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

16 files changed, 387 insertions, 121 deletions

diff --git a/app/controllers/projects/notes_controller.rb b/app/controllers/projects/notes_controller.rb
index f029fde2a2f..3c4e109f7a2 100644
--- a/app/controllers/projects/notes_controller.rb
+++ b/app/controllers/projects/notes_controller.rb
@@ -216,6 +216,6 @@ class Projects::NotesController < Projects::ApplicationController
   end
 
   def find_current_user_notes
-    @notes = NotesFinder.new.execute(project, current_user, params)
+    @notes = NotesFinder.new(project, current_user, params).execute.inc_author
   end
 end
diff --git a/app/finders/notes_finder.rb b/app/finders/notes_finder.rb
index 2484339e3a4..4bd8c83081a 100644
--- a/app/finders/notes_finder.rb
+++ b/app/finders/notes_finder.rb
@@ -1,27 +1,102 @@
 class NotesFinder
   FETCH_OVERLAP = 5.seconds
 
-  def execute(project, current_user, params)
-    target_type = params[:target_type]
-    target_id   = params[:target_id]
-    # Default to 0 to remain compatible with old clients
-    last_fetched_at = Time.at(params.fetch(:last_fetched_at, 0).to_i)
-
-    notes =
-      case target_type
-      when "commit"
-        project.notes.for_commit_id(target_id).non_diff_notes
-      when "issue"
-        IssuesFinder.new(current_user, project_id: project.id).find(target_id).notes.inc_author
-      when "merge_request"
-        MergeRequestsFinder.new(current_user, project_id: project.id).find(target_id).mr_and_commit_notes.inc_author
-      when "snippet", "project_snippet"
-        project.snippets.find(target_id).notes
+  # Used to filter Notes
+  # When used with target_type and target_id this returns notes specifically for the controller
+  #
+  # Arguments:
+  #   current_user - which user check authorizations with
+  #   project - which project to look for notes on
+  #   params:
+  #     target_type: string
+  #     target_id: integer
+  #     last_fetched_at: time
+  #     search: string
+  #
+  def initialize(project, current_user, params = {})
+    @project = project
+    @current_user = current_user
+    @params = params
+    init_collection
+  end
+
+  def execute
+    @notes = since_fetch_at(@params[:last_fetched_at]) if @params[:last_fetched_at]
+    @notes
+  end
+
+  private
+
+  def init_collection
+    if @params[:target_id]
+      @notes = on_target(@params[:target_type], @params[:target_id])
+    else
+      @notes = notes_of_any_type
+    end
+  end
+
+  def notes_of_any_type
+    types = %w(commit issue merge_request snippet)
+    note_relations = types.map { |t| notes_for_type(t) }
+    note_relations.map!{ |notes| search(@params[:search], notes) } if @params[:search]
+    UnionFinder.new.find_union(note_relations, Note)
+  end
+
+  def noteables_for_type(noteable_type)
+    case noteable_type
+    when "issue"
+      IssuesFinder.new(@current_user, project_id: @project.id).execute
+    when "merge_request"
+      MergeRequestsFinder.new(@current_user, project_id: @project.id).execute
+    when "snippet", "project_snippet"
+      SnippetsFinder.new.execute(@current_user, filter: :by_project, project: @project)
+    else
+      raise 'invalid target_type'
+    end
+  end
+
+  def notes_for_type(noteable_type)
+    if noteable_type == "commit"
+      if Ability.allowed?(@current_user, :download_code, @project)
+        @project.notes.where(noteable_type: 'Commit')
+      else
+        Note.none
+      end
+    else
+      finder = noteables_for_type(noteable_type)
+      @project.notes.where(noteable_type: finder.base_class.name, noteable_id: finder.reorder(nil))
+    end
+  end
+
+  def on_target(target_type, target_id)
+    if target_type == "commit"
+      notes_for_type('commit').for_commit_id(target_id)
+    else
+      target = noteables_for_type(target_type).find(target_id)
+
+      if target.respond_to?(:related_notes)
+        target.related_notes
       else
-        raise 'invalid target_type'
+        target.notes
       end
+    end
+  end
+
+  # Searches for notes matching the given query.
+  #
+  # This method uses ILIKE on PostgreSQL and LIKE on MySQL.
+  #
+  def search(query, notes_relation = @notes)
+    pattern = "%#{query}%"
+    notes_relation.where(Note.arel_table[:note].matches(pattern))
+  end
+
+  # Notes changed since last fetch
+  # Uses overlapping intervals to avoid worrying about race conditions
+  def since_fetch_at(fetch_time)
+    # Default to 0 to remain compatible with old clients
+    last_fetched_at = Time.at(@params.fetch(:last_fetched_at, 0).to_i)
 
-    # Use overlapping intervals to avoid worrying about race conditions
-    notes.where('updated_at > ?', last_fetched_at - FETCH_OVERLAP).fresh
+    @notes.where('updated_at > ?', last_fetched_at - FETCH_OVERLAP).fresh
   end
 end
diff --git a/app/models/merge_request.rb b/app/models/merge_request.rb
index 7fc3b6671d9..6a10deab688 100644
--- a/app/models/merge_request.rb
+++ b/app/models/merge_request.rb
@@ -453,7 +453,7 @@ 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)
@@ -469,7 +469,7 @@ 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 9881506edc8..10ae480a44f 100644
--- a/app/models/note.rb
+++ b/app/models/note.rb
@@ -104,23 +104,6 @@ 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?
diff --git a/app/views/projects/merge_requests/_merge_request.html.haml b/app/views/projects/merge_requests/_merge_request.html.haml
index 9ffcc48eb80..1cde318bbae 100644
--- a/app/views/projects/merge_requests/_merge_request.html.haml
+++ b/app/views/projects/merge_requests/_merge_request.html.haml
@@ -39,7 +39,7 @@
           = icon('thumbs-down')
           = downvotes
 
-      - note_count = merge_request.mr_and_commit_notes.user.count
+      - note_count = merge_request.related_notes.user.count
       %li
         = link_to merge_request_path(merge_request, anchor: 'notes'), class: ('no-comments' if note_count.zero?) do
           = icon('comments')
diff --git a/app/views/projects/merge_requests/_show.html.haml b/app/views/projects/merge_requests/_show.html.haml
index 0e2975bd551..306c754215a 100644
--- a/app/views/projects/merge_requests/_show.html.haml
+++ b/app/views/projects/merge_requests/_show.html.haml
@@ -53,7 +53,7 @@
             %li.notes-tab
               = link_to namespace_project_merge_request_path(@project.namespace, @project, @merge_request), data: { target: 'div#notes', action: 'notes', toggle: 'tab' } do
                 Discussion
-                %span.badge= @merge_request.mr_and_commit_notes.user.count
+                %span.badge= @merge_request.related_notes.user.count
             - if @merge_request.source_project
               %li.commits-tab
                 = link_to commits_namespace_project_merge_request_path(@project.namespace, @project, @merge_request), data: { target: 'div#commits', action: 'commits', toggle: 'tab' } do
diff --git a/changelogs/unreleased/jej-note-search-uses-finder.yml b/changelogs/unreleased/jej-note-search-uses-finder.yml
new file mode 100644
index 00000000000..1768bdfd487
--- /dev/null
+++ b/changelogs/unreleased/jej-note-search-uses-finder.yml
@@ -0,0 +1,4 @@
+---
+title: Fix missing Note access checks by moving Note#search to updated NoteFinder
+merge_request: 
+author: 
diff --git a/lib/gitlab/project_search_results.rb b/lib/gitlab/project_search_results.rb
index 66e6b29e798..6bdf3db9cb8 100644
--- a/lib/gitlab/project_search_results.rb
+++ b/lib/gitlab/project_search_results.rb
@@ -110,7 +110,7 @@ module Gitlab
     end
 
     def notes
-      @notes ||= project.notes.user.search(query, as_user: @current_user).order('updated_at DESC')
+      @notes ||= NotesFinder.new(project, @current_user, search: query).execute.user.order('updated_at DESC')
     end
 
     def commits
diff --git a/lib/gitlab/sql/union.rb b/lib/gitlab/sql/union.rb
index 1cd89b3a9c4..222021e8802 100644
--- a/lib/gitlab/sql/union.rb
+++ b/lib/gitlab/sql/union.rb
@@ -22,9 +22,7 @@ module Gitlab
         # By using "unprepared_statements" we remove the usage of placeholders
         # (thus fixing this problem), at a slight performance cost.
         fragments = ActiveRecord::Base.connection.unprepared_statement do
-          @relations.map do |rel|
-            rel.reorder(nil).to_sql
-          end
+          @relations.map { |rel| rel.reorder(nil).to_sql }.reject(&:blank?)
         end
 
         fragments.join("\nUNION\n")
diff --git a/spec/controllers/search_controller_spec.rb b/spec/controllers/search_controller_spec.rb
new file mode 100644
index 00000000000..b7bb9290712
--- /dev/null
+++ b/spec/controllers/search_controller_spec.rb
@@ -0,0 +1,61 @@
+require 'spec_helper'
+
+describe SearchController do
+  let(:user)    { create(:user) }
+  let(:project) { create(:empty_project, :public) }
+
+  before do
+    sign_in(user)
+  end
+
+  it 'finds issue comments' do
+    project = create(:empty_project, :public)
+    note = create(:note_on_issue, project: project)
+
+    get :show, project_id: project.id, scope: 'notes', search: note.note
+
+    expect(assigns[:search_objects].first).to eq note
+  end
+
+  context 'on restricted projects' do
+    context 'when signed out' do
+      before { sign_out(user) }
+
+      it "doesn't expose comments on issues" do
+        project = create(:empty_project, :public, issues_access_level: ProjectFeature::PRIVATE)
+        note = create(:note_on_issue, project: project)
+
+        get :show, project_id: project.id, scope: 'notes', search: note.note
+
+        expect(assigns[:search_objects].count).to eq(0)
+      end
+    end
+
+    it "doesn't expose comments on issues" do
+      project = create(:empty_project, :public, issues_access_level: ProjectFeature::PRIVATE)
+      note = create(:note_on_issue, project: project)
+
+      get :show, project_id: project.id, scope: 'notes', search: note.note
+
+      expect(assigns[:search_objects].count).to eq(0)
+    end
+
+    it "doesn't expose comments on merge_requests" do
+      project = create(:empty_project, :public, merge_requests_access_level: ProjectFeature::PRIVATE)
+      note = create(:note_on_merge_request, project: project)
+
+      get :show, project_id: project.id, scope: 'notes', search: note.note
+
+      expect(assigns[:search_objects].count).to eq(0)
+    end
+
+    it "doesn't expose comments on snippets" do
+      project = create(:empty_project, :public, snippets_access_level: ProjectFeature::PRIVATE)
+      note = create(:note_on_project_snippet, project: project)
+
+      get :show, project_id: project.id, scope: 'notes', search: note.note
+
+      expect(assigns[:search_objects].count).to eq(0)
+    end
+  end
+end
diff --git a/spec/factories/notes.rb b/spec/factories/notes.rb
index 6919002dedc..a10ba629760 100644
--- a/spec/factories/notes.rb
+++ b/spec/factories/notes.rb
@@ -67,7 +67,7 @@ FactoryGirl.define do
     end
 
     trait :on_project_snippet do
-      noteable { create(:snippet, project: project) }
+      noteable { create(:project_snippet, project: project) }
     end
 
     trait :system do
diff --git a/spec/finders/notes_finder_spec.rb b/spec/finders/notes_finder_spec.rb
index 7c6860372cc..4d21254323c 100644
--- a/spec/finders/notes_finder_spec.rb
+++ b/spec/finders/notes_finder_spec.rb
@@ -2,59 +2,203 @@ require 'spec_helper'
 
 describe NotesFinder do
   let(:user) { create :user }
-  let(:project) { create :project }
-  let(:note1) { create :note_on_commit, project: project }
-  let(:note2) { create :note_on_commit, project: project }
-  let(:commit) { note1.noteable }
+  let(:project) { create(:empty_project) }
 
   before do
     project.team << [user, :master]
   end
 
   describe '#execute' do
-    let(:params)  { { target_id: commit.id, target_type: 'commit', last_fetched_at: 1.hour.ago.to_i } }
+    it 'finds notes on snippets when project is public and user isnt a member'
 
-    before do
-      note1
-      note2
+    it 'finds notes on merge requests' do
+      create(:note_on_merge_request, project: project)
+
+      notes = described_class.new(project, user).execute
+
+      expect(notes.count).to eq(1)
     end
 
-    it 'finds all notes' do
-      notes = NotesFinder.new.execute(project, user, params)
-      expect(notes.size).to eq(2)
+    it 'finds notes on snippets' do
+      create(:note_on_project_snippet, project: project)
+
+      notes = described_class.new(project, user).execute
+
+      expect(notes.count).to eq(1)
     end
 
-    it 'raises an exception for an invalid target_type' do
-      params.merge!(target_type: 'invalid')
-      expect { NotesFinder.new.execute(project, user, params) }.to raise_error('invalid target_type')
+    it "excludes notes on commits the author can't download" do
+      project = create(:project, :private)
+      note = create(:note_on_commit, project: project)
+      params = { target_type: 'commit', target_id: note.noteable.id }
+
+      notes = described_class.new(project, create(:user), params).execute
+
+      expect(notes.count).to eq(0)
     end
 
-    it 'filters out old notes' do
-      note2.update_attribute(:updated_at, 2.hours.ago)
-      notes = NotesFinder.new.execute(project, user, params)
-      expect(notes).to eq([note1])
+    it 'succeeds when no notes found' do
+      notes = described_class.new(project, create(:user)).execute
+
+      expect(notes.count).to eq(0)
     end
 
-    context 'confidential issue notes' do
-      let(:confidential_issue) { create(:issue, :confidential, project: project, author: user) }
-      let!(:confidential_note) { create(:note, noteable: confidential_issue, project: confidential_issue.project) }
+    context 'on restricted projects' do
+      let(:project) do
+        create(:empty_project, :public, issues_access_level: ProjectFeature::PRIVATE,
+                                        snippets_access_level: ProjectFeature::PRIVATE,
+                                        merge_requests_access_level: ProjectFeature::PRIVATE)
+      end
+
+      it 'publicly excludes notes on merge requests' do
+        create(:note_on_merge_request, project: project)
+
+        notes = described_class.new(project, create(:user)).execute
+
+        expect(notes.count).to eq(0)
+      end
+
+      it 'publicly excludes notes on issues' do
+        create(:note_on_issue, project: project)
+
+        notes = described_class.new(project, create(:user)).execute
+
+        expect(notes.count).to eq(0)
+      end
+
+      it 'publicly excludes notes on snippets' do
+        create(:note_on_project_snippet, project: project)
+
+        notes = described_class.new(project, create(:user)).execute
+
+        expect(notes.count).to eq(0)
+      end
+    end
+
+    context 'for target' do
+      let(:project) { create(:project) }
+      let(:note1) { create :note_on_commit, project: project }
+      let(:note2) { create :note_on_commit, project: project }
+      let(:commit) { note1.noteable }
+      let(:params)  { { target_id: commit.id, target_type: 'commit', last_fetched_at: 1.hour.ago.to_i } }
+
+      before do
+        note1
+        note2
+      end
+
+      it 'finds all notes' do
+        notes = described_class.new(project, user, params).execute
+        expect(notes.size).to eq(2)
+      end
+
+      it 'finds notes on merge requests' do
+        note = create(:note_on_merge_request, project: project)
+        params = { target_type: 'merge_request', target_id: note.noteable.id }
+
+        notes = described_class.new(project, user, params).execute
+
+        expect(notes).to include(note)
+      end
+
+      it 'finds notes on snippets' do
+        note = create(:note_on_project_snippet, project: project)
+        params = { target_type: 'snippet', target_id: note.noteable.id }
 
-      let(:params) { { target_id: confidential_issue.id, target_type: 'issue', last_fetched_at: 1.hour.ago.to_i } }
+        notes = described_class.new(project, user, params).execute
 
-      it 'returns notes if user can see the issue' do
-        expect(NotesFinder.new.execute(project, user, params)).to eq([confidential_note])
+        expect(notes.count).to eq(1)
       end
 
-      it 'raises an error if user can not see the issue' do
+      it 'raises an exception for an invalid target_type' do
+        params.merge!(target_type: 'invalid')
+        expect { described_class.new(project, user, params).execute }.to raise_error('invalid target_type')
+      end
+
+      it 'filters out old notes' do
+        note2.update_attribute(:updated_at, 2.hours.ago)
+        notes = described_class.new(project, user, params).execute
+        expect(notes).to eq([note1])
+      end
+
+      context 'confidential issue notes' do
+        let(:confidential_issue) { create(:issue, :confidential, project: project, author: user) }
+        let!(:confidential_note) { create(:note, noteable: confidential_issue, project: confidential_issue.project) }
+
+        let(:params) { { target_id: confidential_issue.id, target_type: 'issue', last_fetched_at: 1.hour.ago.to_i } }
+
+        it 'returns notes if user can see the issue' do
+          expect(described_class.new(project, user, params).execute).to eq([confidential_note])
+        end
+
+        it 'raises an error if user can not see the issue' do
+          user = create(:user)
+          expect { described_class.new(project, user, params).execute }.to raise_error(ActiveRecord::RecordNotFound)
+        end
+
+        it 'raises an error for project members with guest role' do
+          user = create(:user)
+          project.team << [user, :guest]
+
+          expect { described_class.new(project, user, params).execute }.to raise_error(ActiveRecord::RecordNotFound)
+        end
+      end
+    end
+  end
+
+  describe '.search' do
+    let(:project) { create(:empty_project, :public) }
+    let(:note) { create(:note_on_issue, note: 'WoW', project: project) }
+
+    it 'returns notes with matching content' do
+      expect(described_class.new(note.project, nil, search: note.note).execute).to eq([note])
+    end
+
+    it 'returns notes with matching content regardless of the casing' do
+      expect(described_class.new(note.project, nil, search: 'WOW').execute).to eq([note])
+    end
+
+    it 'returns commit notes user can access' do
+      note = create(:note_on_commit, project: project)
+
+      expect(described_class.new(note.project, create(:user), search: note.note).execute).to eq([note])
+    end
+
+    context "confidential issues" do
+      let(:user) { create(:user) }
+      let(:confidential_issue) { create(:issue, :confidential, project: project, author: user) }
+      let(:confidential_note) { create(:note, note: "Random", noteable: confidential_issue, project: confidential_issue.project) }
+
+      it "returns notes with matching content if user can see the issue" do
+        expect(described_class.new(confidential_note.project, user, search: confidential_note.note).execute).to eq([confidential_note])
+      end
+
+      it "does not return notes with matching content if user can not see the issue" do
         user = create(:user)
-        expect { NotesFinder.new.execute(project, user, params) }.to raise_error(ActiveRecord::RecordNotFound)
+        expect(described_class.new(confidential_note.project, user, search: confidential_note.note).execute).to be_empty
       end
 
-      it 'raises an error for project members with guest role' do
+      it "does not return notes with matching content for project members with guest role" do
         user = create(:user)
         project.team << [user, :guest]
+        expect(described_class.new(confidential_note.project, user, search: confidential_note.note).execute).to be_empty
+      end
+
+      it "does not return notes with matching content for unauthenticated users" do
+        expect(described_class.new(confidential_note.project, nil, search: confidential_note.note).execute).to be_empty
+      end
+    end
+
+    context 'inlines SQL filters on subqueries for performance' do
+      let(:sql) { described_class.new(note.project, nil, search: note.note).execute.to_sql }
+      let(:number_of_noteable_types) { 4 }
+
+      specify 'project_id check' do
+        expect(sql.scan(/project_id/).count).to be >= (number_of_noteable_types + 2)
+      end
 
-        expect { NotesFinder.new.execute(project, user, params) }.to raise_error(ActiveRecord::RecordNotFound)
+      specify 'search filter' do
+        expect(sql.scan(/LIKE/).count).to be >= number_of_noteable_types
       end
     end
   end
diff --git a/spec/lib/gitlab/project_search_results_spec.rb b/spec/lib/gitlab/project_search_results_spec.rb
index 3cd9863ec6a..14ee386dba6 100644
--- a/spec/lib/gitlab/project_search_results_spec.rb
+++ b/spec/lib/gitlab/project_search_results_spec.rb
@@ -149,4 +149,33 @@ describe Gitlab::ProjectSearchResults, lib: true do
       expect(results.issues_count).to eq 3
     end
   end
+
+  describe 'notes search' do
+    it 'lists notes' do
+      project = create(:empty_project, :public)
+      note = create(:note, project: project)
+
+      results = described_class.new(user, project, note.note)
+
+      expect(results.objects('notes')).to include note
+    end
+
+    it "doesn't list issue notes when access is restricted" do
+      project = create(:empty_project, :public, issues_access_level: ProjectFeature::PRIVATE)
+      note = create(:note_on_issue, project: project)
+
+      results = described_class.new(user, project, note.note)
+
+      expect(results.objects('notes')).not_to include note
+    end
+
+    it "doesn't list merge_request notes when access is restricted" do
+      project = create(:empty_project, :public, merge_requests_access_level: ProjectFeature::PRIVATE)
+      note = create(:note_on_merge_request, project: project)
+
+      results = described_class.new(user, project, note.note)
+
+      expect(results.objects('notes')).not_to include note
+    end
+  end
 end
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
diff --git a/spec/models/merge_request_spec.rb b/spec/models/merge_request_spec.rb
index 58ccd056328..2eaea315bae 100644
--- a/spec/models/merge_request_spec.rb
+++ b/spec/models/merge_request_spec.rb
@@ -202,7 +202,7 @@ describe MergeRequest, models: true do
     end
   end
 
-  describe "#mr_and_commit_notes" do
+  describe "#related_notes" do
     let!(:merge_request) { create(:merge_request) }
 
     before do
@@ -214,7 +214,7 @@ describe MergeRequest, models: true do
 
     it "includes notes for commits" do
       expect(merge_request.commits).not_to be_empty
-      expect(merge_request.mr_and_commit_notes.count).to eq(2)
+      expect(merge_request.related_notes.count).to eq(2)
     end
 
     it "includes notes for commits from target project as well" do
@@ -222,7 +222,7 @@ describe MergeRequest, models: true do
                               project: merge_request.target_project)
 
       expect(merge_request.commits).not_to be_empty
-      expect(merge_request.mr_and_commit_notes.count).to eq(3)
+      expect(merge_request.related_notes.count).to eq(3)
     end
   end
 
diff --git a/spec/models/note_spec.rb b/spec/models/note_spec.rb
index 17a15b12dcb..310fecd8a5c 100644
--- a/spec/models/note_spec.rb
+++ b/spec/models/note_spec.rb
@@ -162,44 +162,6 @@ describe Note, models: true do
     end
   end
 
-  describe '.search' do
-    let(:note) { create(:note_on_issue, note: 'WoW') }
-
-    it 'returns notes with matching content' do
-      expect(described_class.search(note.note)).to eq([note])
-    end
-
-    it 'returns notes with matching content regardless of the casing' do
-      expect(described_class.search('WOW')).to eq([note])
-    end
-
-    context "confidential issues" do
-      let(:user) { create(:user) }
-      let(:project) { create(:project) }
-      let(:confidential_issue) { create(:issue, :confidential, project: project, author: user) }
-      let(:confidential_note) { create(:note, note: "Random", noteable: confidential_issue, project: confidential_issue.project) }
-
-      it "returns notes with matching content if user can see the issue" do
-        expect(described_class.search(confidential_note.note, as_user: user)).to eq([confidential_note])
-      end
-
-      it "does not return notes with matching content if user can not see the issue" do
-        user = create(:user)
-        expect(described_class.search(confidential_note.note, as_user: user)).to be_empty
-      end
-
-      it "does not return notes with matching content for project members with guest role" do
-        user = create(:user)
-        project.team << [user, :guest]
-        expect(described_class.search(confidential_note.note, as_user: user)).to be_empty
-      end
-
-      it "does not return notes with matching content for unauthenticated users" do
-        expect(described_class.search(confidential_note.note)).to be_empty
-      end
-    end
-  end
-
   describe "editable?" do
     it "returns true" do
       note = build(:note)