+      required: true,
+    },
+    disabled: {
+      type: Boolean,
+      required: false,
+      default: false,
+    },
+    helpPagePath: {
+      type: String,
+      required: true,
+    },
+  },
+  data() {
+    return {
+      isRendered: false,
+    };
+  },
+  watch: {
+    suggestions() {
+      this.reset();
+    },
+    noteHtml() {
+      this.reset();
+    },
+  },
+  mounted() {
+    this.renderSuggestions();
+  },
+  methods: {
+    renderSuggestions() {
+      // swaps out suggestion(s) markdown with rich diff components
+      // (while still keeping non-suggestion markdown in place)
+
+      if (!this.noteHtml) return;
+      const { container } = this.$refs;
+      const suggestionElements = container.querySelectorAll('.js-render-suggestion');
+
+      if (this.lineType === 'old') {
+        Flash('Unable to apply suggestions to a deleted line.', 'alert', this.$el);
+      }
+
+      suggestionElements.forEach((suggestionEl, i) => {
+        const suggestionParentEl = suggestionEl.parentElement;
+        const newLines = this.extractNewLines(suggestionParentEl);
+        const diffComponent = this.generateDiff(newLines, i);
+        diffComponent.$mount(suggestionParentEl);
+      });
+
+      this.isRendered = true;
+    },
+    extractNewLines(suggestionEl) {
+      // extracts the suggested lines from the markdown
+      // calculates a line number for each line
+
+      const FIRST_CHAR_REGEX = /^(\+|-)/;
+      const newLines = suggestionEl.querySelectorAll('.line');
+      const fromLine = this.suggestions.length ? this.suggestions[0].from_line : this.fromLine;
+      const lines = [];
+
+      newLines.forEach((line, i) => {
+        const content = `${line.innerText.replace(FIRST_CHAR_REGEX, '')}\n`;
+        const lineNumber = fromLine + i;
+        lines.push({ content, lineNumber });
+      });
+
+      return lines;
+    },
+    generateDiff(newLines, suggestionIndex) {
+      // generates the diff <suggestion-diff /> component
+      // all `suggestion` markdown will be swapped out by this component
+
+      const { suggestions, disabled, helpPagePath } = this;
+      const suggestion =
+        suggestions && suggestions[suggestionIndex] ? suggestions[suggestionIndex] : {};
+      const fromContent = suggestion.from_content || this.fromContent;
+      const fromLine = suggestion.from_line || this.fromLine;
+      const SuggestionDiffComponent = Vue.extend(SuggestionDiff);
+      const suggestionDiff = new SuggestionDiffComponent({
+        propsData: { newLines, fromLine, fromContent, disabled, suggestion, helpPagePath },
+      });
+
+      suggestionDiff.$on('apply', ({ suggestionId, callback }) => {
+        this.$emit('apply', { suggestionId, callback, flashContainer: this.$el });
+      });
+
+      return suggestionDiff;
+    },
+    reset() {
+      // resets the container HTML (replaces it with the updated noteHTML)
+      // calls `renderSuggestions` once the updated noteHTML is added to the DOM
+
+      this.$refs.container.innerHTML = this.noteHtml;
+      this.isRendered = false;
+      this.renderSuggestions();
+      this.$nextTick(() => this.renderSuggestions());
+    },
+  },
+};
+</script>
+
+<template>
+  <div>
+    <div class="flash-container mt-3"></div>
+    <div v-show="isRendered" ref="container" v-html="noteHtml"></div>
+  </div>
+</template>
diff --git a/app/assets/javascripts/vue_shared/components/markdown/toolbar_button.vue b/app/assets/javascripts/vue_shared/components/markdown/toolbar_button.vue
index a6d2cecdf7e..4572caa907b 100644
--- a/app/assets/javascripts/vue_shared/components/markdown/toolbar_button.vue
+++ b/app/assets/javascripts/vue_shared/components/markdown/toolbar_button.vue
@@ -37,6 +37,16 @@ export default {
       required: false,
       default: false,
     },
+    tagContent: {
+      type: String,
+      required: false,
+      default: '',
+    },
+    cursorOffset: {
+      type: Number,
+      required: false,
+      default: 0,
+    },
   },
 };
 </script>
@@ -45,8 +55,10 @@ export default {
   <button
     v-gl-tooltip
     :data-md-tag="tag"
+    :data-md-cursor-offset="cursorOffset"
     :data-md-select="tagSelect"
     :data-md-block="tagBlock"
+    :data-md-tag-content="tagContent"
     :data-md-prepend="prepend"
     :title="buttonTitle"
     :aria-label="buttonTitle"