Merge branch '52123-issuable-actions-notesfinder-pderichs' into 'master'

Use NotesFinder to fetch notes on API and Controllers

Closes #52123

See merge request gitlab-org/gitlab-ce!31300

15 files changed, 316 insertions, 78 deletions

diff --git a/app/controllers/concerns/issuable_actions.rb b/app/controllers/concerns/issuable_actions.rb
index 6fa2f75be33..398cb728e05 100644
--- a/app/controllers/concerns/issuable_actions.rb
+++ b/app/controllers/concerns/issuable_actions.rb
@@ -98,13 +98,12 @@ module IssuableActions
     render json: { notice: "#{quantity} #{resource_name.pluralize(quantity)} updated" }
   end
 
-  # rubocop: disable CodeReuse/ActiveRecord
+  # rubocop:disable CodeReuse/ActiveRecord
   def discussions
-    notes = issuable.discussion_notes
-      .inc_relations_for_view
-      .with_notes_filter(notes_filter)
-      .includes(:noteable)
-      .fresh
+    notes = NotesFinder.new(current_user, finder_params_for_issuable).execute
+                .inc_relations_for_view
+                .includes(:noteable)
+                .fresh
 
     if notes_filter != UserPreference::NOTES_FILTERS[:only_comments]
       notes = ResourceEvents::MergeIntoNotesService.new(issuable, current_user).execute(notes)
@@ -117,7 +116,7 @@ module IssuableActions
 
     render json: discussion_serializer.represent(discussions, context: self)
   end
-  # rubocop: enable CodeReuse/ActiveRecord
+  # rubocop:enable CodeReuse/ActiveRecord
 
   private
 
@@ -222,4 +221,13 @@ module IssuableActions
   def parent
     @project || @group # rubocop:disable Gitlab/ModuleWithInstanceVariables
   end
+
+  # rubocop:disable Gitlab/ModuleWithInstanceVariables
+  def finder_params_for_issuable
+    {
+        target: @issuable,
+        notes_filter: notes_filter
+    }.tap { |new_params| new_params[:project] = project if respond_to?(:project, true) }
+  end
+  # rubocop:enable Gitlab/ModuleWithInstanceVariables
 end
diff --git a/app/controllers/concerns/notes_actions.rb b/app/controllers/concerns/notes_actions.rb
index 0098c4cdf4c..d2a961efff7 100644
--- a/app/controllers/concerns/notes_actions.rb
+++ b/app/controllers/concerns/notes_actions.rb
@@ -243,7 +243,7 @@ module NotesActions
   end
 
   def notes_finder
-    @notes_finder ||= NotesFinder.new(project, current_user, finder_params)
+    @notes_finder ||= NotesFinder.new(current_user, finder_params)
   end
 
   def note_serializer
diff --git a/app/controllers/projects/notes_controller.rb b/app/controllers/projects/notes_controller.rb
index 3152a38fd8e..65d9b074eee 100644
--- a/app/controllers/projects/notes_controller.rb
+++ b/app/controllers/projects/notes_controller.rb
@@ -68,7 +68,7 @@ class Projects::NotesController < Projects::ApplicationController
   alias_method :awardable, :note
 
   def finder_params
-    params.merge(last_fetched_at: last_fetched_at, notes_filter: notes_filter)
+    params.merge(project: project, last_fetched_at: last_fetched_at, notes_filter: notes_filter)
   end
 
   def authorize_admin_note!
diff --git a/app/controllers/snippets/notes_controller.rb b/app/controllers/snippets/notes_controller.rb
index 612897f27e6..551b37cb3d3 100644
--- a/app/controllers/snippets/notes_controller.rb
+++ b/app/controllers/snippets/notes_controller.rb
@@ -27,7 +27,9 @@ class Snippets::NotesController < ApplicationController
   alias_method :noteable, :snippet
 
   def finder_params
-    params.merge(last_fetched_at: last_fetched_at, target_id: snippet.id, target_type: 'personal_snippet')
+    params.merge(last_fetched_at: last_fetched_at, target_id: snippet.id, target_type: 'personal_snippet').tap do |merged_params|
+      merged_params[:project] = project if respond_to?(:project)
+    end
   end
 
   def authorize_read_snippet!
diff --git a/app/finders/notes_finder.rb b/app/finders/notes_finder.rb
index 8f610d7dddb..f7d9100bb78 100644
--- a/app/finders/notes_finder.rb
+++ b/app/finders/notes_finder.rb
@@ -3,6 +3,8 @@
 class NotesFinder
   FETCH_OVERLAP = 5.seconds
 
+  attr_reader :target_type
+
   # Used to filter Notes
   # When used with target_type and target_id this returns notes specifically for the controller
   #
@@ -10,15 +12,17 @@ class NotesFinder
   #   current_user - which user check authorizations with
   #   project - which project to look for notes on
   #   params:
+  #     target: noteable
   #     target_type: string
   #     target_id: integer
   #     last_fetched_at: time
   #     search: string
   #
-  def initialize(project, current_user, params = {})
-    @project = project
+  def initialize(current_user, params = {})
+    @project = params[:project]
     @current_user = current_user
-    @params = params
+    @params = params.dup
+    @target_type = @params[:target_type]
   end
 
   def execute
@@ -32,7 +36,27 @@ class NotesFinder
   def target
     return @target if defined?(@target)
 
-    target_type = @params[:target_type]
+    if target_given?
+      use_explicit_target
+    else
+      find_target_by_type_and_ids
+    end
+  end
+
+  private
+
+  def target_given?
+    @params.key?(:target)
+  end
+
+  def use_explicit_target
+    @target = @params[:target]
+    @target_type = @target.class.name.underscore
+
+    @target
+  end
+
+  def find_target_by_type_and_ids
     target_id   = @params[:target_id]
     target_iid  = @params[:target_iid]
 
@@ -45,13 +69,11 @@ class NotesFinder
           @project.commit(target_id)
         end
       else
-        noteables_for_type_by_id(target_type, target_id, target_iid)
+        noteable_for_type_by_id(target_type, target_id, target_iid)
       end
   end
 
-  private
-
-  def noteables_for_type_by_id(type, id, iid)
+  def noteable_for_type_by_id(type, id, iid)
     query = if id
               { id: id }
             else
@@ -77,10 +99,6 @@ class NotesFinder
     search(notes)
   end
 
-  def target_type
-    @params[:target_type]
-  end
-
   # rubocop: disable CodeReuse/ActiveRecord
   def notes_of_any_type
     types = %w(commit issue merge_request snippet)
diff --git a/lib/api/helpers/notes_helpers.rb b/lib/api/helpers/notes_helpers.rb
index b03ac7deb71..7124ac0c5c3 100644
--- a/lib/api/helpers/notes_helpers.rb
+++ b/lib/api/helpers/notes_helpers.rb
@@ -76,7 +76,7 @@ module API
       def find_noteable(parent_type, parent_id, noteable_type, noteable_id)
         params = params_by_noteable_type_and_id(noteable_type, noteable_id)
 
-        noteable = NotesFinder.new(user_project, current_user, params).target
+        noteable = NotesFinder.new(current_user, params.merge(project: user_project)).target
         noteable = nil unless can?(current_user, noteable_read_ability_name(noteable), noteable)
         noteable || not_found!(noteable_type)
       end
diff --git a/lib/gitlab/project_search_results.rb b/lib/gitlab/project_search_results.rb
index 0f3b97e2317..827f4f77f36 100644
--- a/lib/gitlab/project_search_results.rb
+++ b/lib/gitlab/project_search_results.rb
@@ -108,7 +108,7 @@ module Gitlab
 
     # rubocop: disable CodeReuse/ActiveRecord
     def notes_finder(type)
-      NotesFinder.new(project, @current_user, search: query, target_type: type).execute.user.order('updated_at DESC')
+      NotesFinder.new(@current_user, search: query, target_type: type, project: project).execute.user.order('updated_at DESC')
     end
     # rubocop: enable CodeReuse/ActiveRecord
 
diff --git a/spec/controllers/concerns/issuable_actions_spec.rb b/spec/controllers/concerns/issuable_actions_spec.rb
new file mode 100644
index 00000000000..7b0b4497f3f
--- /dev/null
+++ b/spec/controllers/concerns/issuable_actions_spec.rb
@@ -0,0 +1,69 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe IssuableActions do
+  let(:project) { double('project') }
+  let(:user) { double('user') }
+  let(:issuable) { double('issuable') }
+  let(:finder_params_for_issuable) { {} }
+  let(:notes_result) { double('notes_result') }
+  let(:discussion_serializer) { double('discussion_serializer') }
+
+  let(:controller) do
+    klass = Class.new do
+      attr_reader :current_user, :project, :issuable
+
+      def self.before_action(action, params = nil)
+      end
+
+      include IssuableActions
+
+      def initialize(issuable, project, user, finder_params)
+        @issuable = issuable
+        @project = project
+        @current_user = user
+        @finder_params = finder_params
+      end
+
+      def finder_params_for_issuable
+        @finder_params
+      end
+
+      def params
+        {
+          notes_filter: 1
+        }
+      end
+
+      def prepare_notes_for_rendering(notes)
+        []
+      end
+
+      def render(options)
+      end
+    end
+
+    klass.new(issuable, project, user, finder_params_for_issuable)
+  end
+
+  describe '#discussions' do
+    before do
+      allow(user).to receive(:set_notes_filter)
+      allow(user).to receive(:user_preference)
+      allow(discussion_serializer).to receive(:represent)
+    end
+
+    it 'instantiates and calls NotesFinder as expected' do
+      expect(Discussion).to receive(:build_collection).and_return([])
+      expect(DiscussionSerializer).to receive(:new).and_return(discussion_serializer)
+      expect(NotesFinder).to receive(:new).with(user, finder_params_for_issuable).and_call_original
+
+      expect_any_instance_of(NotesFinder).to receive(:execute).and_return(notes_result)
+
+      expect(notes_result).to receive_messages(inc_relations_for_view: notes_result, includes: notes_result, fresh: notes_result)
+
+      controller.discussions
+    end
+  end
+end
diff --git a/spec/controllers/projects/issues_controller_spec.rb b/spec/controllers/projects/issues_controller_spec.rb
index 32d14dce936..0f885d776e1 100644
--- a/spec/controllers/projects/issues_controller_spec.rb
+++ b/spec/controllers/projects/issues_controller_spec.rb
@@ -1260,6 +1260,28 @@ describe Projects::IssuesController do
         sign_in(user)
       end
 
+      context do
+        it_behaves_like 'discussions provider' do
+          let!(:author) { create(:user) }
+          let!(:project) { create(:project) }
+
+          let!(:issue) { create(:issue, project: project, author: user) }
+
+          let!(:note_on_issue1) { create(:discussion_note_on_issue, noteable: issue, project: issue.project, author: create(:user)) }
+          let!(:note_on_issue2) { create(:discussion_note_on_issue, noteable: issue, project: issue.project, author: create(:user)) }
+
+          let(:requested_iid) { issue.iid }
+          let(:expected_discussion_count) { 3 }
+          let(:expected_discussion_ids) do
+            [
+              issue.notes.first.discussion_id,
+              note_on_issue1.discussion_id,
+              note_on_issue2.discussion_id
+            ]
+          end
+        end
+      end
+
       it 'returns discussion json' do
         get :discussions, params: { namespace_id: project.namespace, project_id: project, id: issue.iid }
 
diff --git a/spec/controllers/projects/merge_requests_controller_spec.rb b/spec/controllers/projects/merge_requests_controller_spec.rb
index 57a432de3f5..b1dc6a65dd4 100644
--- a/spec/controllers/projects/merge_requests_controller_spec.rb
+++ b/spec/controllers/projects/merge_requests_controller_spec.rb
@@ -1210,6 +1210,22 @@ describe Projects::MergeRequestsController do
         end
       end
     end
+
+    context do
+      it_behaves_like 'discussions provider' do
+        let!(:author) { create(:user) }
+        let!(:project) { create(:project) }
+
+        let!(:merge_request) { create(:merge_request, source_project: project) }
+
+        let!(:mr_note1) { create(:discussion_note_on_merge_request, noteable: merge_request, project: project) }
+        let!(:mr_note2) { create(:discussion_note_on_merge_request, noteable: merge_request, project: project) }
+
+        let(:requested_iid) { merge_request.iid }
+        let(:expected_discussion_count) { 2 }
+        let(:expected_discussion_ids) { [mr_note1.discussion_id, mr_note2.discussion_id] }
+      end
+    end
   end
 
   describe 'GET edit' do
diff --git a/spec/controllers/projects/notes_controller_spec.rb b/spec/controllers/projects/notes_controller_spec.rb
index 98aea9056dc..9ab565dc2e8 100644
--- a/spec/controllers/projects/notes_controller_spec.rb
+++ b/spec/controllers/projects/notes_controller_spec.rb
@@ -43,7 +43,7 @@ describe Projects::NotesController do
       request.headers['X-Last-Fetched-At'] = last_fetched_at
 
       expect(NotesFinder).to receive(:new)
-        .with(anything, anything, hash_including(last_fetched_at: last_fetched_at))
+        .with(anything, hash_including(last_fetched_at: last_fetched_at))
         .and_call_original
 
       get :index, params: request_params
diff --git a/spec/finders/notes_finder_spec.rb b/spec/finders/notes_finder_spec.rb
index 87bde4ca2f6..88906adfeeb 100644
--- a/spec/finders/notes_finder_spec.rb
+++ b/spec/finders/notes_finder_spec.rb
@@ -14,7 +14,7 @@ describe NotesFinder do
       let!(:system_note) { create(:note_on_issue, project: project, system: true) }
 
       it 'returns only user notes when using only_comments filter' do
-        finder = described_class.new(project, user, notes_filter: UserPreference::NOTES_FILTERS[:only_comments])
+        finder = described_class.new(user, project: project, notes_filter: UserPreference::NOTES_FILTERS[:only_comments])
 
         notes = finder.execute
 
@@ -22,7 +22,7 @@ describe NotesFinder do
       end
 
       it 'returns only system notes when using only_activity filters' do
-        finder = described_class.new(project, user, notes_filter: UserPreference::NOTES_FILTERS[:only_activity])
+        finder = described_class.new(user, project: project, notes_filter: UserPreference::NOTES_FILTERS[:only_activity])
 
         notes = finder.execute
 
@@ -30,7 +30,7 @@ describe NotesFinder do
       end
 
       it 'gets all notes' do
-        finder = described_class.new(project, user, notes_filter: UserPreference::NOTES_FILTERS[:all_activity])
+        finder = described_class.new(user, project: project, notes_filter: UserPreference::NOTES_FILTERS[:all_activity])
 
         notes = finder.execute
 
@@ -41,7 +41,7 @@ describe NotesFinder do
     it 'finds notes on merge requests' do
       create(:note_on_merge_request, project: project)
 
-      notes = described_class.new(project, user).execute
+      notes = described_class.new(user, project: project).execute
 
       expect(notes.count).to eq(1)
     end
@@ -49,7 +49,7 @@ describe NotesFinder do
     it 'finds notes on snippets' do
       create(:note_on_project_snippet, project: project)
 
-      notes = described_class.new(project, user).execute
+      notes = described_class.new(user, project: project).execute
 
       expect(notes.count).to eq(1)
     end
@@ -59,13 +59,13 @@ describe NotesFinder do
       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
+      notes = described_class.new(create(:user), params).execute
 
       expect(notes.count).to eq(0)
     end
 
     it 'succeeds when no notes found' do
-      notes = described_class.new(project, create(:user)).execute
+      notes = described_class.new(create(:user), project: project).execute
 
       expect(notes.count).to eq(0)
     end
@@ -82,7 +82,7 @@ describe NotesFinder do
       it 'publicly excludes notes on merge requests' do
         create(:note_on_merge_request, project: project)
 
-        notes = described_class.new(project, create(:user)).execute
+        notes = described_class.new(create(:user), project: project).execute
 
         expect(notes.count).to eq(0)
       end
@@ -90,7 +90,7 @@ describe NotesFinder do
       it 'publicly excludes notes on issues' do
         create(:note_on_issue, project: project)
 
-        notes = described_class.new(project, create(:user)).execute
+        notes = described_class.new(create(:user), project: project).execute
 
         expect(notes.count).to eq(0)
       end
@@ -98,7 +98,7 @@ describe NotesFinder do
       it 'publicly excludes notes on snippets' do
         create(:note_on_project_snippet, project: project)
 
-        notes = described_class.new(project, create(:user)).execute
+        notes = described_class.new(create(:user), project: project).execute
 
         expect(notes.count).to eq(0)
       end
@@ -110,7 +110,7 @@ describe NotesFinder do
       let!(:note2) { create :note_on_commit, project: project }
 
       it 'finds only notes for the selected type' do
-        notes = described_class.new(project, user, target_type: 'issue').execute
+        notes = described_class.new(user, project: project, target_type: 'issue').execute
 
         expect(notes).to eq([note1])
       end
@@ -118,56 +118,51 @@ describe NotesFinder do
 
     context 'for target' do
       let(:project) { create(:project, :repository) }
-      let(:note1) { create :note_on_commit, project: project }
-      let(:note2) { create :note_on_commit, project: 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
+      let(:params) { { project: project, target_id: commit.id, target_type: 'commit', last_fetched_at: 1.hour.ago.to_i } }
 
       it 'finds all notes' do
-        notes = described_class.new(project, user, params).execute
+        notes = described_class.new(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 }
+        params = { project: project, target_type: 'merge_request', target_id: note.noteable.id }
 
-        notes = described_class.new(project, user, params).execute
+        notes = described_class.new(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 }
+        params = { project: project, target_type: 'snippet', target_id: note.noteable.id }
 
-        notes = described_class.new(project, user, params).execute
+        notes = described_class.new(user, params).execute
 
         expect(notes.count).to eq(1)
       end
 
       it 'finds notes on personal snippets' do
         note = create(:note_on_personal_snippet)
-        params = { target_type: 'personal_snippet', target_id: note.noteable_id }
+        params = { project: project, target_type: 'personal_snippet', target_id: note.noteable_id }
 
-        notes = described_class.new(project, user, params).execute
+        notes = described_class.new(user, params).execute
 
         expect(notes.count).to eq(1)
       end
 
       it 'raises an exception for an invalid target_type' do
         params[:target_type] = 'invalid'
-        expect { described_class.new(project, user, params).execute }.to raise_error("invalid target_type '#{params[:target_type]}'")
+        expect { described_class.new(user, params).execute }.to raise_error("invalid target_type '#{params[: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
+        notes = described_class.new(user, params).execute
         expect(notes).to eq([note1])
       end
 
@@ -175,25 +170,47 @@ describe NotesFinder 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 } }
+        let(:params) { { project: confidential_issue.project, 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])
+          expect(described_class.new(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)
+          expect { described_class.new(user, params).execute }.to raise_error(ActiveRecord::RecordNotFound)
         end
 
         it 'raises an error for project members with guest role' do
           user = create(:user)
           project.add_guest(user)
 
-          expect { described_class.new(project, user, params).execute }.to raise_error(ActiveRecord::RecordNotFound)
+          expect { described_class.new(user, params).execute }.to raise_error(ActiveRecord::RecordNotFound)
         end
       end
     end
+
+    context 'for explicit target' do
+      let(:project) { create(:project, :repository) }
+      let!(:note1) { create :note_on_commit, project: project, created_at: 1.day.ago, updated_at: 2.hours.ago }
+      let!(:note2) { create :note_on_commit, project: project }
+      let(:commit) { note1.noteable }
+      let(:params) { { project: project, target: commit } }
+
+      it 'returns the expected notes' do
+        expect(described_class.new(user, params).execute).to eq([note1, note2])
+      end
+
+      it 'returns the expected notes when last_fetched_at is given' do
+        params = { project: project, target: commit, last_fetched_at: 1.hour.ago.to_i }
+        expect(described_class.new(user, params).execute).to eq([note2])
+      end
+
+      it 'fails when nil is provided' do
+        params = { project: project, target: nil }
+        expect { described_class.new(user, params).execute }.to raise_error(RuntimeError)
+      end
+    end
   end
 
   describe '.search' do
@@ -201,17 +218,17 @@ describe NotesFinder do
     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])
+      expect(described_class.new(nil, project: note.project, 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])
+      expect(described_class.new(nil, project: note.project, 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])
+      expect(described_class.new(create(:user), project: note.project, search: note.note).execute).to eq([note])
     end
 
     context "confidential issues" do
@@ -220,27 +237,27 @@ describe NotesFinder do
       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])
+        expect(described_class.new(user, project: confidential_note.project, 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(described_class.new(confidential_note.project, user, search: confidential_note.note).execute).to be_empty
+        expect(described_class.new(user, project: confidential_note.project, search: confidential_note.note).execute).to be_empty
       end
 
       it "does not return notes with matching content for project members with guest role" do
         user = create(:user)
         project.add_guest(user)
-        expect(described_class.new(confidential_note.project, user, search: confidential_note.note).execute).to be_empty
+        expect(described_class.new(user, project: confidential_note.project, 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
+        expect(described_class.new(nil, project: confidential_note.project, 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(:sql) { described_class.new(nil, project: note.project, search: note.note).execute.to_sql }
       let(:number_of_noteable_types) { 4 }
 
       specify 'project_id check' do
@@ -254,11 +271,11 @@ describe NotesFinder do
   end
 
   describe '#target' do
-    subject { described_class.new(project, user, params) }
+    subject { described_class.new(user, params) }
 
     context 'for a issue target' do
       let(:issue) { create(:issue, project: project) }
-      let(:params) { { target_type: 'issue', target_id: issue.id } }
+      let(:params) { { project: project, target_type: 'issue', target_id: issue.id } }
 
       it 'returns the issue' do
         expect(subject.target).to eq(issue)
@@ -267,7 +284,7 @@ describe NotesFinder do
 
     context 'for a merge request target' do
       let(:merge_request) { create(:merge_request, source_project: project) }
-      let(:params) { { target_type: 'merge_request', target_id: merge_request.id } }
+      let(:params) { { project: project, target_type: 'merge_request', target_id: merge_request.id } }
 
       it 'returns the merge_request' do
         expect(subject.target).to eq(merge_request)
@@ -276,7 +293,7 @@ describe NotesFinder do
 
     context 'for a snippet target' do
       let(:snippet) { create(:project_snippet, project: project) }
-      let(:params) { { target_type: 'snippet', target_id: snippet.id } }
+      let(:params) { { project: project, target_type: 'snippet', target_id: snippet.id } }
 
       it 'returns the snippet' do
         expect(subject.target).to eq(snippet)
@@ -286,7 +303,7 @@ describe NotesFinder do
     context 'for a commit target' do
       let(:project) { create(:project, :repository) }
       let(:commit) { project.commit }
-      let(:params) { { target_type: 'commit', target_id: commit.id } }
+      let(:params) { { project: project, target_type: 'commit', target_id: commit.id } }
 
       it 'returns the commit' do
         expect(subject.target).to eq(commit)
@@ -298,24 +315,24 @@ describe NotesFinder do
       let(:merge_request) { create(:merge_request, source_project: project, target_project: project) }
 
       it 'finds issues by iid' do
-        iid_params = { target_type: 'issue', target_iid: issue.iid }
-        expect(described_class.new(project, user, iid_params).target).to eq(issue)
+        iid_params = { project: project, target_type: 'issue', target_iid: issue.iid }
+        expect(described_class.new(user, iid_params).target).to eq(issue)
       end
 
       it 'finds merge requests by iid' do
-        iid_params = { target_type: 'merge_request', target_iid: merge_request.iid }
-        expect(described_class.new(project, user, iid_params).target).to eq(merge_request)
+        iid_params = { project: project, target_type: 'merge_request', target_iid: merge_request.iid }
+        expect(described_class.new(user, iid_params).target).to eq(merge_request)
       end
 
       it 'returns nil if both target_id and target_iid are not given' do
-        params_without_any_id = { target_type: 'issue' }
-        expect(described_class.new(project, user, params_without_any_id).target).to be_nil
+        params_without_any_id = { project: project, target_type: 'issue' }
+        expect(described_class.new(user, params_without_any_id).target).to be_nil
       end
 
       it 'prioritizes target_id over target_iid' do
         issue2 = create(:issue, project: project)
-        iid_params = { target_type: 'issue', target_id: issue2.id, target_iid: issue.iid }
-        expect(described_class.new(project, user, iid_params).target).to eq(issue2)
+        iid_params = { project: project, target_type: 'issue', target_id: issue2.id, target_iid: issue.iid }
+        expect(described_class.new(user, iid_params).target).to eq(issue2)
       end
     end
   end
diff --git a/spec/fixtures/api/schemas/entities/discussion.json b/spec/fixtures/api/schemas/entities/discussion.json
new file mode 100644
index 00000000000..bcc1db79e83
--- /dev/null
+++ b/spec/fixtures/api/schemas/entities/discussion.json
@@ -0,0 +1,67 @@
+{
+  "type": "object",
+  "required" : [
+    "id",
+    "notes",
+    "individual_note"
+  ],
+  "properties" : {
+    "id": { "type": "string" },
+    "individual_note": { "type": "boolean" },
+    "notes": {
+      "type": "array",
+      "items": {
+        "type": "object",
+        "properties" : {
+          "id": { "type": "string" },
+          "type": { "type": ["string", "null"] },
+          "body": { "type": "string" },
+          "attachment": { "type": ["string", "null"]},
+          "award_emoji": { "type": "array" },
+          "author": {
+            "type": "object",
+            "properties": {
+              "name": { "type": "string" },
+              "username": { "type": "string" },
+              "id": { "type": "integer" },
+              "state": { "type": "string" },
+              "avatar_url": { "type": "uri" },
+              "web_url": { "type": "uri" },
+              "status_tooltip_html": { "type": ["string", "null"] },
+              "path": { "type": "string" }
+            },
+            "additionalProperties": false
+          },
+          "created_at": { "type": "date" },
+          "updated_at": { "type": "date" },
+          "system": { "type": "boolean" },
+          "noteable_id": { "type": "integer" },
+          "noteable_iid": { "type": "integer" },
+          "noteable_type": { "type": "string" },
+          "resolved": { "type": "boolean" },
+          "resolvable": { "type": "boolean" },
+          "resolved_by": { "type": ["string", "null"] },
+          "note": { "type": "string" },
+          "note_html": { "type": "string"  },
+          "current_user": { "type": "object" },
+          "suggestions": { "type": "array" },
+          "discussion_id": { "type": "string" },
+          "emoji_awardable": { "type": "boolean" },
+          "report_abuse_path": { "type": "string" },
+          "noteable_note_url": { "type": "string" },
+          "resolve_path": { "type": "string" },
+          "resolve_with_issue_path": { "type": "string" },
+          "cached_markdown_version": { "type": "integer" },
+          "human_access": { "type": ["string", "null"] },
+          "toggle_award_path": { "type": "string" },
+          "path": { "type": "string" }
+        },
+        "required": [
+          "id", "attachment", "author", "created_at", "updated_at",
+          "system", "noteable_id", "noteable_type"
+        ],
+        "additionalProperties": false
+      }
+    }
+  }
+}
diff --git a/spec/fixtures/api/schemas/entities/discussions.json b/spec/fixtures/api/schemas/entities/discussions.json
new file mode 100644
index 00000000000..5a837429776
--- /dev/null
+++ b/spec/fixtures/api/schemas/entities/discussions.json
@@ -0,0 +1,4 @@
+{
+  "type": "array",
+  "items": { "$ref": "discussion.json" }
+}
diff --git a/spec/support/shared_examples/discussions_provider_shared_examples.rb b/spec/support/shared_examples/discussions_provider_shared_examples.rb
new file mode 100644
index 00000000000..77cf1ac3f51
--- /dev/null
+++ b/spec/support/shared_examples/discussions_provider_shared_examples.rb
@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+shared_examples 'discussions provider' do
+  it 'returns the expected discussions' do
+    get :discussions, params: { namespace_id: project.namespace, project_id: project, id: requested_iid }
+
+    expect(response).to have_gitlab_http_status(200)
+    expect(response).to match_response_schema('entities/discussions')
+
+    expect(json_response.size).to eq(expected_discussion_count)
+    expect(json_response.pluck('id')).to eq(expected_discussion_ids)
+  end
+end