Merge branch 'jej-note-search-uses-finder' into 'security'

Fix missing Note access checks in by moving Note#search to updated NoteFinder

Split from !2024 to partially solve https://gitlab.com/gitlab-org/gitlab-ce/issues/23867

## Which fixes are in this MR?

:warning: - Potentially untested  
:bomb: - No test coverage  
:traffic_light: - Test coverage of some sort exists (a test failed when error raised)  
:vertical_traffic_light: - Test coverage of return value (a test failed when nil used)  
:white_check_mark: - Permissions check tested

### Note lookup without access check

- [x] :white_check_mark: app/finders/notes_finder.rb:13 :download_code check
- [x] :white_check_mark: app/finders/notes_finder.rb:19 `SnippetsFinder`
- [x] :white_check_mark: app/models/note.rb:121 [`Issue#visible_to_user`]
- [x] :white_check_mark: lib/gitlab/project_search_results.rb:113
  - This is the only use of `app/models/note.rb:121` above, but importantly has no access checks at all. This means it leaks MR comments and snippets when those features are `team-only` in addition to the issue comments which would be fixed by `app/models/note.rb:121`.
  - It is only called from SearchController where `can?(current_user, :download_code, @project)` is checked, so commit comments are not leaked.

### Previous discussions
- [x] https://dev.gitlab.org/gitlab/gitlabhq/merge_requests/2024/diffs#b915c5267a63628b0bafd23d37792ae73ceae272_13_13 `: download_code` check on commit
- [x] https://dev.gitlab.org/gitlab/gitlabhq/merge_requests/2024/diffs#b915c5267a63628b0bafd23d37792ae73ceae272_19_19 `SnippetsFinder` should be used
  - `SnippetsFinder` should check if the snippets feature is enabled -> https://gitlab.com/gitlab-org/gitlab-ce/issues/25223

###  Acceptance criteria met?
- [x] Tests added for new code
- [x] TODO comments removed
- [x] Squashed and removed skipped tests
- [x] Changelog entry
- [ ] State Gitlab versions affected and issue severity in description
- [ ] Create technical debt issue for NotesFinder.
  - Either split into `NotesFinder::ForTarget` and `NotesFinder::Search` or consider object per notable type such as `NotesFinder::OnIssue`. For the first option could create `NotesFinder::Base` which is either inherited from or which can be included in the other two.
  - Avoid case statement anti-pattern in this finder with use of `NotesFinder::OnCommit` etc. Consider something on the finder for this? `Model.finder(user, project)`
  - Move `inc_author` to the controller, and implement `related_notes` to replace `non_diff_notes`/`mr_and_commit_notes`

See merge request !2035

2 files changed, 2 insertions, 19 deletions

diff --git a/app/models/merge_request.rb b/app/models/merge_request.rb
index ea3cf1cdaac..b73d7acefea 100644
--- a/app/models/merge_request.rb
+++ b/app/models/merge_request.rb
@@ -452,7 +452,7 @@ class MergeRequest < ActiveRecord::Base
     should_remove_source_branch? || force_remove_source_branch?
   end
 
-  def mr_and_commit_notes
+  def related_notes
     # Fetch comments only from last 100 commits
     commits_for_notes_limit = 100
     commit_ids = commits.last(commits_for_notes_limit).map(&:id)
@@ -468,7 +468,7 @@ class MergeRequest < ActiveRecord::Base
   end
 
   def discussions
-    @discussions ||= self.mr_and_commit_notes.
+    @discussions ||= self.related_notes.
       inc_relations_for_view.
       fresh.
       discussions
diff --git a/app/models/note.rb b/app/models/note.rb
index 08bd08743ef..0c1b05dabf2 100644
--- a/app/models/note.rb
+++ b/app/models/note.rb
@@ -107,23 +107,6 @@ class Note < ActiveRecord::Base
       Discussion.for_diff_notes(active_notes).
         map { |d| [d.line_code, d] }.to_h
     end
-
-    # Searches for notes matching the given query.
-    #
-    # This method uses ILIKE on PostgreSQL and LIKE on MySQL.
-    #
-    # query   - The search query as a String.
-    # as_user - Limit results to those viewable by a specific user
-    #
-    # Returns an ActiveRecord::Relation.
-    def search(query, as_user: nil)
-      table   = arel_table
-      pattern = "%#{query}%"
-
-      Note.joins('LEFT JOIN issues ON issues.id = noteable_id').
-        where(table[:note].matches(pattern)).
-        merge(Issue.visible_to_user(as_user))
-    end
   end
 
   def cross_reference?