GraphQL mutations for managing Notes

https://gitlab.com/gitlab-org/gitlab-ce/issues/62826

21 files changed, 683 insertions, 1 deletions

diff --git a/app/graphql/mutations/notes/base.rb b/app/graphql/mutations/notes/base.rb
new file mode 100644
index 00000000000..a7198f5fba6
--- /dev/null
+++ b/app/graphql/mutations/notes/base.rb
@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+module Mutations
+  module Notes
+    class Base < BaseMutation
+      include Gitlab::Graphql::Authorize::AuthorizeResource
+
+      field :note,
+            Types::Notes::NoteType,
+            null: true,
+            description: 'The note after mutation'
+
+      private
+
+      def find_object(id:)
+        GitlabSchema.object_from_id(id)
+      end
+
+      def check_object_is_noteable!(object)
+        unless object.is_a?(Noteable)
+          raise Gitlab::Graphql::Errors::ResourceNotAvailable,
+                'Cannot add notes to this resource'
+        end
+      end
+
+      def check_object_is_note!(object)
+        unless object.is_a?(Note)
+          raise Gitlab::Graphql::Errors::ResourceNotAvailable,
+                'Resource is not a note'
+        end
+      end
+    end
+  end
+end
diff --git a/app/graphql/mutations/notes/create/base.rb b/app/graphql/mutations/notes/create/base.rb
new file mode 100644
index 00000000000..d3a5dae2188
--- /dev/null
+++ b/app/graphql/mutations/notes/create/base.rb
@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+
+module Mutations
+  module Notes
+    module Create
+      # This is a Base class for the Note creation Mutations and is not
+      # mounted as a GraphQL mutation itself.
+      class Base < Mutations::Notes::Base
+        authorize :create_note
+
+        argument :noteable_id,
+                  GraphQL::ID_TYPE,
+                  required: true,
+                  description: 'The global id of the resource to add a note to'
+
+        argument :body,
+                  GraphQL::STRING_TYPE,
+                  required: true,
+                  description: copy_field_description(Types::Notes::NoteType, :body)
+
+        private
+
+        def resolve(args)
+          noteable = authorized_find!(id: args[:noteable_id])
+
+          check_object_is_noteable!(noteable)
+
+          note = ::Notes::CreateService.new(
+            noteable.project,
+            current_user,
+            create_note_params(noteable, args)
+          ).execute
+
+          {
+            note: (note if note.persisted?),
+            errors: errors_on_object(note)
+          }
+        end
+
+        def create_note_params(noteable, args)
+          {
+            noteable: noteable,
+            note: args[:body]
+          }
+        end
+      end
+    end
+  end
+end
diff --git a/app/graphql/mutations/notes/create/diff_note.rb b/app/graphql/mutations/notes/create/diff_note.rb
new file mode 100644
index 00000000000..9b5f3092006
--- /dev/null
+++ b/app/graphql/mutations/notes/create/diff_note.rb
@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+module Mutations
+  module Notes
+    module Create
+      class DiffNote < Base
+        graphql_name 'CreateDiffNote'
+
+        argument :position,
+                  Types::Notes::DiffPositionInputType,
+                  required: true,
+                  description: copy_field_description(Types::Notes::NoteType, :position)
+
+        private
+
+        def create_note_params(noteable, args)
+          super(noteable, args).merge({
+            type: 'DiffNote',
+            position: position(noteable, args)
+          })
+        end
+
+        def position(noteable, args)
+          position = args[:position].to_h
+          position[:position_type] = 'text'
+          position.merge!(position[:paths].to_h)
+
+          Gitlab::Diff::Position.new(position)
+        end
+      end
+    end
+  end
+end
diff --git a/app/graphql/mutations/notes/create/image_diff_note.rb b/app/graphql/mutations/notes/create/image_diff_note.rb
new file mode 100644
index 00000000000..d94fd4d6ff8
--- /dev/null
+++ b/app/graphql/mutations/notes/create/image_diff_note.rb
@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+module Mutations
+  module Notes
+    module Create
+      class ImageDiffNote < Base
+        graphql_name 'CreateImageDiffNote'
+
+        argument :position,
+                  Types::Notes::DiffImagePositionInputType,
+                  required: true,
+                  description: copy_field_description(Types::Notes::NoteType, :position)
+
+        private
+
+        def create_note_params(noteable, args)
+          super(noteable, args).merge({
+            type: 'DiffNote',
+            position: position(noteable, args)
+          })
+        end
+
+        def position(noteable, args)
+          position = args[:position].to_h
+          position[:position_type] = 'image'
+          position.merge!(position[:paths].to_h)
+
+          Gitlab::Diff::Position.new(position)
+        end
+      end
+    end
+  end
+end
diff --git a/app/graphql/mutations/notes/create/note.rb b/app/graphql/mutations/notes/create/note.rb
new file mode 100644
index 00000000000..3c571a4538f
--- /dev/null
+++ b/app/graphql/mutations/notes/create/note.rb
@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+module Mutations
+  module Notes
+    module Create
+      class Note < Base
+        graphql_name 'CreateNote'
+      end
+    end
+  end
+end
diff --git a/app/graphql/mutations/notes/destroy.rb b/app/graphql/mutations/notes/destroy.rb
new file mode 100644
index 00000000000..a81322bc9b7
--- /dev/null
+++ b/app/graphql/mutations/notes/destroy.rb
@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+module Mutations
+  module Notes
+    class Destroy < Base
+      graphql_name 'DestroyNote'
+
+      authorize :admin_note
+
+      argument :id,
+                GraphQL::ID_TYPE,
+                required: true,
+                description: 'The global id of the note to destroy'
+
+      def resolve(id:)
+        note = authorized_find!(id: id)
+
+        check_object_is_note!(note)
+
+        ::Notes::DestroyService.new(note.project, current_user).execute(note)
+
+        {
+          errors: []
+        }
+      end
+    end
+  end
+end
diff --git a/app/graphql/mutations/notes/update.rb b/app/graphql/mutations/notes/update.rb
new file mode 100644
index 00000000000..ebf57b800c0
--- /dev/null
+++ b/app/graphql/mutations/notes/update.rb
@@ -0,0 +1,38 @@
+# frozen_string_literal: true
+
+module Mutations
+  module Notes
+    class Update < Base
+      graphql_name 'UpdateNote'
+
+      authorize :admin_note
+
+      argument :id,
+                GraphQL::ID_TYPE,
+                required: true,
+                description: 'The global id of the note to update'
+
+      argument :body,
+                GraphQL::STRING_TYPE,
+                required: true,
+                description: copy_field_description(Types::Notes::NoteType, :body)
+
+      def resolve(args)
+        note = authorized_find!(id: args[:id])
+
+        check_object_is_note!(note)
+
+        note = ::Notes::UpdateService.new(
+          note.project,
+          current_user,
+          { note: args[:body] }
+        ).execute(note)
+
+        {
+          note: note.reset,
+          errors: errors_on_object(note)
+        }
+      end
+    end
+  end
+end
diff --git a/app/graphql/types/base_input_object.rb b/app/graphql/types/base_input_object.rb
index aebed035d3b..90a29b0cfb8 100644
--- a/app/graphql/types/base_input_object.rb
+++ b/app/graphql/types/base_input_object.rb
@@ -2,5 +2,6 @@
 
 module Types
   class BaseInputObject < GraphQL::Schema::InputObject
+    prepend Gitlab::Graphql::CopyFieldDescription
   end
 end
diff --git a/app/graphql/types/diff_paths_input_type.rb b/app/graphql/types/diff_paths_input_type.rb
new file mode 100644
index 00000000000..43feddd9827
--- /dev/null
+++ b/app/graphql/types/diff_paths_input_type.rb
@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+module Types
+  # rubocop: disable Graphql/AuthorizeTypes
+  class DiffPathsInputType < BaseInputObject
+    argument :old_path, GraphQL::STRING_TYPE, required: false,
+              description: 'The path of the file on the start sha'
+    argument :new_path, GraphQL::STRING_TYPE, required: false,
+              description: 'The path of the file on the head sha'
+  end
+  # rubocop: enable Graphql/AuthorizeTypes
+end
diff --git a/app/graphql/types/mutation_type.rb b/app/graphql/types/mutation_type.rb
index bc5fb709522..f843d6ad86f 100644
--- a/app/graphql/types/mutation_type.rb
+++ b/app/graphql/types/mutation_type.rb
@@ -10,5 +10,10 @@ module Types
     mount_mutation Mutations::AwardEmojis::Remove
     mount_mutation Mutations::AwardEmojis::Toggle
     mount_mutation Mutations::MergeRequests::SetWip, calls_gitaly: true
+    mount_mutation Mutations::Notes::Create::Note, calls_gitaly: true
+    mount_mutation Mutations::Notes::Create::DiffNote, calls_gitaly: true
+    mount_mutation Mutations::Notes::Create::ImageDiffNote, calls_gitaly: true
+    mount_mutation Mutations::Notes::Update
+    mount_mutation Mutations::Notes::Destroy
   end
 end
diff --git a/app/graphql/types/notes/diff_image_position_input_type.rb b/app/graphql/types/notes/diff_image_position_input_type.rb
new file mode 100644
index 00000000000..23b53b20815
--- /dev/null
+++ b/app/graphql/types/notes/diff_image_position_input_type.rb
@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+module Types
+  module Notes
+    # rubocop: disable Graphql/AuthorizeTypes
+    class DiffImagePositionInputType < DiffPositionBaseInputType
+      graphql_name 'DiffImagePositionInput'
+
+      argument :x, GraphQL::INT_TYPE, required: true,
+               description: copy_field_description(Types::Notes::DiffPositionType, :x)
+      argument :y, GraphQL::INT_TYPE, required: true,
+               description: copy_field_description(Types::Notes::DiffPositionType, :y)
+      argument :width, GraphQL::INT_TYPE, required: true,
+               description: copy_field_description(Types::Notes::DiffPositionType, :width)
+      argument :height, GraphQL::INT_TYPE, required: true,
+               description: copy_field_description(Types::Notes::DiffPositionType, :height)
+    end
+    # rubocop: enable Graphql/AuthorizeTypes
+  end
+end
diff --git a/app/graphql/types/notes/diff_position_base_input_type.rb b/app/graphql/types/notes/diff_position_base_input_type.rb
new file mode 100644
index 00000000000..a8991a1240a
--- /dev/null
+++ b/app/graphql/types/notes/diff_position_base_input_type.rb
@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+module Types
+  module Notes
+    # rubocop: disable Graphql/AuthorizeTypes
+    class DiffPositionBaseInputType < BaseInputObject
+      argument :head_sha, GraphQL::STRING_TYPE, required: true,
+               description: copy_field_description(Types::Notes::DiffPositionType, :head_sha)
+      argument :base_sha,  GraphQL::STRING_TYPE, required: false,
+               description: copy_field_description(Types::Notes::DiffPositionType, :base_sha)
+      argument :start_sha, GraphQL::STRING_TYPE, required: true,
+               description: copy_field_description(Types::Notes::DiffPositionType, :start_sha)
+
+      argument :paths,
+               Types::DiffPathsInputType,
+               required: true,
+               description: 'The paths of the file that was changed. ' \
+                            'Both of the properties of this input are optional, but at least one of them is required'
+    end
+    # rubocop: enable Graphql/AuthorizeTypes
+  end
+end
diff --git a/app/graphql/types/notes/diff_position_input_type.rb b/app/graphql/types/notes/diff_position_input_type.rb
new file mode 100644
index 00000000000..02c91e173cb
--- /dev/null
+++ b/app/graphql/types/notes/diff_position_input_type.rb
@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+module Types
+  module Notes
+    # rubocop: disable Graphql/AuthorizeTypes
+    class DiffPositionInputType < DiffPositionBaseInputType
+      graphql_name 'DiffPositionInput'
+
+      argument :old_line, GraphQL::INT_TYPE, required: false,
+               description: copy_field_description(Types::Notes::DiffPositionType, :old_line)
+      argument :new_line, GraphQL::INT_TYPE, required: true,
+               description: copy_field_description(Types::Notes::DiffPositionType, :new_line)
+    end
+    # rubocop: enable Graphql/AuthorizeTypes
+  end
+end
diff --git a/changelogs/unreleased/62826-graphql-note-mutations.yml b/changelogs/unreleased/62826-graphql-note-mutations.yml
new file mode 100644
index 00000000000..85273186bb6
--- /dev/null
+++ b/changelogs/unreleased/62826-graphql-note-mutations.yml
@@ -0,0 +1,5 @@
+---
+title: GraphQL mutations for managing Notes
+merge_request: 30210
+author:
+type: added
diff --git a/spec/requests/api/graphql/mutations/notes/create/diff_note_spec.rb b/spec/requests/api/graphql/mutations/notes/create/diff_note_spec.rb
new file mode 100644
index 00000000000..b04fcb9aece
--- /dev/null
+++ b/spec/requests/api/graphql/mutations/notes/create/diff_note_spec.rb
@@ -0,0 +1,64 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe 'Adding a DiffNote' do
+  include GraphqlHelpers
+
+  set(:current_user) { create(:user) }
+  let(:noteable) { create(:merge_request, source_project: project, target_project: project) }
+  let(:project) { create(:project, :repository) }
+  let(:diff_refs) { noteable.diff_refs }
+  let(:mutation) do
+    variables = {
+      noteable_id: GitlabSchema.id_from_object(noteable).to_s,
+      body: 'Body text',
+      position: {
+        paths: {
+          old_path: 'files/ruby/popen.rb',
+          new_path: 'files/ruby/popen2.rb'
+        },
+        new_line: 14,
+        base_sha: diff_refs.base_sha,
+        head_sha: diff_refs.head_sha,
+        start_sha: diff_refs.start_sha
+      }
+    }
+
+    graphql_mutation(:create_diff_note, variables)
+  end
+
+  def mutation_response
+    graphql_mutation_response(:create_diff_note)
+  end
+
+  it_behaves_like 'a Note mutation when the user does not have permission'
+
+  context 'when the user has permission' do
+    before do
+      project.add_developer(current_user)
+    end
+
+    it_behaves_like 'a Note mutation that creates a Note'
+
+    it_behaves_like 'a Note mutation when there are active record validation errors', model: DiffNote
+
+    context do
+      let(:diff_refs) { build(:merge_request).diff_refs } # Allow fake diff refs so arguments are valid
+
+      it_behaves_like 'a Note mutation when the given resource id is not for a Noteable'
+    end
+
+    it 'returns the note with the correct position' do
+      post_graphql_mutation(mutation, current_user: current_user)
+
+      expect(mutation_response['note']['body']).to eq('Body text')
+      mutation_position_response = mutation_response['note']['position']
+      expect(mutation_position_response['positionType']).to eq('text')
+      expect(mutation_position_response['filePath']).to eq('files/ruby/popen2.rb')
+      expect(mutation_position_response['oldPath']).to eq('files/ruby/popen.rb')
+      expect(mutation_position_response['newPath']).to eq('files/ruby/popen2.rb')
+      expect(mutation_position_response['newLine']).to eq(14)
+    end
+  end
+end
diff --git a/spec/requests/api/graphql/mutations/notes/create/image_diff_note_spec.rb b/spec/requests/api/graphql/mutations/notes/create/image_diff_note_spec.rb
new file mode 100644
index 00000000000..3ba6c689024
--- /dev/null
+++ b/spec/requests/api/graphql/mutations/notes/create/image_diff_note_spec.rb
@@ -0,0 +1,70 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe 'Adding an image DiffNote' do
+  include GraphqlHelpers
+
+  set(:current_user) { create(:user) }
+  let(:noteable) { create(:merge_request, source_project: project, target_project: project) }
+  let(:project) { create(:project, :repository) }
+  let(:diff_refs) { noteable.diff_refs }
+  let(:mutation) do
+    variables = {
+      noteable_id: GitlabSchema.id_from_object(noteable).to_s,
+      body: 'Body text',
+      position: {
+        paths: {
+          old_path: 'files/images/any_image.png',
+          new_path: 'files/images/any_image2.png'
+        },
+        width: 100,
+        height: 200,
+        x: 1,
+        y: 2,
+        base_sha: diff_refs.base_sha,
+        head_sha: diff_refs.head_sha,
+        start_sha: diff_refs.start_sha
+      }
+    }
+
+    graphql_mutation(:create_image_diff_note, variables)
+  end
+
+  def mutation_response
+    graphql_mutation_response(:create_image_diff_note)
+  end
+
+  it_behaves_like 'a Note mutation when the user does not have permission'
+
+  context 'when the user has permission' do
+    before do
+      project.add_developer(current_user)
+    end
+
+    it_behaves_like 'a Note mutation that creates a Note'
+
+    it_behaves_like 'a Note mutation when there are active record validation errors', model: DiffNote
+
+    context do
+      let(:diff_refs) { build(:merge_request).diff_refs } # Allow fake diff refs so arguments are valid
+
+      it_behaves_like 'a Note mutation when the given resource id is not for a Noteable'
+    end
+
+    it 'returns the note with the correct position' do
+      post_graphql_mutation(mutation, current_user: current_user)
+
+      expect(mutation_response['note']['body']).to eq('Body text')
+      mutation_position_response = mutation_response['note']['position']
+      expect(mutation_position_response['filePath']).to eq('files/images/any_image2.png')
+      expect(mutation_position_response['oldPath']).to eq('files/images/any_image.png')
+      expect(mutation_position_response['newPath']).to eq('files/images/any_image2.png')
+      expect(mutation_position_response['positionType']).to eq('image')
+      expect(mutation_position_response['width']).to eq(100)
+      expect(mutation_position_response['height']).to eq(200)
+      expect(mutation_position_response['x']).to eq(1)
+      expect(mutation_position_response['y']).to eq(2)
+    end
+  end
+end
diff --git a/spec/requests/api/graphql/mutations/notes/create/note_spec.rb b/spec/requests/api/graphql/mutations/notes/create/note_spec.rb
new file mode 100644
index 00000000000..17aed69b650
--- /dev/null
+++ b/spec/requests/api/graphql/mutations/notes/create/note_spec.rb
@@ -0,0 +1,43 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe 'Adding a Note' do
+  include GraphqlHelpers
+
+  set(:current_user) { create(:user) }
+  let(:noteable) { create(:merge_request, source_project: project, target_project: project) }
+  let(:project) { create(:project, :repository) }
+  let(:mutation) do
+    variables = {
+      noteable_id: GitlabSchema.id_from_object(noteable).to_s,
+      body: 'Body text'
+    }
+
+    graphql_mutation(:create_note, variables)
+  end
+
+  def mutation_response
+    graphql_mutation_response(:create_note)
+  end
+
+  it_behaves_like 'a Note mutation when the user does not have permission'
+
+  context 'when the user has permission' do
+    before do
+      project.add_developer(current_user)
+    end
+
+    it_behaves_like 'a Note mutation that creates a Note'
+
+    it_behaves_like 'a Note mutation when there are active record validation errors'
+
+    it_behaves_like 'a Note mutation when the given resource id is not for a Noteable'
+
+    it 'returns the note' do
+      post_graphql_mutation(mutation, current_user: current_user)
+
+      expect(mutation_response['note']['body']).to eq('Body text')
+    end
+  end
+end
diff --git a/spec/requests/api/graphql/mutations/notes/destroy_spec.rb b/spec/requests/api/graphql/mutations/notes/destroy_spec.rb
new file mode 100644
index 00000000000..337a6e6f6e6
--- /dev/null
+++ b/spec/requests/api/graphql/mutations/notes/destroy_spec.rb
@@ -0,0 +1,52 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe 'Destroying a Note' do
+  include GraphqlHelpers
+
+  let!(:note) { create(:note) }
+  let(:mutation) do
+    variables = {
+      id: GitlabSchema.id_from_object(note).to_s
+    }
+
+    graphql_mutation(:destroy_note, variables)
+  end
+
+  def mutation_response
+    graphql_mutation_response(:destroy_note)
+  end
+
+  context 'when the user does not have permission' do
+    let(:current_user) { create(:user) }
+
+    it_behaves_like 'a mutation that returns top-level errors',
+                    errors: ['The resource that you are attempting to access does not exist or you don\'t have permission to perform this action']
+
+    it 'does not destroy the Note' do
+      expect do
+        post_graphql_mutation(mutation, current_user: current_user)
+      end.not_to change { Note.count }
+    end
+  end
+
+  context 'when the user has permission' do
+    let(:current_user) { note.author }
+
+    it_behaves_like 'a Note mutation when the given resource id is not for a Note'
+
+    it 'destroys the Note' do
+      expect do
+        post_graphql_mutation(mutation, current_user: current_user)
+      end.to change { Note.count }.by(-1)
+    end
+
+    it 'returns an empty Note' do
+      post_graphql_mutation(mutation, current_user: current_user)
+
+      expect(mutation_response).to have_key('note')
+      expect(mutation_response['note']).to be_nil
+    end
+  end
+end
diff --git a/spec/requests/api/graphql/mutations/notes/update_spec.rb b/spec/requests/api/graphql/mutations/notes/update_spec.rb
new file mode 100644
index 00000000000..958f640995a
--- /dev/null
+++ b/spec/requests/api/graphql/mutations/notes/update_spec.rb
@@ -0,0 +1,72 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe 'Updating a Note' do
+  include GraphqlHelpers
+
+  let!(:note) { create(:note, note: original_body) }
+  let(:original_body) { 'Initial body text' }
+  let(:updated_body) { 'Updated body text' }
+  let(:mutation) do
+    variables = {
+      id: GitlabSchema.id_from_object(note).to_s,
+      body: updated_body
+    }
+
+    graphql_mutation(:update_note, variables)
+  end
+
+  def mutation_response
+    graphql_mutation_response(:update_note)
+  end
+
+  context 'when the user does not have permission' do
+    let(:current_user) { create(:user) }
+
+    it_behaves_like 'a mutation that returns top-level errors',
+                    errors: ['The resource that you are attempting to access does not exist or you don\'t have permission to perform this action']
+
+    it 'does not update the Note' do
+      post_graphql_mutation(mutation, current_user: current_user)
+
+      expect(note.reload.note).to eq(original_body)
+    end
+  end
+
+  context 'when the user has permission' do
+    let(:current_user) { note.author }
+
+    it_behaves_like 'a Note mutation when the given resource id is not for a Note'
+
+    it 'updates the Note' do
+      post_graphql_mutation(mutation, current_user: current_user)
+
+      expect(note.reload.note).to eq(updated_body)
+    end
+
+    it 'returns the updated Note' do
+      post_graphql_mutation(mutation, current_user: current_user)
+
+      expect(mutation_response['note']['body']).to eq(updated_body)
+    end
+
+    context 'when there are ActiveRecord validation errors' do
+      let(:updated_body) { '' }
+
+      it_behaves_like 'a mutation that returns errors in the response', errors: ["Note can't be blank"]
+
+      it 'does not update the Note' do
+        post_graphql_mutation(mutation, current_user: current_user)
+
+        expect(note.reload.note).to eq(original_body)
+      end
+
+      it 'returns the Note with its original body' do
+        post_graphql_mutation(mutation, current_user: current_user)
+
+        expect(mutation_response['note']['body']).to eq(original_body)
+      end
+    end
+  end
+end
diff --git a/spec/support/helpers/graphql_helpers.rb b/spec/support/helpers/graphql_helpers.rb
index 1a09d48f4cd..ec3c460cd37 100644
--- a/spec/support/helpers/graphql_helpers.rb
+++ b/spec/support/helpers/graphql_helpers.rb
@@ -57,7 +57,8 @@ module GraphqlHelpers
   end
 
   def variables_for_mutation(name, input)
-    graphql_input = input.map { |name, value| [GraphqlHelpers.fieldnamerize(name), value] }.to_h
+    graphql_input = prepare_input_for_mutation(input)
+
     result = { input_variable_name_for_mutation(name) => graphql_input }
 
     # Avoid trying to serialize multipart data into JSON
@@ -68,6 +69,18 @@ module GraphqlHelpers
     end
   end
 
+  # Recursively convert a Hash with Ruby-style keys to GraphQL fieldname-style keys
+  #
+  # prepare_input_for_mutation({ 'my_key' => 1 })
+  #   => { 'myKey' => 1}
+  def prepare_input_for_mutation(input)
+    input.map do |name, value|
+      value = prepare_input_for_mutation(value) if value.is_a?(Hash)
+
+      [GraphqlHelpers.fieldnamerize(name), value]
+    end.to_h
+  end
+
   def input_variable_name_for_mutation(mutation_name)
     mutation_name = GraphqlHelpers.fieldnamerize(mutation_name)
     mutation_field = GitlabSchema.mutation.fields[mutation_name]
diff --git a/spec/support/shared_examples/graphql/notes_creation_shared_examples.rb b/spec/support/shared_examples/graphql/notes_creation_shared_examples.rb
new file mode 100644
index 00000000000..f2e1a95345b
--- /dev/null
+++ b/spec/support/shared_examples/graphql/notes_creation_shared_examples.rb
@@ -0,0 +1,61 @@
+# frozen_string_literal: true
+
+RSpec.shared_examples 'a Note mutation that does not create a Note' do
+  it do
+    expect do
+      post_graphql_mutation(mutation, current_user: current_user)
+    end.not_to change { Note.count }
+  end
+end
+
+RSpec.shared_examples 'a Note mutation that creates a Note' do
+  it do
+    expect do
+      post_graphql_mutation(mutation, current_user: current_user)
+    end.to change { Note.count }.by(1)
+  end
+end
+
+RSpec.shared_examples 'a Note mutation when the user does not have permission' do
+  it_behaves_like 'a Note mutation that does not create a Note'
+
+  it_behaves_like 'a mutation that returns top-level errors',
+                  errors: ['The resource that you are attempting to access does not exist or you don\'t have permission to perform this action']
+end
+
+RSpec.shared_examples 'a Note mutation when there are active record validation errors' do |model: Note|
+  before do
+    expect_next_instance_of(model) do |note|
+      expect(note).to receive(:valid?).at_least(:once).and_return(false)
+      expect(note).to receive_message_chain(
+        :errors,
+        :full_messages
+      ).and_return(['Error 1', 'Error 2'])
+    end
+  end
+
+  it_behaves_like 'a Note mutation that does not create a Note'
+
+  it_behaves_like 'a mutation that returns errors in the response', errors: ['Error 1', 'Error 2']
+
+  it 'returns an empty Note' do
+    post_graphql_mutation(mutation, current_user: current_user)
+
+    expect(mutation_response).to have_key('note')
+    expect(mutation_response['note']).to be_nil
+  end
+end
+
+RSpec.shared_examples 'a Note mutation when the given resource id is not for a Noteable' do
+  let(:noteable) { create(:label, project: project) }
+
+  it_behaves_like 'a Note mutation that does not create a Note'
+
+  it_behaves_like 'a mutation that returns top-level errors', errors: ['Cannot add notes to this resource']
+end
+
+RSpec.shared_examples 'a Note mutation when the given resource id is not for a Note' do
+  let(:note) { create(:issue) }
+
+  it_behaves_like 'a mutation that returns top-level errors', errors: ['Resource is not a note']
+end