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 bb66ab3628323e618a65004529da6194ba6d5dbb..41670b4579800da033769fb7cd8bc92fcbd3c95a 100644
--- a/app/assets/javascripts/diffs/components/diff_line_note_form.vue
+++ b/app/assets/javascripts/diffs/components/diff_line_note_form.vue
@@ -48,10 +48,13 @@ export default {
         noteableType: this.noteableType,
         noteTargetLine: this.noteTargetLine,
         diffViewType: this.diffViewType,
-        diffFile: this.getDiffFileByHash(this.diffFileHash),
+        diffFile: this.diffFile,
         linePosition: this.linePosition,
       };
     },
+    diffFile() {
+      return this.getDiffFileByHash(this.diffFileHash);
+    },
   },
   mounted() {
     if (this.isLoggedIn) {
@@ -102,6 +105,7 @@ export default {
       :line-code="line.line_code"
       :line="line"
       :help-page-path="helpPagePath"
+      :diff-file="diffFile"
       save-button-title="Comment"
       class="diff-comment-form"
       @handleFormUpdateAddToReview="addToReview"
diff --git a/app/assets/javascripts/notes/components/note_form.vue b/app/assets/javascripts/notes/components/note_form.vue
index 57d6b181bd7bd6b02f8f1ed6df4b9611e20a1f2c..471323bfc8336acb5fb603ad9b1c2b0a2ff5c321 100644
--- a/app/assets/javascripts/notes/components/note_form.vue
+++ b/app/assets/javascripts/notes/components/note_form.vue
@@ -61,6 +61,11 @@ export default {
       required: false,
       default: null,
     },
+    diffFile: {
+      type: Object,
+      required: false,
+      default: null,
+    },
     helpPagePath: {
       type: String,
       required: false,
@@ -102,9 +107,42 @@ export default {
       }
       return '#';
     },
+    diffParams() {
+      if (this.diffFile) {
+        return {
+          filePath: this.diffFile.file_path,
+          refs: this.diffFile.diff_refs,
+        };
+      } else if (this.note && this.note.position) {
+        return {
+          filePath: this.note.position.new_path,
+          refs: this.note.position,
+        };
+      } else if (this.discussion && this.discussion.diff_file) {
+        return {
+          filePath: this.discussion.diff_file.file_path,
+          refs: this.discussion.diff_file.diff_refs,
+        };
+      }
+
+      return null;
+    },
     markdownPreviewPath() {
       const notable = this.getNoteableDataByProp('preview_note_path');
-      return mergeUrlParams({ preview_suggestions: true }, notable);
+
+      const previewSuggestions = this.line && this.diffParams;
+      const params = previewSuggestions
+        ? {
+            preview_suggestions: previewSuggestions,
+            line: this.line.new_line,
+            file_path: this.diffParams.filePath,
+            base_sha: this.diffParams.refs.base_sha,
+            start_sha: this.diffParams.refs.start_sha,
+            head_sha: this.diffParams.refs.head_sha,
+          }
+        : {};
+
+      return mergeUrlParams(params, notable);
     },
     markdownDocsPath() {
       return this.getNotesDataByProp('markdownDocsPath');
@@ -234,8 +272,8 @@ export default {
           placeholder="Write a comment or drag your files here…"
           @keydown.meta.enter="handleKeySubmit()"
           @keydown.ctrl.enter="handleKeySubmit()"
-          @keydown.up="editMyLastNote()"
-          @keydown.esc="cancelHandler(true)"
+          @keydown.exact.up="editMyLastNote()"
+          @keydown.exact.esc="cancelHandler(true)"
           @input="onInput"
         ></textarea>
       </markdown-field>
diff --git a/app/assets/javascripts/vue_shared/components/lib/utils/diff_utils.js b/app/assets/javascripts/vue_shared/components/lib/utils/diff_utils.js
new file mode 100644
index 0000000000000000000000000000000000000000..d1aba99ac22f986b4a68c244feab3db7ad9fc536
--- /dev/null
+++ b/app/assets/javascripts/vue_shared/components/lib/utils/diff_utils.js
@@ -0,0 +1,20 @@
+/* eslint-disable import/prefer-default-export */
+
+function trimFirstCharOfLineContent(text) {
+  if (!text) {
+    return text;
+  }
+
+  return text.replace(/^( |\+|-)/, '');
+}
+
+function cleanSuggestionLine(line = {}) {
+  return {
+    ...line,
+    text: trimFirstCharOfLineContent(line.text),
+  };
+}
+
+export function selectDiffLines(lines) {
+  return lines.filter(line => line.type !== 'match').map(line => cleanSuggestionLine(line));
+}
diff --git a/app/assets/javascripts/vue_shared/components/markdown/field.vue b/app/assets/javascripts/vue_shared/components/markdown/field.vue
index eccf73e227c8c98977f3302ddba68e0312a92fb4..0f3b35684141a21e2a755f9764ee57f232751ed0 100644
--- a/app/assets/javascripts/vue_shared/components/markdown/field.vue
+++ b/app/assets/javascripts/vue_shared/components/markdown/field.vue
@@ -76,6 +76,7 @@ export default {
       hasSuggestion: false,
       markdownPreviewLoading: false,
       previewMarkdown: false,
+      suggestions: this.note.suggestions || [],
     };
   },
   computed: {
@@ -109,9 +110,6 @@ export default {
       }
       return lineNumber;
     },
-    suggestions() {
-      return this.note.suggestions || [];
-    },
     lineType() {
       return this.line ? this.line.type : '';
     },
@@ -175,6 +173,7 @@ export default {
         this.referencedCommands = data.references.commands;
         this.referencedUsers = data.references.users;
         this.hasSuggestion = data.references.suggestions && data.references.suggestions.length;
+        this.suggestions = data.references.suggestions;
       }
 
       this.$nextTick()
diff --git a/app/assets/javascripts/vue_shared/components/markdown/header.vue b/app/assets/javascripts/vue_shared/components/markdown/header.vue
index cc6ecdb0395d67193ef93edd4e93df9f9ecf003b..a5a5b2ef415b33e1134645e4c835c2e14809d483 100644
--- a/app/assets/javascripts/vue_shared/components/markdown/header.vue
+++ b/app/assets/javascripts/vue_shared/components/markdown/header.vue
@@ -38,7 +38,7 @@ export default {
       ].join('\n');
     },
     mdSuggestion() {
-      return ['```suggestion', `{text}`, '```'].join('\n');
+      return ['```suggestion:-0+0', `{text}`, '```'].join('\n');
     },
   },
   mounted() {
diff --git a/app/assets/javascripts/vue_shared/components/markdown/suggestion_diff.vue b/app/assets/javascripts/vue_shared/components/markdown/suggestion_diff.vue
index a351ca62c94bbfa38ebcf3017140a204d95552f0..2eb4ec12a4a52d36b9c7ece25338108eadc0f8aa 100644
--- a/app/assets/javascripts/vue_shared/components/markdown/suggestion_diff.vue
+++ b/app/assets/javascripts/vue_shared/components/markdown/suggestion_diff.vue
@@ -1,24 +1,14 @@
 <script>
 import SuggestionDiffHeader from './suggestion_diff_header.vue';
+import SuggestionDiffRow from './suggestion_diff_row.vue';
+import { selectDiffLines } from '../lib/utils/diff_utils';
 
 export default {
   components: {
     SuggestionDiffHeader,
+    SuggestionDiffRow,
   },
   props: {
-    newLines: {
-      type: Array,
-      required: true,
-    },
-    fromContent: {
-      type: String,
-      required: false,
-      default: '',
-    },
-    fromLine: {
-      type: Number,
-      required: true,
-    },
     suggestion: {
       type: Object,
       required: true,
@@ -33,6 +23,11 @@ export default {
       required: true,
     },
   },
+  computed: {
+    lines() {
+      return selectDiffLines(this.suggestion.diff_lines);
+    },
+  },
   methods: {
     applySuggestion(callback) {
       this.$emit('apply', { suggestionId: this.suggestion.id, callback });
@@ -52,22 +47,11 @@ export default {
     />
     <table class="mb-3 md-suggestion-diff js-syntax-highlight code">
       <tbody>
-        <!-- Old Line -->
-        <tr class="line_holder old">
-          <td class="diff-line-num old_line qa-old-diff-line-number old">{{ fromLine }}</td>
-          <td class="diff-line-num new_line old"></td>
-          <td class="line_content old">
-            <span>{{ fromContent }}</span>
-          </td>
-        </tr>
-        <!-- New Line(s) -->
-        <tr v-for="(line, key) of newLines" :key="key" class="line_holder new">
-          <td class="diff-line-num old_line new"></td>
-          <td class="diff-line-num new_line qa-new-diff-line-number new">{{ line.lineNumber }}</td>
-          <td class="line_content new">
-            <span>{{ line.content }}</span>
-          </td>
-        </tr>
+        <suggestion-diff-row
+          v-for="(line, index) of lines"
+          :key="`${index}-${line.text}`"
+          :line="line"
+        />
       </tbody>
     </table>
   </div>
diff --git a/app/assets/javascripts/vue_shared/components/markdown/suggestion_diff_row.vue b/app/assets/javascripts/vue_shared/components/markdown/suggestion_diff_row.vue
new file mode 100644
index 0000000000000000000000000000000000000000..cafd3a515ea9d11d2def5a2bbe7cc64b2734683f
--- /dev/null
+++ b/app/assets/javascripts/vue_shared/components/markdown/suggestion_diff_row.vue
@@ -0,0 +1,32 @@
+<script>
+export default {
+  name: 'SuggestionDiffRow',
+  props: {
+    line: {
+      type: Object,
+      required: true,
+    },
+  },
+  computed: {
+    lineType() {
+      return this.line.type;
+    },
+  },
+};
+</script>
+
+<template>
+  <tr class="line_holder" :class="lineType">
+    <td class="diff-line-num old_line" :class="lineType">
+      {{ line.old_line }}
+    </td>
+    <td class="diff-line-num new_line" :class="lineType">
+      {{ line.new_line }}
+    </td>
+    <td class="line_content" :class="lineType">
+      <span v-if="line.text">{{ line.text }}</span>
+      <!-- TODO: replace this hack with zero-width whitespace when we have rich_text from BE -->
+      <span v-else>&#8203;</span>
+    </td>
+  </tr>
+</template>
diff --git a/app/assets/javascripts/vue_shared/components/markdown/suggestions.vue b/app/assets/javascripts/vue_shared/components/markdown/suggestions.vue
index 177d78cb904a6c0e49309b00ee91d26edb040744..8d3705e1e4a114ec7258e9aabfba9e4d7fbedd9d 100644
--- a/app/assets/javascripts/vue_shared/components/markdown/suggestions.vue
+++ b/app/assets/javascripts/vue_shared/components/markdown/suggestions.vue
@@ -6,16 +6,6 @@ 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,
@@ -71,41 +61,19 @@ export default {
 
       suggestionElements.forEach((suggestionEl, i) => {
         const suggestionParentEl = suggestionEl.parentElement;
-        const newLines = this.extractNewLines(suggestionParentEl);
-        const diffComponent = this.generateDiff(newLines, i);
+        const diffComponent = this.generateDiff(i);
         diffComponent.$mount(suggestionParentEl);
       });
 
       this.isRendered = true;
     },
-    extractNewLines(suggestionEl) {
-      // extracts the suggested lines from the markdown
-      // calculates a line number for each line
-
-      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}\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
-
+    generateDiff(suggestionIndex) {
       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 },
+        propsData: { disabled, suggestion, helpPagePath },
       });
 
       suggestionDiff.$on('apply', ({ suggestionId, callback }) => {
diff --git a/app/controllers/concerns/preview_markdown.rb b/app/controllers/concerns/preview_markdown.rb
index f72d25fc54c4410668e66776aae7e0a1a9ffafb3..2a9729b6ffd7d9e7ca3366db08e9d070dada5d34 100644
--- a/app/controllers/concerns/preview_markdown.rb
+++ b/app/controllers/concerns/preview_markdown.rb
@@ -20,7 +20,7 @@ def preview_markdown
       body: view_context.markdown(result[:text], markdown_params),
       references: {
         users: result[:users],
-        suggestions: result[:suggestions],
+        suggestions: SuggestionSerializer.new.represent_diff(result[:suggestions]),
         commands: view_context.markdown(result[:commands])
       }
     }
diff --git a/app/serializers/issue_entity.rb b/app/serializers/issue_entity.rb
index c3f7d4651fb8f76d9676949db641514d36013b87..914ad628a99e5d9e9a81926cf7bf4b4e8cbbcd95 100644
--- a/app/serializers/issue_entity.rb
+++ b/app/serializers/issue_entity.rb
@@ -42,6 +42,6 @@ class IssueEntity < IssuableEntity
   end
 
   expose :preview_note_path do |issue|
-    preview_markdown_path(issue.project, quick_actions_target_type: 'Issue', quick_actions_target_id: issue.iid)
+    preview_markdown_path(issue.project, target_type: 'Issue', target_id: issue.iid)
   end
 end
diff --git a/app/serializers/merge_request_widget_entity.rb b/app/serializers/merge_request_widget_entity.rb
index d673f8ae89654fbe30ab97085f5f2391778290a7..4831eb32c9650fd8559156252d3737149a6511bd 100644
--- a/app/serializers/merge_request_widget_entity.rb
+++ b/app/serializers/merge_request_widget_entity.rb
@@ -235,7 +235,7 @@ class MergeRequestWidgetEntity < IssuableEntity
   end
 
   expose :preview_note_path do |merge_request|
-    preview_markdown_path(merge_request.project, quick_actions_target_type: 'MergeRequest', quick_actions_target_id: merge_request.iid)
+    preview_markdown_path(merge_request.project, target_type: 'MergeRequest', target_id: merge_request.iid)
   end
 
   expose :merge_commit_path do |merge_request|
diff --git a/app/serializers/suggestion_entity.rb b/app/serializers/suggestion_entity.rb
index 4d0d4da10bea944d3f598158dc84742fa13534b4..2dd62e19e29468edc0b6fd117e7f0c2cb6ab6d6b 100644
--- a/app/serializers/suggestion_entity.rb
+++ b/app/serializers/suggestion_entity.rb
@@ -3,6 +3,8 @@
 class SuggestionEntity < API::Entities::Suggestion
   include RequestAwareEntity
 
+  unexpose :from_line, :to_line, :from_content, :to_content
+  expose :diff_lines, using: DiffLineEntity
   expose :current_user do
     expose :can_apply do |suggestion|
       Ability.allowed?(current_user, :apply_suggestion, suggestion)
diff --git a/app/serializers/suggestion_serializer.rb b/app/serializers/suggestion_serializer.rb
new file mode 100644
index 0000000000000000000000000000000000000000..010344f9fcd4866e0a90d6055dc581d2593fa6e9
--- /dev/null
+++ b/app/serializers/suggestion_serializer.rb
@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+class SuggestionSerializer < BaseSerializer
+  entity SuggestionEntity
+
+  def represent_diff(resource)
+    represent(resource, { only: [:diff_lines] })
+  end
+end
diff --git a/app/services/concerns/suggestible.rb b/app/services/concerns/suggestible.rb
index 0b9822b19091b87fd2ceabedf870cff115ab6659..0cba9bf1b8acc0c0b84919f655c9a267e3768b67 100644
--- a/app/services/concerns/suggestible.rb
+++ b/app/services/concerns/suggestible.rb
@@ -2,10 +2,17 @@
 
 module Suggestible
   extend ActiveSupport::Concern
+  include Gitlab::Utils::StrongMemoize
 
   # This translates into limiting suggestion changes to `suggestion:-100+100`.
   MAX_LINES_CONTEXT = 100.freeze
 
+  def diff_lines
+    strong_memoize(:diff_lines) do
+      Gitlab::Diff::SuggestionDiff.new(self).diff_lines
+    end
+  end
+
   def fetch_from_content
     diff_file.new_blob_lines_between(from_line, to_line).join
   end
diff --git a/app/services/preview_markdown_service.rb b/app/services/preview_markdown_service.rb
index c1655c38095350a5ae67179b018bd35668fe1d32..7386530f45ff0c20dec30c4ad1cd694381c9c762 100644
--- a/app/services/preview_markdown_service.rb
+++ b/app/services/preview_markdown_service.rb
@@ -17,7 +17,7 @@ def execute
   private
 
   def explain_quick_actions(text)
-    return text, [] unless %w(Issue MergeRequest Commit).include?(commands_target_type)
+    return text, [] unless %w(Issue MergeRequest Commit).include?(target_type)
 
     quick_actions_service = QuickActions::InterpretService.new(project, current_user)
     quick_actions_service.explain(text, find_commands_target)
@@ -30,22 +30,34 @@ def find_user_references(text)
   end
 
   def find_suggestions(text)
-    return [] unless params[:preview_suggestions]
+    return [] unless preview_sugestions?
 
-    Banzai::SuggestionsParser.parse(text)
+    position = Gitlab::Diff::Position.new(new_path: params[:file_path],
+                                          new_line: params[:line].to_i,
+                                          base_sha: params[:base_sha],
+                                          head_sha: params[:head_sha],
+                                          start_sha: params[:start_sha])
+
+    Gitlab::Diff::SuggestionsParser.parse(text, position: position, project: project)
+  end
+
+  def preview_sugestions?
+    params[:preview_suggestions] &&
+      target_type == 'MergeRequest' &&
+      Ability.allowed?(current_user, :download_code, project)
   end
 
   def find_commands_target
     QuickActions::TargetService
       .new(project, current_user)
-      .execute(commands_target_type, commands_target_id)
+      .execute(target_type, target_id)
   end
 
-  def commands_target_type
-    params[:quick_actions_target_type]
+  def target_type
+    params[:target_type]
   end
 
-  def commands_target_id
-    params[:quick_actions_target_id]
+  def target_id
+    params[:target_id]
   end
 end
diff --git a/app/views/shared/form_elements/_description.html.haml b/app/views/shared/form_elements/_description.html.haml
index 25df2fe5cd6c57644a1181f99fd6a3cee8b002a2..b11cb8a3076d72eea1b5cbb714c3dfbed4d25bee 100644
--- a/app/views/shared/form_elements/_description.html.haml
+++ b/app/views/shared/form_elements/_description.html.haml
@@ -5,7 +5,7 @@
 - supports_quick_actions = model.new_record?
 
 - if supports_quick_actions
-  - preview_url = preview_markdown_path(project, quick_actions_target_type: model.class.name)
+  - preview_url = preview_markdown_path(project, target_type: model.class.name)
 - else
   - preview_url = preview_markdown_path(project)
 
diff --git a/app/views/shared/notes/_form.html.haml b/app/views/shared/notes/_form.html.haml
index 6a1eea85fded944d6e980cdff84806df43d59613..d91bc6e57c92b35106a01db24468dc692da684c4 100644
--- a/app/views/shared/notes/_form.html.haml
+++ b/app/views/shared/notes/_form.html.haml
@@ -1,7 +1,7 @@
 - supports_autocomplete = local_assigns.fetch(:supports_autocomplete, true)
 - supports_quick_actions = note_supports_quick_actions?(@note)
 - if supports_quick_actions
-  - preview_url = preview_markdown_path(@project, quick_actions_target_type: @note.noteable_type, quick_actions_target_id: @note.noteable_id)
+  - preview_url = preview_markdown_path(@project, target_type: @note.noteable_type, target_id: @note.noteable_id)
 - else
   - preview_url = preview_markdown_path(@project)
 
diff --git a/changelogs/unreleased/osw-support-multi-line-suggestions.yml b/changelogs/unreleased/osw-support-multi-line-suggestions.yml
new file mode 100644
index 0000000000000000000000000000000000000000..8c8206c3822ffb70603cd454fc3f8d33fd5a0c50
--- /dev/null
+++ b/changelogs/unreleased/osw-support-multi-line-suggestions.yml
@@ -0,0 +1,5 @@
+---
+title: Support multi-line suggestions
+merge_request: 25211
+author:
+type: added
diff --git a/doc/user/discussions/img/multi-line-suggestion-preview.png b/doc/user/discussions/img/multi-line-suggestion-preview.png
new file mode 100644
index 0000000000000000000000000000000000000000..4288d0ba034b29fec5c2ebb03f905aa7cede7bd2
Binary files /dev/null and b/doc/user/discussions/img/multi-line-suggestion-preview.png differ
diff --git a/doc/user/discussions/img/multi-line-suggestion-syntax.png b/doc/user/discussions/img/multi-line-suggestion-syntax.png
new file mode 100644
index 0000000000000000000000000000000000000000..df0c99b84ef48aaa60b1f8dbdaa7afb574116efc
Binary files /dev/null and b/doc/user/discussions/img/multi-line-suggestion-syntax.png differ
diff --git a/doc/user/discussions/index.md b/doc/user/discussions/index.md
index 23b9604a45687a54d769cae620f1890a6bceb8c9..bf41fdecd10ba69a39e25436d10c644893a343bf 100644
--- a/doc/user/discussions/index.md
+++ b/doc/user/discussions/index.md
@@ -344,6 +344,24 @@ and push the suggested change directly into the codebase in the merge request's
 Custom commit messages will be introduced by
 [#54404](https://gitlab.com/gitlab-org/gitlab-ce/issues/54404).
 
+### Multi-line suggestions
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab-ce/issues/53310) in GitLab 11.10.
+
+Reviewers can also suggest changes to
+multiple lines with a single suggestion within Merge Request diff discussions.
+
+![Multi-line suggestion syntax](img/multi-line-suggestion-syntax.png)
+
+In the example above, the suggestion covers three lines above and four lines below the commented diff line.
+It'd change from 3 lines _above_ to 4 lines _below_ the commented Diff line.
+
+![Multi-line suggestion preview](img/multi-line-suggestion-preview.png)
+
+NOTE: **Note:**
+Suggestions covering multiple lines are limited to 100 lines _above_ and 100 lines _below_ 
+the commented diff line, allowing up to 200 changed lines per suggestion.
+
 ## Start a discussion by replying to a standard comment
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab-ce/issues/30299) in GitLab 11.9
diff --git a/lib/banzai/suggestions_parser.rb b/lib/banzai/suggestions_parser.rb
deleted file mode 100644
index 0d7f751bfc1aac66c2b30cde024009f2db2c8be2..0000000000000000000000000000000000000000
--- a/lib/banzai/suggestions_parser.rb
+++ /dev/null
@@ -1,16 +0,0 @@
-# frozen_string_literal: true
-
-# TODO: Delete when https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/26107
-# exchange this parser by `Gitlab::Diff::SuggestionsParser`.
-module Banzai
-  module SuggestionsParser
-    # Returns the content of each suggestion code block.
-    #
-    def self.parse(text)
-      html = Banzai.render(text, project: nil, no_original_data: true)
-      doc = Nokogiri::HTML(html)
-
-      doc.search('pre.suggestion').map { |node| node.text }
-    end
-  end
-end
diff --git a/spec/controllers/projects_controller_spec.rb b/spec/controllers/projects_controller_spec.rb
index 356d606d5c5d68e61e2885c11a03e59758253856..56d38b9475e0e2c04f616a91e46bf2e3c0c7bb25 100644
--- a/spec/controllers/projects_controller_spec.rb
+++ b/spec/controllers/projects_controller_spec.rb
@@ -703,6 +703,16 @@ def update_project(**parameters)
       expect(JSON.parse(response.body).keys).to match_array(%w(body references))
     end
 
+    context 'when not authorized' do
+      let(:private_project) { create(:project, :private) }
+
+      it 'returns 404' do
+        post :preview_markdown, params: { namespace_id: private_project.namespace, id: private_project, text: '*Markdown* text' }
+
+        expect(response).to have_gitlab_http_status(404)
+      end
+    end
+
     context 'state filter on references' do
       let(:issue) { create(:issue, :closed, project: public_project) }
       let(:merge_request) { create(:merge_request, :closed, target_project: public_project) }
diff --git a/spec/features/merge_request/user_suggests_changes_on_diff_spec.rb b/spec/features/merge_request/user_suggests_changes_on_diff_spec.rb
index c19e299097e3b2a1c847162eb9b32cf4614611f5..1b5dd6945e0b7b399340068b37e98a6ae88ed3a3 100644
--- a/spec/features/merge_request/user_suggests_changes_on_diff_spec.rb
+++ b/spec/features/merge_request/user_suggests_changes_on_diff_spec.rb
@@ -6,6 +6,14 @@
   include MergeRequestDiffHelpers
   include RepoHelpers
 
+  def expect_suggestion_has_content(element, expected_changing_content, expected_suggested_content)
+    changing_content = element.all(:css, '.line_holder.old').map(&:text)
+    suggested_content = element.all(:css, '.line_holder.new').map(&:text)
+
+    expect(changing_content).to eq(expected_changing_content)
+    expect(suggested_content).to eq(expected_suggested_content)
+  end
+
   let(:project) { create(:project, :repository) }
   let(:merge_request) do
     create(:merge_request_with_diffs, source_project: project, target_project: project, source_branch: 'merge-test')
@@ -33,8 +41,18 @@
       page.within('.diff-discussions') do
         expect(page).to have_button('Apply suggestion')
         expect(page).to have_content('Suggested change')
-        expect(page).to have_content('	url = https://github.com/gitlabhq/gitlab-shell.git')
-        expect(page).to have_content('# change to a comment')
+      end
+
+      page.within('.md-suggestion-diff') do
+        expected_changing_content = [
+          "6 url = https://github.com/gitlabhq/gitlab-shell.git"
+        ]
+
+        expected_suggested_content = [
+          "6 # change to a comment"
+        ]
+
+        expect_suggestion_has_content(page, expected_changing_content, expected_suggested_content)
       end
     end
 
@@ -64,7 +82,7 @@
       click_diff_line(find("[id='#{sample_compare.changes[1][:line_code]}']"))
 
       page.within('.js-discussion-note-form') do
-        fill_in('note_note', with: "```suggestion\n# change to a comment\n```\n```suggestion\n# or that\n```")
+        fill_in('note_note', with: "```suggestion\n# change to a comment\n```\n```suggestion:-2\n# or that\n# heh\n```")
         click_button('Comment')
       end
 
@@ -74,11 +92,90 @@
         suggestion_1 = page.all(:css, '.md-suggestion-diff')[0]
         suggestion_2 = page.all(:css, '.md-suggestion-diff')[1]
 
-        expect(suggestion_1).to have_content('	url = https://github.com/gitlabhq/gitlab-shell.git')
-        expect(suggestion_1).to have_content('# change to a comment')
+        suggestion_1_expected_changing_content = [
+          "6 url = https://github.com/gitlabhq/gitlab-shell.git"
+        ]
+        suggestion_1_expected_suggested_content = [
+          "6 # change to a comment"
+        ]
+
+        suggestion_2_expected_changing_content = [
+          "4 [submodule \"gitlab-shell\"]",
+          "5 path = gitlab-shell",
+          "6 url = https://github.com/gitlabhq/gitlab-shell.git"
+        ]
+        suggestion_2_expected_suggested_content = [
+          "4 # or that",
+          "5 # heh"
+        ]
+
+        expect_suggestion_has_content(suggestion_1,
+                                      suggestion_1_expected_changing_content,
+                                      suggestion_1_expected_suggested_content)
+
+        expect_suggestion_has_content(suggestion_2,
+                                      suggestion_2_expected_changing_content,
+                                      suggestion_2_expected_suggested_content)
+      end
+    end
+  end
+
+  context 'multi-line suggestions' do
+    it 'suggestion is presented' do
+      click_diff_line(find("[id='#{sample_compare.changes[1][:line_code]}']"))
+
+      page.within('.js-discussion-note-form') do
+        fill_in('note_note', with: "```suggestion:-3+5\n# change to a\n# comment\n# with\n# broken\n# lines\n```")
+        click_button('Comment')
+      end
 
-        expect(suggestion_2).to have_content('	url = https://github.com/gitlabhq/gitlab-shell.git')
-        expect(suggestion_2).to have_content('# or that')
+      wait_for_requests
+
+      page.within('.diff-discussions') do
+        expect(page).to have_button('Apply suggestion')
+        expect(page).to have_content('Suggested change')
+      end
+
+      page.within('.md-suggestion-diff') do
+        expected_changing_content = [
+          "3 url = git://github.com/randx/six.git",
+          "4 [submodule \"gitlab-shell\"]",
+          "5 path = gitlab-shell",
+          "6 url = https://github.com/gitlabhq/gitlab-shell.git",
+          "7 [submodule \"gitlab-grack\"]",
+          "8 path = gitlab-grack",
+          "9 url = https://gitlab.com/gitlab-org/gitlab-grack.git"
+        ]
+
+        expected_suggested_content = [
+          "3 # change to a",
+          "4 # comment",
+          "5 # with",
+          "6 # broken",
+          "7 # lines"
+        ]
+
+        expect_suggestion_has_content(page, expected_changing_content, expected_suggested_content)
+      end
+    end
+
+    it 'suggestion is appliable' do
+      click_diff_line(find("[id='#{sample_compare.changes[1][:line_code]}']"))
+
+      page.within('.js-discussion-note-form') do
+        fill_in('note_note', with: "```suggestion:-3+5\n# change to a\n# comment\n# with\n# broken\n# lines\n```")
+        click_button('Comment')
+      end
+
+      wait_for_requests
+
+      page.within('.diff-discussions') do
+        expect(page).not_to have_content('Applied')
+
+        click_button('Apply suggestion')
+        wait_for_requests
+
+        expect(page).to have_content('Applied')
       end
     end
   end
diff --git a/spec/frontend/vue_shared/components/markdown/suggestion_diff_row_spec.js b/spec/frontend/vue_shared/components/markdown/suggestion_diff_row_spec.js
new file mode 100644
index 0000000000000000000000000000000000000000..866d6eb05c636d8e5b9064f75bdeb8357f349ee3
--- /dev/null
+++ b/spec/frontend/vue_shared/components/markdown/suggestion_diff_row_spec.js
@@ -0,0 +1,98 @@
+import { shallowMount, createLocalVue } from '@vue/test-utils';
+import SuggestionDiffRow from '~/vue_shared/components/markdown/suggestion_diff_row.vue';
+
+const oldLine = {
+  can_receive_suggestion: false,
+  line_code: null,
+  meta_data: null,
+  new_line: null,
+  old_line: 5,
+  rich_text: '-oldtext',
+  text: '-oldtext',
+  type: 'old',
+};
+
+const newLine = {
+  can_receive_suggestion: false,
+  line_code: null,
+  meta_data: null,
+  new_line: 6,
+  old_line: null,
+  rich_text: '-newtext',
+  text: '-newtext',
+  type: 'new',
+};
+
+describe(SuggestionDiffRow.name, () => {
+  let wrapper;
+
+  const factory = (options = {}) => {
+    const localVue = createLocalVue();
+
+    wrapper = shallowMount(SuggestionDiffRow, {
+      localVue,
+      ...options,
+    });
+  };
+
+  const findOldLineWrapper = () => wrapper.find('.old_line');
+  const findNewLineWrapper = () => wrapper.find('.new_line');
+
+  afterEach(() => {
+    wrapper.destroy();
+  });
+
+  it('renders correctly', () => {
+    factory({
+      propsData: {
+        line: oldLine,
+      },
+    });
+
+    expect(wrapper.is('.line_holder')).toBe(true);
+  });
+
+  describe('when passed line has type old', () => {
+    beforeEach(() => {
+      factory({
+        propsData: {
+          line: oldLine,
+        },
+      });
+    });
+
+    it('has old class when line has type old', () => {
+      expect(wrapper.find('td').classes()).toContain('old');
+    });
+
+    it('has old line number rendered', () => {
+      expect(findOldLineWrapper().text()).toBe('5');
+    });
+
+    it('has no new line number rendered', () => {
+      expect(findNewLineWrapper().text()).toBe('');
+    });
+  });
+
+  describe('when passed line has type new', () => {
+    beforeEach(() => {
+      factory({
+        propsData: {
+          line: newLine,
+        },
+      });
+    });
+
+    it('has new class when line has type new', () => {
+      expect(wrapper.find('td').classes()).toContain('new');
+    });
+
+    it('has no old line number rendered', () => {
+      expect(findOldLineWrapper().text()).toBe('');
+    });
+
+    it('has no new line number rendered', () => {
+      expect(findNewLineWrapper().text()).toBe('6');
+    });
+  });
+});
diff --git a/spec/javascripts/notes/mock_data.js b/spec/javascripts/notes/mock_data.js
index 348743081eb5d688107014f2c323e399aa463065..1df5cf9ef684774005c30ca9c5a09be462a1eea9 100644
--- a/spec/javascripts/notes/mock_data.js
+++ b/spec/javascripts/notes/mock_data.js
@@ -44,8 +44,7 @@ export const noteableDataMock = {
   milestone: null,
   milestone_id: null,
   moved_to_id: null,
-  preview_note_path:
-    '/gitlab-org/gitlab-ce/preview_markdown?quick_actions_target_id=98&quick_actions_target_type=Issue',
+  preview_note_path: '/gitlab-org/gitlab-ce/preview_markdown?target_id=98&target_type=Issue',
   project_id: 2,
   state: 'opened',
   time_estimate: 0,
@@ -347,8 +346,7 @@ export const loggedOutnoteableData = {
   },
   noteable_note_url: '/group/project/merge_requests/1#note_1',
   create_note_path: '/gitlab-org/gitlab-ce/notes?target_id=98&target_type=issue',
-  preview_note_path:
-    '/gitlab-org/gitlab-ce/preview_markdown?quick_actions_target_id=98&quick_actions_target_type=Issue',
+  preview_note_path: '/gitlab-org/gitlab-ce/preview_markdown?target_id=98&target_type=Issue',
 };
 
 export const collapseNotesMock = [
diff --git a/spec/javascripts/vue_shared/components/markdown/header_spec.js b/spec/javascripts/vue_shared/components/markdown/header_spec.js
index e733a95288ec18f15eb534d78f078b8e40425514..d4be2451f0b9f9e2c25fda31265c1058153d6818 100644
--- a/spec/javascripts/vue_shared/components/markdown/header_spec.js
+++ b/spec/javascripts/vue_shared/components/markdown/header_spec.js
@@ -98,7 +98,7 @@ describe('Markdown field header component', () => {
   it('renders suggestion template', () => {
     vm.lineContent = 'Some content';
 
-    expect(vm.mdSuggestion).toEqual('```suggestion\n{text}\n```');
+    expect(vm.mdSuggestion).toEqual('```suggestion:-0+0\n{text}\n```');
   });
 
   it('does not render suggestion button if `canSuggest` is set to false', () => {
diff --git a/spec/javascripts/vue_shared/components/markdown/suggestion_diff_spec.js b/spec/javascripts/vue_shared/components/markdown/suggestion_diff_spec.js
index f87c2a92f472b34c2b104892b5f752874065b6a3..ea74cb9eb21c3839a2b43474f5358a9918a48668 100644
--- a/spec/javascripts/vue_shared/components/markdown/suggestion_diff_spec.js
+++ b/spec/javascripts/vue_shared/components/markdown/suggestion_diff_spec.js
@@ -1,21 +1,50 @@
 import Vue from 'vue';
 import SuggestionDiffComponent from '~/vue_shared/components/markdown/suggestion_diff.vue';
+import { selectDiffLines } from '~/vue_shared/components/lib/utils/diff_utils';
 
 const MOCK_DATA = {
   canApply: true,
-  newLines: [
-    { content: 'Line 1\n', lineNumber: 1 },
-    { content: 'Line 2\n', lineNumber: 2 },
-    { content: 'Line 3\n', lineNumber: 3 },
-  ],
-  fromLine: 1,
-  fromContent: 'Old content',
   suggestion: {
     id: 1,
+    diff_lines: [
+      {
+        can_receive_suggestion: false,
+        line_code: null,
+        meta_data: null,
+        new_line: null,
+        old_line: 5,
+        rich_text: '-test',
+        text: '-test',
+        type: 'old',
+      },
+      {
+        can_receive_suggestion: true,
+        line_code: null,
+        meta_data: null,
+        new_line: 5,
+        old_line: null,
+        rich_text: '+new test',
+        text: '+new test',
+        type: 'new',
+      },
+      {
+        can_receive_suggestion: true,
+        line_code: null,
+        meta_data: null,
+        new_line: 5,
+        old_line: null,
+        rich_text: '+new test2',
+        text: '+new test2',
+        type: 'new',
+      },
+    ],
   },
   helpPagePath: 'path_to_docs',
 };
 
+const lines = selectDiffLines(MOCK_DATA.suggestion.diff_lines);
+const newLines = lines.filter(line => line.type === 'new');
+
 describe('Suggestion Diff component', () => {
   let vm;
 
@@ -39,30 +68,23 @@ describe('Suggestion Diff component', () => {
     });
 
     it('renders the oldLineNumber', () => {
-      const fromLine = vm.$el.querySelector('.qa-old-diff-line-number').innerHTML;
+      const fromLine = vm.$el.querySelector('.old_line').innerHTML;
 
-      expect(parseInt(fromLine, 10)).toBe(vm.fromLine);
+      expect(parseInt(fromLine, 10)).toBe(lines[0].old_line);
     });
 
     it('renders the oldLineContent', () => {
       const fromContent = vm.$el.querySelector('.line_content.old').innerHTML;
 
-      expect(fromContent.includes(vm.fromContent)).toBe(true);
-    });
-
-    it('renders the contents of newLines', () => {
-      const newLines = vm.$el.querySelectorAll('.line_holder.new');
-
-      newLines.forEach((line, i) => {
-        expect(newLines[i].innerHTML.includes(vm.newLines[i].content)).toBe(true);
-      });
+      expect(fromContent.includes(lines[0].text)).toBe(true);
     });
 
-    it('renders a line number for each line', () => {
-      const newLineNumbers = vm.$el.querySelectorAll('.qa-new-diff-line-number');
+    it('renders new lines', () => {
+      const newLinesElements = vm.$el.querySelectorAll('.line_holder.new');
 
-      newLineNumbers.forEach((line, i) => {
-        expect(newLineNumbers[i].innerHTML.includes(vm.newLines[i].lineNumber)).toBe(true);
+      newLinesElements.forEach((line, i) => {
+        expect(newLinesElements[i].innerHTML.includes(newLines[i].new_line)).toBe(true);
+        expect(newLinesElements[i].innerHTML.includes(newLines[i].text)).toBe(true);
       });
     });
   });
diff --git a/spec/javascripts/vue_shared/components/markdown/suggestions_spec.js b/spec/javascripts/vue_shared/components/markdown/suggestions_spec.js
index 33be63a3a1e48ad744f22231d3047a78c7a5bfbf..b7de40b483120ade6916319413bb482ffccf3d59 100644
--- a/spec/javascripts/vue_shared/components/markdown/suggestions_spec.js
+++ b/spec/javascripts/vue_shared/components/markdown/suggestions_spec.js
@@ -2,46 +2,52 @@ import Vue from 'vue';
 import SuggestionsComponent from '~/vue_shared/components/markdown/suggestions.vue';
 
 const MOCK_DATA = {
-  fromLine: 1,
-  fromContent: 'Old content',
-  suggestions: [],
+  suggestions: [
+    {
+      id: 1,
+      appliable: true,
+      applied: false,
+      current_user: {
+        can_apply: true,
+      },
+      diff_lines: [
+        {
+          can_receive_suggestion: false,
+          line_code: null,
+          meta_data: null,
+          new_line: null,
+          old_line: 5,
+          rich_text: '-test',
+          text: '-test',
+          type: 'old',
+        },
+        {
+          can_receive_suggestion: true,
+          line_code: null,
+          meta_data: null,
+          new_line: 5,
+          old_line: null,
+          rich_text: '+new test',
+          text: '+new test',
+          type: 'new',
+        },
+      ],
+    },
+  ],
   noteHtml: `
+      <div class="suggestion">
+      <div class="line">-oldtest</div>
+    </div>  
     <div class="suggestion">
-      <div class="line">Suggestion 1</div>
+      <div class="line">+newtest</div>
     </div>    
-    
-    <div class="suggestion">
-      <div class="line">Suggestion 2</div>
-    </div>
   `,
   isApplied: false,
   helpPagePath: 'path_to_docs',
 };
 
-const generateLine = content => {
-  const line = document.createElement('div');
-  line.className = 'line';
-  line.innerHTML = content;
-
-  return line;
-};
-
-const generateMockLines = () => {
-  const line1 = generateLine('Line 1');
-  const line2 = generateLine('Line 2');
-  const line3 = generateLine('- Line 3');
-  const container = document.createElement('div');
-
-  container.appendChild(line1);
-  container.appendChild(line2);
-  container.appendChild(line3);
-
-  return container;
-};
-
 describe('Suggestion component', () => {
   let vm;
-  let extractedLines;
   let diffTable;
 
   beforeEach(done => {
@@ -51,8 +57,7 @@ describe('Suggestion component', () => {
       propsData: MOCK_DATA,
     }).$mount();
 
-    extractedLines = vm.extractNewLines(generateMockLines());
-    diffTable = vm.generateDiff(extractedLines).$mount().$el;
+    diffTable = vm.generateDiff(0).$mount().$el;
 
     spyOn(vm, 'renderSuggestions');
     vm.renderSuggestions();
@@ -70,32 +75,8 @@ describe('Suggestion component', () => {
 
     it('renders suggestions', () => {
       expect(vm.renderSuggestions).toHaveBeenCalled();
-      expect(vm.$el.innerHTML.includes('Suggestion 1')).toBe(true);
-      expect(vm.$el.innerHTML.includes('Suggestion 2')).toBe(true);
-    });
-  });
-
-  describe('extractNewLines', () => {
-    it('extracts suggested lines', () => {
-      const expectedReturn = [
-        { content: 'Line 1\n', lineNumber: 1 },
-        { content: 'Line 2\n', lineNumber: 2 },
-        { content: '- Line 3\n', lineNumber: 3 },
-      ];
-
-      expect(vm.extractNewLines(generateMockLines())).toEqual(expectedReturn);
-    });
-
-    it('increments line number for each extracted line', () => {
-      expect(extractedLines[0].lineNumber).toEqual(1);
-      expect(extractedLines[1].lineNumber).toEqual(2);
-      expect(extractedLines[2].lineNumber).toEqual(3);
-    });
-
-    it('returns empty array if no lines are found', () => {
-      const el = document.createElement('div');
-
-      expect(vm.extractNewLines(el)).toEqual([]);
+      expect(vm.$el.innerHTML.includes('oldtest')).toBe(true);
+      expect(vm.$el.innerHTML.includes('newtest')).toBe(true);
     });
   });
 
@@ -109,17 +90,17 @@ describe('Suggestion component', () => {
     });
 
     it('generates a diff table that contains contents the suggested lines', () => {
-      extractedLines.forEach((line, i) => {
-        expect(diffTable.innerHTML.includes(extractedLines[i].content)).toBe(true);
+      MOCK_DATA.suggestions[0].diff_lines.forEach(line => {
+        const text = line.text.substring(1);
+
+        expect(diffTable.innerHTML.includes(text)).toBe(true);
       });
     });
 
     it('generates a diff table with the correct line number for each suggested line', () => {
-      const lines = diffTable.getElementsByClassName('qa-new-diff-line-number');
+      const lines = diffTable.querySelectorAll('.old_line');
 
-      expect([...lines][0].innerHTML).toBe('1');
-      expect([...lines][1].innerHTML).toBe('2');
-      expect([...lines][2].innerHTML).toBe('3');
+      expect(parseInt([...lines][0].innerHTML, 10)).toBe(5);
     });
   });
 });
diff --git a/spec/lib/banzai/suggestions_parser_spec.rb b/spec/lib/banzai/suggestions_parser_spec.rb
deleted file mode 100644
index 79658d710ce2f9afb82328412f4ebfa324d37cc1..0000000000000000000000000000000000000000
--- a/spec/lib/banzai/suggestions_parser_spec.rb
+++ /dev/null
@@ -1,32 +0,0 @@
-# frozen_string_literal: true
-
-require 'spec_helper'
-
-describe Banzai::SuggestionsParser do
-  describe '.parse' do
-    it 'returns a list of suggestion contents' do
-      markdown = <<-MARKDOWN.strip_heredoc
-        ```suggestion
-          foo
-          bar
-        ```
-
-        ```
-          nothing
-        ```
-
-        ```suggestion
-          xpto
-          baz
-        ```
-
-        ```thing
-          this is not a suggestion, it's a thing
-        ```
-      MARKDOWN
-
-      expect(described_class.parse(markdown)).to eq(["  foo\n  bar",
-                                                     "  xpto\n  baz"])
-    end
-  end
-end
diff --git a/spec/lib/gitlab/diff/suggestion_spec.rb b/spec/lib/gitlab/diff/suggestion_spec.rb
index 71fd25df6981a673830877b08c374f3a18552e12..d7ca0e0a52291a02864a429d55d590921f87df71 100644
--- a/spec/lib/gitlab/diff/suggestion_spec.rb
+++ b/spec/lib/gitlab/diff/suggestion_spec.rb
@@ -10,6 +10,16 @@
                                             lines_above: above,
                                             lines_below: below)
     end
+
+    it 'returns diff lines with correct line numbers' do
+      diff_lines = suggestion.diff_lines
+
+      expect(diff_lines).to all(be_a(Gitlab::Diff::Line))
+
+      expected_diff_lines.each_with_index do |expected_line, index|
+        expect(diff_lines[index].to_hash).to include(expected_line)
+      end
+    end
   end
 
   let(:merge_request) { create(:merge_request) }
@@ -48,6 +58,18 @@ def blob_data
       let(:expected_above) { line - 1 }
       let(:expected_below) { below }
       let(:expected_lines) { blob_lines_data(line - expected_above, line + expected_below) }
+      let(:expected_diff_lines) do
+        [
+          { old_pos: 1, new_pos: 1, type: 'old', text: "-require 'fileutils'" },
+          { old_pos: 2, new_pos: 1, type: 'old', text: "-require 'open3'" },
+          { old_pos: 3, new_pos: 1, type: 'old', text: "-" },
+          { old_pos: 4, new_pos: 1, type: 'old', text: "-module Popen" },
+          { old_pos: 5, new_pos: 1, type: 'old', text: "-  extend self" },
+          { old_pos: 6, new_pos: 1, type: 'old', text: "-" },
+          { old_pos: 7, new_pos: 1, type: 'new', text: "+# parsed suggestion content" },
+          { old_pos: 7, new_pos: 2, type: 'new', text: "+# with comments" }
+        ]
+      end
 
       it_behaves_like 'correct suggestion raw content'
     end
@@ -59,6 +81,47 @@ def blob_data
       let(:expected_below) { below }
       let(:expected_above) { above }
       let(:expected_lines) { blob_lines_data(line - expected_above, line + expected_below) }
+      let(:expected_diff_lines) do
+        [
+          { old_pos: 4, new_pos: 4, type: "match", text: "@@ -4 +4" },
+          { old_pos: 4, new_pos: 4, type: "old", text: "-module Popen" },
+          { old_pos: 5, new_pos: 4, type: "old", text: "-  extend self" },
+          { old_pos: 6, new_pos: 4, type: "old", text: "-" },
+          { old_pos: 7, new_pos: 4, type: "old", text: "-  def popen(cmd, path=nil)" },
+          { old_pos: 8, new_pos: 4, type: "old", text: "-    unless cmd.is_a?(Array)" },
+          { old_pos: 9, new_pos: 4, type: "old", text: "-      raise RuntimeError, \"System commands must be given as an array of strings\"" },
+          { old_pos: 10, new_pos: 4, type: "old", text: "-    end" },
+          { old_pos: 11, new_pos: 4, type: "old", text: "-" },
+          { old_pos: 12, new_pos: 4, type: "old", text: "-    path ||= Dir.pwd" },
+          { old_pos: 13, new_pos: 4, type: "old", text: "-" },
+          { old_pos: 14, new_pos: 4, type: "old", text: "-    vars = {" },
+          { old_pos: 15, new_pos: 4, type: "old", text: "-      \"PWD\" => path" },
+          { old_pos: 16, new_pos: 4, type: "old", text: "-    }" },
+          { old_pos: 17, new_pos: 4, type: "old", text: "-" },
+          { old_pos: 18, new_pos: 4, type: "old", text: "-    options = {" },
+          { old_pos: 19, new_pos: 4, type: "old", text: "-      chdir: path" },
+          { old_pos: 20, new_pos: 4, type: "old", text: "-    }" },
+          { old_pos: 21, new_pos: 4, type: "old", text: "-" },
+          { old_pos: 22, new_pos: 4, type: "old", text: "-    unless File.directory?(path)" },
+          { old_pos: 23, new_pos: 4, type: "old", text: "-      FileUtils.mkdir_p(path)" },
+          { old_pos: 24, new_pos: 4, type: "old", text: "-    end" },
+          { old_pos: 25, new_pos: 4, type: "old", text: "-" },
+          { old_pos: 26, new_pos: 4, type: "old", text: "-    @cmd_output = \"\"" },
+          { old_pos: 27, new_pos: 4, type: "old", text: "-    @cmd_status = 0" },
+          { old_pos: 28, new_pos: 4, type: "old", text: "-" },
+          { old_pos: 29, new_pos: 4, type: "old", text: "-    Open3.popen3(vars, *cmd, options) do |stdin, stdout, stderr, wait_thr|" },
+          { old_pos: 30, new_pos: 4, type: "old", text: "-      @cmd_output << stdout.read" },
+          { old_pos: 31, new_pos: 4, type: "old", text: "-      @cmd_output << stderr.read" },
+          { old_pos: 32, new_pos: 4, type: "old", text: "-      @cmd_status = wait_thr.value.exitstatus" },
+          { old_pos: 33, new_pos: 4, type: "old", text: "-    end" },
+          { old_pos: 34, new_pos: 4, type: "old", text: "-" },
+          { old_pos: 35, new_pos: 4, type: "old", text: "-    return @cmd_output, @cmd_status" },
+          { old_pos: 36, new_pos: 4, type: "old", text: "-  end" },
+          { old_pos: 37, new_pos: 4, type: "old", text: "-end" },
+          { old_pos: 38, new_pos: 4, type: "new", text: "+# parsed suggestion content" },
+          { old_pos: 38, new_pos: 5, type: "new", text: "+# with comments" }
+        ]
+      end
 
       it_behaves_like 'correct suggestion raw content'
     end
@@ -70,17 +133,19 @@ def blob_data
       let(:expected_below) { below }
       let(:expected_above) { above }
       let(:expected_lines) { blob_lines_data(line - expected_above, line + expected_below) }
-
-      it_behaves_like 'correct suggestion raw content'
-    end
-
-    context 'when no extra lines (single-line suggestion)' do
-      let(:line) { 5 }
-      let(:above) { 0 }
-      let(:below) { 0 }
-      let(:expected_below) { below }
-      let(:expected_above) { above }
-      let(:expected_lines) { blob_lines_data(line - expected_above, line + expected_below) }
+      let(:expected_diff_lines) do
+        [
+          { old_pos: 3, new_pos: 3, type: "match", text: "@@ -3 +3" },
+          { old_pos: 3, new_pos: 3, type: "old", text: "-" },
+          { old_pos: 4, new_pos: 3, type: "old", text: "-module Popen" },
+          { old_pos: 5, new_pos: 3, type: "old", text: "-  extend self" },
+          { old_pos: 6, new_pos: 3, type: "old", text: "-" },
+          { old_pos: 7, new_pos: 3, type: "old", text: "-  def popen(cmd, path=nil)" },
+          { old_pos: 8, new_pos: 3, type: "old", text: "-    unless cmd.is_a?(Array)" },
+          { old_pos: 9, new_pos: 3, type: "new", text: "+# parsed suggestion content" },
+          { old_pos: 9, new_pos: 4, type: "new", text: "+# with comments" }
+        ]
+      end
 
       it_behaves_like 'correct suggestion raw content'
     end
diff --git a/spec/lib/gitlab/diff/suggestions_parser_spec.rb b/spec/lib/gitlab/diff/suggestions_parser_spec.rb
index 1119ea04995756dd3b426c86b0ba534ad4cc67c9..1f2af42f6e785556a768630f06ebd73a50bc6942 100644
--- a/spec/lib/gitlab/diff/suggestions_parser_spec.rb
+++ b/spec/lib/gitlab/diff/suggestions_parser_spec.rb
@@ -69,5 +69,66 @@ def blob_lines_data(from_line, to_line)
                                                   lines_below: 0)
       end
     end
+
+    context 'multi-line suggestions' do
+      let(:markdown) do
+        <<-MARKDOWN.strip_heredoc
+          ```suggestion:-2+1
+            # above and below
+          ```
+
+          ```
+            nothing
+          ```
+
+          ```suggestion:-3
+            # only above
+          ```
+
+          ```suggestion:+3
+            # only below
+          ```
+
+          ```thing
+            this is not a suggestion, it's a thing
+          ```
+        MARKDOWN
+      end
+
+      it 'returns a list of Gitlab::Diff::Suggestion' do
+        expect(subject).to all(be_a(Gitlab::Diff::Suggestion))
+        expect(subject.size).to eq(3)
+      end
+
+      it 'suggestion with above and below param has correct data' do
+        from_line = position.new_line - 2
+        to_line = position.new_line + 1
+
+        expect(subject.first.to_hash).to include(from_content: blob_lines_data(from_line, to_line),
+                                                 to_content: "  # above and below\n",
+                                                 lines_above: 2,
+                                                 lines_below: 1)
+      end
+
+      it 'suggestion with above param has correct data' do
+        from_line = position.new_line - 3
+        to_line = position.new_line
+
+        expect(subject.second.to_hash).to eq(from_content: blob_lines_data(from_line, to_line),
+                                             to_content: "  # only above\n",
+                                             lines_above: 3,
+                                             lines_below: 0)
+      end
+
+      it 'suggestion with below param has correct data' do
+        from_line = position.new_line
+        to_line = position.new_line + 3
+
+        expect(subject.third.to_hash).to eq(from_content: blob_lines_data(from_line, to_line),
+                                            to_content: "  # only below\n",
+                                            lines_above: 0,
+                                            lines_below: 3)
+      end
+    end
   end
 end
diff --git a/spec/models/suggestion_spec.rb b/spec/models/suggestion_spec.rb
index cafc725dddb2ef414066f1ea94aa79541f3317fb..8d4e9070b19c8b885c5ea1013d6b606fa370a1d5 100644
--- a/spec/models/suggestion_spec.rb
+++ b/spec/models/suggestion_spec.rb
@@ -21,6 +21,22 @@
     end
   end
 
+  describe '#diff_lines' do
+    let(:suggestion) { create(:suggestion, :content_from_repo) }
+
+    it 'returns parsed diff lines' do
+      expected_diff_lines = Gitlab::Diff::SuggestionDiff.new(suggestion).diff_lines
+      diff_lines = suggestion.diff_lines
+
+      expect(diff_lines.size).to eq(expected_diff_lines.size)
+      expect(diff_lines).to all(be_a(Gitlab::Diff::Line))
+
+      expected_diff_lines.each_with_index do |expected_line, index|
+        expect(diff_lines[index].to_hash).to eq(expected_line.to_hash)
+      end
+    end
+  end
+
   describe '#appliable?' do
     context 'when note does not support suggestions' do
       it 'returns false' do
diff --git a/spec/serializers/suggestion_entity_spec.rb b/spec/serializers/suggestion_entity_spec.rb
index d38fc2b132b44cf9e2c96235bb27cd57685b76bf..d282a7f9c7abac2317a915998561d5e6417a9390 100644
--- a/spec/serializers/suggestion_entity_spec.rb
+++ b/spec/serializers/suggestion_entity_spec.rb
@@ -13,8 +13,7 @@
   subject { entity.as_json }
 
   it 'exposes correct attributes' do
-    expect(subject).to include(:id, :from_line, :to_line, :appliable,
-                               :applied, :from_content, :to_content)
+    expect(subject.keys).to match_array([:id, :appliable, :applied, :diff_lines, :current_user])
   end
 
   it 'exposes current user abilities' do
diff --git a/spec/services/preview_markdown_service_spec.rb b/spec/services/preview_markdown_service_spec.rb
index 85515d548a73e10b968698661ff9ddb8022dd7ec..a1d31464e07e5ace5917a818a4b62c10a7b298c4 100644
--- a/spec/services/preview_markdown_service_spec.rb
+++ b/spec/services/preview_markdown_service_spec.rb
@@ -2,7 +2,7 @@
 
 describe PreviewMarkdownService do
   let(:user) { create(:user) }
-  let(:project) { create(:project) }
+  let(:project) { create(:project, :repository) }
 
   before do
     project.add_developer(user)
@@ -20,23 +20,72 @@
   end
 
   describe 'suggestions' do
-    let(:params) { { text: "```suggestion\nfoo\n```", preview_suggestions: preview_suggestions } }
+    let(:merge_request) do
+      create(:merge_request, target_project: project, source_project: project)
+    end
+    let(:text) { "```suggestion\nfoo\n```" }
+    let(:params) do
+      suggestion_params.merge(text: text,
+                              target_type: 'MergeRequest',
+                              target_id: merge_request.iid)
+    end
     let(:service) { described_class.new(project, user, params) }
 
     context 'when preview markdown param is present' do
-      let(:preview_suggestions) { true }
+      let(:path) { "files/ruby/popen.rb" }
+      let(:line) { 10 }
+      let(:diff_refs) { merge_request.diff_refs }
+
+      let(:suggestion_params) do
+        {
+          preview_suggestions: true,
+          file_path: path,
+          line: line,
+          base_sha: diff_refs.base_sha,
+          start_sha: diff_refs.start_sha,
+          head_sha: diff_refs.head_sha
+        }
+      end
+
+      it 'returns suggestions referenced in text' do
+        position = Gitlab::Diff::Position.new(new_path: path,
+                                              new_line: line,
+                                              diff_refs: diff_refs)
+
+        expect(Gitlab::Diff::SuggestionsParser)
+          .to receive(:parse)
+          .with(text, position: position, project: merge_request.project)
+          .and_call_original
 
-      it 'returns users referenced in text' do
         result = service.execute
 
-        expect(result[:suggestions]).to eq(['foo'])
+        expect(result[:suggestions]).to all(be_a(Gitlab::Diff::Suggestion))
+      end
+
+      context 'when user is not authorized' do
+        let(:another_user) { create(:user) }
+        let(:service) { described_class.new(project, another_user, params) }
+
+        before do
+          project.add_guest(another_user)
+        end
+
+        it 'returns no suggestions' do
+          result = service.execute
+
+          expect(result[:suggestions]).to be_empty
+        end
       end
     end
 
     context 'when preview markdown param is not present' do
-      let(:preview_suggestions) { false }
+      let(:suggestion_params) do
+        {
+          preview_suggestions: false
+        }
+      end
 
-      it 'returns users referenced in text' do
+      it 'returns suggestions referenced in text' do
         result = service.execute
 
         expect(result[:suggestions]).to eq([])
@@ -49,8 +98,8 @@
     let(:params) do
       {
         text: "Please do it\n/assign #{user.to_reference}",
-        quick_actions_target_type: 'Issue',
-        quick_actions_target_id: issue.id
+        target_type: 'Issue',
+        target_id: issue.id
       }
     end
     let(:service) { described_class.new(project, user, params) }
@@ -72,7 +121,7 @@
     let(:params) do
       {
         text: "My work\n/estimate 2y",
-        quick_actions_target_type: 'MergeRequest'
+        target_type: 'MergeRequest'
       }
     end
     let(:service) { described_class.new(project, user, params) }
@@ -96,8 +145,8 @@
     let(:params) do
       {
         text: "My work\n/tag v1.2.3 Stable release",
-        quick_actions_target_type: 'Commit',
-        quick_actions_target_id: commit.id
+        target_type: 'Commit',
+        target_id: commit.id
       }
     end
     let(:service) { described_class.new(project, user, params) }
diff --git a/spec/services/suggestions/apply_service_spec.rb b/spec/services/suggestions/apply_service_spec.rb
index 80b5dcac6c77298736e7363719e36633213f47ce..7732767137c809fc57924fa92d096d2ae3f2f6f2 100644
--- a/spec/services/suggestions/apply_service_spec.rb
+++ b/spec/services/suggestions/apply_service_spec.rb
@@ -51,6 +51,10 @@ def apply(suggestion)
                                diff_refs: merge_request.diff_refs)
   end
 
+  let(:diff_note) do
+    create(:diff_note_on_merge_request, noteable: merge_request, position: position, project: project)
+  end
+
   let(:suggestion) do
     create(:suggestion, :content_from_repo, note: diff_note,
                                             to_content: "      raise RuntimeError, 'Explosion'\n      # explosion?\n")
@@ -108,12 +112,6 @@ def popen(cmd, path=nil)
                                target_project: project)
       end
 
-      let!(:diff_note) do
-        create(:diff_note_on_merge_request, noteable: merge_request,
-                                            position: position,
-                                            project: project)
-      end
-
       before do
         project.add_maintainer(user)
       end
@@ -192,11 +190,6 @@ def popen(cmd, path=nil)
           CONTENT
         end
 
-        let(:merge_request) do
-          create(:merge_request, source_project: project,
-                                 target_project: project)
-        end
-
         def create_suggestion(diff, old_line: nil, new_line: nil, from_content:, to_content:, path:)
           position = Gitlab::Diff::Position.new(old_path: path,
                                                 new_path: path,
@@ -291,6 +284,55 @@ def fetch_raw_diff(suggestion)
           expect(suggestion_2_diff.strip).to eq(expected_suggestion_2_diff.strip)
         end
       end
+
+      context 'multi-line suggestion' do
+        let(:expected_content) do
+          <<~CONTENT
+            require 'fileutils'
+            require 'open3'
+
+            module Popen
+              extend self
+
+            # multi
+            # line
+
+                vars = {
+                  "PWD" => path
+                }
+
+                options = {
+                  chdir: path
+                }
+
+                unless File.directory?(path)
+                  FileUtils.mkdir_p(path)
+                end
+
+                @cmd_output = ""
+                @cmd_status = 0
+
+                Open3.popen3(vars, *cmd, options) do |stdin, stdout, stderr, wait_thr|
+                  @cmd_output << stdout.read
+                  @cmd_output << stderr.read
+                  @cmd_status = wait_thr.value.exitstatus
+                end
+
+                return @cmd_output, @cmd_status
+              end
+            end
+          CONTENT
+        end
+
+        let(:suggestion) do
+          create(:suggestion, :content_from_repo, note: diff_note,
+                                                  lines_above: 2,
+                                                  lines_below: 3,
+                                                  to_content: "# multi\n# line\n")
+        end
+
+        it_behaves_like 'successfully creates commit and updates suggestion'
+      end
     end
 
     context 'fork-project' do