Merge branch 'search-helper-escape-regexp' into 'master'

Escape search terms before passing to Regexp

## What does this MR do?

Use `Regexp.escape` to escape the search terms before passing them to `Regexp.new`.

## Why was this MR needed?

- evaluated regular expressions in search terms lead to unexpected result
- unbalanced parentheses in search term lead to server error 

## TODO

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added

## What are the relevant issue numbers?

fixes #14360

See merge request !6241

CHANGELOG

@@ -12,6 +12,7 @@ v 8.12.0 (unreleased)
   - Change logo animation to CSS (ClemMakesApps)
   - Instructions for enabling Git packfile bitmaps !6104
   - Fix pagination on user snippets page
+  - Escape search term before passing it to Regexp.new !6241 (winniehell)
   - Change merge_error column from string to text type
   - Reduce contributions calendar data payload (ClemMakesApps)
   - Add `web_url` field to issue, merge request, and snippet API objects (Ben Boeckel)

app/helpers/search_helper.rb

@@ -7,8 +7,10 @@ module SearchHelper
       projects_autocomplete(term)
     ].flatten
 
+    search_pattern = Regexp.new(Regexp.escape(term), "i")
+
     generic_results = project_autocomplete + default_autocomplete + help_autocomplete
-    generic_results.select! { |result| result[:label] =~ Regexp.new(term, "i") }
+    generic_results.select! { |result| result[:label] =~ search_pattern }
 
     [
       resources_results,

spec/helpers/search_helper_spec.rb

@@ -32,6 +32,10 @@ describe SearchHelper do
         expect(search_autocomplete_opts("adm").size).to eq(1)
       end
 
+      it "does not allow regular expression in search term" do
+        expect(search_autocomplete_opts("(webhooks|api)").size).to eq(0)
+      end
+
       it "includes the user's groups" do
         create(:group).add_owner(user)
         expect(search_autocomplete_opts("gro").size).to eq(1)