Merge branch 'autocomplete-space-prefix' into 'master'

Allow GFM autocomplete to be trigger without the preceding space

## What does this MR do?

Gives the ability to GFM autocomplete to be trigger even if there is no preceding space.

I've taken the regex from the at.js plugin & tweaked it to allow the leading character to be a special character.

## What are the relevant issue numbers?

Closes #19975 

## Screenshots (if relevant)

![Screen_Shot_2016-07-21_at_14.41.34](/uploads/19684ba286baeedb754e7457945480a8/Screen_Shot_2016-07-21_at_14.41.34.png)![Screen_Shot_2016-07-21_at_14.41.40](/uploads/a77349bce599ae93b4bcddd355087f5c/Screen_Shot_2016-07-21_at_14.41.40.png)![Screen_Shot_2016-07-21_at_14.41.46](/uploads/c35df17b678b24b73c94b181f0784188/Screen_Shot_2016-07-21_at_14.41.46.png)

See merge request !5395

app/assets/javascripts/gfm_auto_complete.js.es6

@@ -53,6 +53,26 @@
         } else {
           return value;
         }
+      },
+      matcher: function (flag, subtext) {
+        // The below is taken from At.js source
+        // Tweaked to commands to start without a space only if char before is a non-word character
+        // https://github.com/ichord/At.js
+        var _a, _y, regexp, match;
+        flag = flag.replace(/[\-\[\]\/\{\}\(\)\*\+\?\.\\\^\$\|]/g, "\\$&");
+
+        _a = decodeURI("%C3%80");
+        _y = decodeURI("%C3%BF");
+
+        regexp = new RegExp("(?:\\B|\\W|\\s)" + flag + "([A-Za-z" + _a + "-" + _y + "0-9_\'\.\+\-]*)|([^\\x00-\\xff]*)$", 'gi');
+
+        match = regexp.exec(subtext);
+
+        if (match) {
+          return match[2] || match[1];
+        } else {
+          return null;
+        }
       }
     },
     setup: _.debounce(function(input) {
@@ -91,10 +111,12 @@
         })(this),
         insertTpl: ':${name}:',
         data: ['loading'],
+        startWithSpace: false,
         callbacks: {
           sorter: this.DefaultOptions.sorter,
           filter: this.DefaultOptions.filter,
-          beforeInsert: this.DefaultOptions.beforeInsert
+          beforeInsert: this.DefaultOptions.beforeInsert,
+          matcher: this.DefaultOptions.matcher
         }
       });
       // Team Members
@@ -112,11 +134,13 @@
         insertTpl: '${atwho-at}${username}',
         searchKey: 'search',
         data: ['loading'],
+        startWithSpace: false,
         alwaysHighlightFirst: true,
         callbacks: {
           sorter: this.DefaultOptions.sorter,
           filter: this.DefaultOptions.filter,
           beforeInsert: this.DefaultOptions.beforeInsert,
+          matcher: this.DefaultOptions.matcher,
           beforeSave: function(members) {
             return $.map(members, function(m) {
               let title = '';
@@ -157,10 +181,12 @@
         })(this),
         data: ['loading'],
         insertTpl: '${atwho-at}${id}',
+        startWithSpace: false,
         callbacks: {
           sorter: this.DefaultOptions.sorter,
           filter: this.DefaultOptions.filter,
           beforeInsert: this.DefaultOptions.beforeInsert,
+          matcher: this.DefaultOptions.matcher,
           beforeSave: function(issues) {
             return $.map(issues, function(i) {
               if (i.title == null) {
@@ -190,7 +216,9 @@
         })(this),
         insertTpl: '${atwho-at}"${title}"',
         data: ['loading'],
+        startWithSpace: false,
         callbacks: {
+          matcher: this.DefaultOptions.matcher,
           sorter: this.DefaultOptions.sorter,
           beforeSave: function(milestones) {
             return $.map(milestones, function(m) {
@@ -220,11 +248,13 @@
           };
         })(this),
         data: ['loading'],
+        startWithSpace: false,
         insertTpl: '${atwho-at}${id}',
         callbacks: {
           sorter: this.DefaultOptions.sorter,
           filter: this.DefaultOptions.filter,
           beforeInsert: this.DefaultOptions.beforeInsert,
+          matcher: this.DefaultOptions.matcher,
           beforeSave: function(merges) {
             return $.map(merges, function(m) {
               if (m.title == null) {
@@ -245,7 +275,9 @@
         searchKey: 'search',
         displayTpl: this.Labels.template,
         insertTpl: '${atwho-at}${title}',
+        startWithSpace: false,
         callbacks: {
+          matcher: this.DefaultOptions.matcher,
           sorter: this.DefaultOptions.sorter,
           beforeSave: function(merges) {
             var sanitizeLabelTitle;

spec/features/issues/gfm_autocomplete_spec.rb

+require 'rails_helper'
+
+feature 'GFM autocomplete', feature: true, js: true do
+  include WaitForAjax
+  let(:user)    { create(:user) }
+  let(:project) { create(:project) }
+  let(:issue)   { create(:issue, project: project) }
+
+  before do
+    project.team << [user, :master]
+    login_as(user)
+    visit namespace_project_issue_path(project.namespace, project, issue)
+
+    wait_for_ajax
+  end
+
+  it 'opens autocomplete menu when field starts with text' do
+    page.within '.timeline-content-form' do
+      find('#note_note').native.send_keys('')
+      find('#note_note').native.send_keys('@')
+    end
+
+    expect(page).to have_selector('.atwho-container')
+  end
+
+  it 'opens autocomplete menu when field is prefixed with non-text character' do
+    page.within '.timeline-content-form' do
+      find('#note_note').native.send_keys('')
+      find('#note_note').native.send_keys('@')
+    end
+
+    expect(page).to have_selector('.atwho-container')
+  end
+
+  it 'doesnt open autocomplete menu character is prefixed with text' do
+    page.within '.timeline-content-form' do
+      find('#note_note').native.send_keys('testing')
+      find('#note_note').native.send_keys('@')
+    end
+
+    expect(page).not_to have_selector('.atwho-view')
+  end
+end