Fixes diff sugestions removing dashes from diff

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/55634

app/assets/javascripts/vue_shared/components/markdown/field.vue

@@ -89,7 +89,6 @@ export default {
       return this.referencedUsers.length >= referencedUsersThreshold;
     },
     lineContent() {
-      const FIRST_CHAR_REGEX = /^(\+|-)/;
       const [firstSuggestion] = this.suggestions;
       if (firstSuggestion) {
         return firstSuggestion.from_content;
@@ -99,7 +98,7 @@ export default {
         const { rich_text: richText, text } = this.line;
         if (text) {
-          return text.replace(FIRST_CHAR_REGEX, '');
+          return text;
         }
         return _.unescape(stripHtml(richText).replace(/\n/g, ''));

app/assets/javascripts/vue_shared/components/markdown/suggestions.vue

@@ -82,13 +82,12 @@ export default {
       // 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 = `${line.innerText.replace(FIRST_CHAR_REGEX, '')}\n`;
+        const content = `${line.innerText}\n`;
         const lineNumber = fromLine + i;
         lines.push({ content, lineNumber });
       });

changelogs/unreleased/suggestion-dashes.yml

+---
+title: Fixed diff suggestions removing dashes
+merge_request:
+author:
+type: fixed

spec/javascripts/vue_shared/components/markdown/suggestions_spec.js

@@ -29,7 +29,7 @@ const generateLine = content => {
 const generateMockLines = () => {
   const line1 = generateLine('Line 1');
   const line2 = generateLine('Line 2');
-  const line3 = generateLine('Line 3');
+  const line3 = generateLine('- Line 3');
   const container = document.createElement('div');
   container.appendChild(line1);
@@ -80,7 +80,7 @@ describe('Suggestion component', () => {
       const expectedReturn = [
         { content: 'Line 1\n', lineNumber: 1 },
         { content: 'Line 2\n', lineNumber: 2 },
-        { content: 'Line 3\n', lineNumber: 3 },
+        { content: '- Line 3\n', lineNumber: 3 },
       ];
       expect(vm.extractNewLines(generateMockLines())).toEqual(expectedReturn);