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

1 files changed, 16 insertions, 6 deletions

diff --git a/spec/lib/gitlab/sql/union_spec.rb b/spec/lib/gitlab/sql/union_spec.rb
index 0cdbab87544..849edb09476 100644
--- a/spec/lib/gitlab/sql/union_spec.rb
+++ b/spec/lib/gitlab/sql/union_spec.rb
@@ -1,16 +1,26 @@
 require 'spec_helper'
 
 describe Gitlab::SQL::Union, lib: true do
+  let(:relation_1) { User.where(email: 'alice@example.com').select(:id) }
+  let(:relation_2) { User.where(email: 'bob@example.com').select(:id) }
+
+  def to_sql(relation)
+    relation.reorder(nil).to_sql
+  end
+
   describe '#to_sql' do
     it 'returns a String joining relations together using a UNION' do
-      rel1  = User.where(email: 'alice@example.com')
-      rel2  = User.where(email: 'bob@example.com')
-      union = described_class.new([rel1, rel2])
+      union = described_class.new([relation_1, relation_2])
+
+      expect(union.to_sql).to eq("#{to_sql(relation_1)}\nUNION\n#{to_sql(relation_2)}")
+    end
 
-      sql1 = rel1.reorder(nil).to_sql
-      sql2 = rel2.reorder(nil).to_sql
+    it 'skips Model.none segements' do
+      empty_relation = User.none
+      union = described_class.new([empty_relation, relation_1, relation_2])
 
-      expect(union.to_sql).to eq("#{sql1}\nUNION\n#{sql2}")
+      expect{User.where("users.id IN (#{union.to_sql})").to_a}.not_to raise_error
+      expect(union.to_sql).to eq("#{to_sql(relation_1)}\nUNION\n#{to_sql(relation_2)}")
     end
   end
 end