Add GraphQL Todoable interface for to-do targets

This adds a GraphQL interface called Todoable that is implemented by all
types that can be a target of a to-do item. These are:

- Issue
- Merge request
- Commit
- Epic
- Alert
- Design

This also adds a BatchCommitLoader to load commits of GraphQL objects at
a performance of O(1).

Changelog: added

app/graphql/types/alert_management/alert_type.rb

@@ -9,6 +9,7 @@ module Types
       present_using ::AlertManagement::AlertPresenter
 
       implements(Types::Notes::NoteableInterface)
+      implements(Types::TodoableInterface)
 
       authorize :read_alert_management_alert
 
@@ -127,6 +128,12 @@ module Types
             null: true,
             description: 'Alert condition for Prometheus.'
 
+      field :web_url,
+            GraphQL::Types::String,
+            method: :details_url,
+            null: false,
+            description: 'URL of the alert.'
+
       def notes
         object.ordered_notes
       end

app/graphql/types/commit_type.rb

@@ -8,6 +8,8 @@ module Types
 
     present_using CommitPresenter
 
+    implements(Types::TodoableInterface)
+
     field :id, type: GraphQL::Types::ID, null: false,
           description: 'ID (global ID) of the commit.'
 

app/graphql/types/design_management/design_type.rb

@@ -13,6 +13,12 @@ module Types
       implements(Types::Notes::NoteableInterface)
       implements(Types::DesignManagement::DesignFields)
       implements(Types::CurrentUserTodos)
+      implements(Types::TodoableInterface)
+
+      field :web_url,
+            GraphQL::Types::String,
+            null: false,
+            description: 'URL of the design.'
 
       field :versions,
             Types::DesignManagement::VersionType.connection_type,
@@ -40,6 +46,10 @@ module Types
       def request_cache_base_key
         self.class.name
       end
+
+      def web_url
+        Gitlab::UrlBuilder.build(object)
+      end
     end
   end
 end

app/graphql/types/issue_type.rb

@@ -8,6 +8,7 @@ module Types
 
     implements(Types::Notes::NoteableInterface)
     implements(Types::CurrentUserTodos)
+    implements(Types::TodoableInterface)
 
     authorize :read_issue
 

app/graphql/types/merge_request_type.rb

@@ -8,6 +8,7 @@ module Types
 
     implements(Types::Notes::NoteableInterface)
     implements(Types::CurrentUserTodos)
+    implements(Types::TodoableInterface)
 
     authorize :read_merge_request
 

app/graphql/types/todo_type.rb

@@ -31,6 +31,11 @@ module Types
           description: 'Action of the to-do item.',
           null: false
 
+    field :target, Types::TodoableInterface,
+          description: 'Target of the to-do item.',
+          calls_gitaly: true,
+          null: false
+
     field :target_type, Types::TodoTargetEnum,
           description: 'Target type of the to-do item.',
           null: false
@@ -59,5 +64,28 @@ module Types
     def author
       Gitlab::Graphql::Loaders::BatchModelLoader.new(User, object.author_id).find
     end
+
+    def target
+      if object.for_commit?
+        Gitlab::Graphql::Loaders::BatchCommitLoader.new(
+          container_class: Project,
+          container_id: object.project_id,
+          oid: object.commit_id
+        ).find
+      else
+        Gitlab::Graphql::Loaders::BatchModelLoader.new(target_type_class, object.target_id).find
+      end
+    end
+
+    private
+
+    def target_type_class
+      klass = object.target_type.safe_constantize
+      raise "Invalid target type \"#{object.target_type}\"" unless klass < Todoable
+
+      klass
+    end
   end
 end
+
+Types::TodoType.prepend_mod

app/graphql/types/todoable_interface.rb

+# frozen_string_literal: true
+
+module Types
+  module TodoableInterface
+    include Types::BaseInterface
+
+    graphql_name 'Todoable'
+
+    field :web_url, GraphQL::Types::String, null: true, description: 'URL of this object.'
+
+    def self.resolve_type(object, context)
+      case object
+      when Issue
+        Types::IssueType
+      when MergeRequest
+        Types::MergeRequestType
+      when ::DesignManagement::Design
+        Types::DesignManagement::DesignType
+      when ::AlertManagement::Alert
+        Types::AlertManagement::AlertType
+      when Commit
+        Types::CommitType
+      else
+        raise "Unknown GraphQL type for #{object}"
+      end
+    end
+  end
+end
+
+Types::TodoableInterface.prepend_mod

doc/api/graphql/reference/index.md

@@ -8595,6 +8595,7 @@ Describes an alert from the project's Alert Management.
 | <a id="alertmanagementalertstatus"></a>`status` | [`AlertManagementStatus`](#alertmanagementstatus) | Status of the alert. |
 | <a id="alertmanagementalerttitle"></a>`title` | [`String`](#string) | Title of the alert. |
 | <a id="alertmanagementalertupdatedat"></a>`updatedAt` | [`Time`](#time) | Timestamp the alert was last updated. |
+| <a id="alertmanagementalertweburl"></a>`webUrl` | [`String!`](#string) | URL of the alert. |
 
 #### Fields with arguments
 
@@ -9990,6 +9991,7 @@ A single design.
 | <a id="designnotes"></a>`notes` | [`NoteConnection!`](#noteconnection) | All notes on this noteable. (see [Connections](#connections)) |
 | <a id="designnotescount"></a>`notesCount` | [`Int!`](#int) | Total count of user-created notes for this design. |
 | <a id="designproject"></a>`project` | [`Project!`](#project) | Project the design belongs to. |
+| <a id="designweburl"></a>`webUrl` | [`String!`](#string) | URL of the design. |
 
 #### Fields with arguments
 
@@ -15898,6 +15900,7 @@ Representing a to-do entry.
 | <a id="todoid"></a>`id` | [`ID!`](#id) | ID of the to-do item. |
 | <a id="todoproject"></a>`project` | [`Project`](#project) | Project this to-do item is associated with. |
 | <a id="todostate"></a>`state` | [`TodoStateEnum!`](#todostateenum) | State of the to-do item. |
+| <a id="todotarget"></a>`target` | [`Todoable!`](#todoable) | Target of the to-do item. |
 | <a id="todotargettype"></a>`targetType` | [`TodoTargetEnum!`](#todotargetenum) | Target type of the to-do item. |
 
 ### `Topic`
@@ -19411,6 +19414,25 @@ Returns [`TimeboxReport`](#timeboxreport).
 | ---- | ---- | ----------- |
 | <a id="timeboxreportinterfacereportfullpath"></a>`fullPath` | [`String`](#string) | Full path of the project or group used as a scope for report. For example, `gitlab-org` or `gitlab-org/gitlab`. |
 
+#### `Todoable`
+
+Implementations:
+
+- [`AlertManagementAlert`](#alertmanagementalert)
+- [`BoardEpic`](#boardepic)
+- [`Commit`](#commit)
+- [`Design`](#design)
+- [`Epic`](#epic)
+- [`EpicIssue`](#epicissue)
+- [`Issue`](#issue)
+- [`MergeRequest`](#mergerequest)
+
+##### Fields
+
+| Name | Type | Description |
+| ---- | ---- | ----------- |
+| <a id="todoableweburl"></a>`webUrl` | [`String`](#string) | URL of this object. |
+
 #### `User`
 
 Representation of a GitLab user.

ee/app/graphql/ee/types/todoable_interface.rb

+# frozen_string_literal: true
+
+module EE
+  module Types
+    module TodoableInterface
+      extend ActiveSupport::Concern
+
+      class_methods do
+        extend ::Gitlab::Utils::Override
+
+        override :resolve_type
+        def resolve_type(object, *)
+          return ::Types::EpicType if Epic === object
+
+          super
+        end
+      end
+    end
+  end
+end

ee/app/graphql/types/epic_type.rb

@@ -17,6 +17,7 @@ module Types
     implements(Types::Notes::NoteableInterface)
     implements(Types::CurrentUserTodos)
     implements(Types::EventableType)
+    implements(Types::TodoableInterface)
 
     field :confidential, GraphQL::Types::Boolean, null: true,
           description: 'Indicates if the epic is confidential.'

ee/spec/graphql/ee/types/todoable_interface_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Types::TodoableInterface do
+  let(:extended_class) { Types::TodoableInterface }
+
+  describe ".resolve_type" do
+    it 'knows the correct type for EE-only objects' do
+      expect(extended_class.resolve_type(build(:epic), {})).to eq(Types::EpicType)
+    end
+  end
+end

ee/spec/graphql/types/epic_type_spec.rb

@@ -20,6 +20,8 @@ RSpec.describe GitlabSchema.types['Epic'] do
 
   it { expect(described_class.interfaces).to include(Types::CurrentUserTodos) }
 
+  it { expect(described_class.interfaces).to include(Types::TodoableInterface) }
+
   it { expect(described_class).to expose_permissions_using(Types::PermissionTypes::Epic) }
 
   it { expect(described_class.graphql_name).to eq('Epic') }

lib/gitlab/graphql/loaders/batch_commit_loader.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Graphql
+    module Loaders
+      class BatchCommitLoader
+        def initialize(container_class:, container_id:, oid:)
+          @container_class = container_class
+          @container_id = container_id
+          @oid = oid
+        end
+
+        def find
+          Gitlab::Graphql::Lazy.with_value(find_containers) do |container|
+            BatchLoader::GraphQL.for(oid).batch(key: container) do |oids, loader, args|
+              container = args[:key]
+
+              container.repository.commits_by(oids: oids).each do |commit|
+                loader.call(commit.id, commit) if commit
+              end
+            end
+          end
+        end
+
+        private
+
+        def find_containers
+          BatchLoader::GraphQL.for(container_id.to_i).batch(key: container_class) do |ids, loader, args|
+            model = args[:key]
+            results = model.includes(:route).id_in(ids) # rubocop: disable CodeReuse/ActiveRecord
+
+            results.each { |record| loader.call(record.id, record) }
+          end
+        end
+
+        attr_reader :container_class, :container_id, :oid
+      end
+    end
+  end
+end

spec/graphql/types/alert_management/alert_type_spec.rb

@@ -7,6 +7,8 @@ RSpec.describe GitlabSchema.types['AlertManagementAlert'] do
 
   specify { expect(described_class).to require_graphql_authorizations(:read_alert_management_alert) }
 
+  specify { expect(described_class.interfaces).to include(Types::TodoableInterface) }
+
   it 'exposes the expected fields' do
     expected_fields = %i[
       iid
@@ -34,6 +36,7 @@ RSpec.describe GitlabSchema.types['AlertManagementAlert'] do
       details_url
       prometheus_alert
       environment
+      web_url
     ]
 
     expect(described_class).to have_graphql_fields(*expected_fields)

spec/graphql/types/commit_type_spec.rb

@@ -7,6 +7,8 @@ RSpec.describe GitlabSchema.types['Commit'] do
 
   specify { expect(described_class).to require_graphql_authorizations(:download_code) }
 
+  specify { expect(described_class).to include(Types::TodoableInterface) }
+
   it 'contains attributes related to commit' do
     expect(described_class).to have_graphql_fields(
       :id, :sha, :short_id, :title, :full_title, :full_title_html, :description, :description_html, :message, :title_html, :authored_date,

spec/graphql/types/design_management/design_type_spec.rb

@@ -5,8 +5,10 @@ require 'spec_helper'
 RSpec.describe GitlabSchema.types['Design'] do
   specify { expect(described_class.interfaces).to include(Types::CurrentUserTodos) }
 
+  specify { expect(described_class.interfaces).to include(Types::TodoableInterface) }
+
   it_behaves_like 'a GraphQL type with design fields' do
-    let(:extra_design_fields) { %i[notes current_user_todos discussions versions] }
+    let(:extra_design_fields) { %i[notes current_user_todos discussions versions web_url] }
     let_it_be(:design) { create(:design, :with_versions) }
     let(:object_id) { GitlabSchema.id_from_object(design) }
     let_it_be(:object_id_b) { GitlabSchema.id_from_object(create(:design, :with_versions)) }

spec/graphql/types/merge_request_type_spec.rb

@@ -13,6 +13,8 @@ RSpec.describe GitlabSchema.types['MergeRequest'] do
 
   specify { expect(described_class.interfaces).to include(Types::CurrentUserTodos) }
 
+  specify { expect(described_class.interfaces).to include(Types::TodoableInterface) }
+
   it 'has the expected fields' do
     expected_fields = %w[
       notes discussions user_permissions id iid title title_html description

spec/graphql/types/todo_type_spec.rb

@@ -4,7 +4,7 @@ require 'spec_helper'
 
 RSpec.describe GitlabSchema.types['Todo'] do
   it 'has the correct fields' do
-    expected_fields = [:id, :project, :group, :author, :action, :target_type, :body, :state, :created_at]
+    expected_fields = [:id, :project, :group, :author, :action, :target, :target_type, :body, :state, :created_at]
 
     expect(described_class).to have_graphql_fields(*expected_fields)
   end

spec/graphql/types/todoable_interface_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Types::TodoableInterface do
+  it 'exposes the expected fields' do
+    expected_fields = %i[
+      web_url
+    ]
+
+    expect(described_class).to have_graphql_fields(*expected_fields)
+  end
+
+  describe ".resolve_type" do
+    it 'knows the correct type for objects' do
+      expect(described_class.resolve_type(build(:issue), {})).to eq(Types::IssueType)
+      expect(described_class.resolve_type(build(:merge_request), {})).to eq(Types::MergeRequestType)
+      expect(described_class.resolve_type(build(:design), {})).to eq(Types::DesignManagement::DesignType)
+      expect(described_class.resolve_type(build(:alert_management_alert), {})).to eq(Types::AlertManagement::AlertType)
+      expect(described_class.resolve_type(build(:commit), {})).to eq(Types::CommitType)
+    end
+
+    it 'raises an error for an unknown type' do
+      project = build(:project)
+
+      expect { described_class.resolve_type(project, {}) }.to raise_error("Unknown GraphQL type for #{project}")
+    end
+  end
+end

spec/lib/gitlab/graphql/loaders/batch_commit_loader_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::Graphql::Loaders::BatchCommitLoader do
+  include RepoHelpers
+
+  describe '#find' do
+    let_it_be(:first_project) { create(:project, :repository) }
+    let_it_be(:second_project) { create(:project, :repository) }
+
+    let_it_be(:first_commit) { first_project.commit(sample_commit.id) }
+    let_it_be(:second_commit) { first_project.commit(another_sample_commit.id) }
+    let_it_be(:third_commit) { second_project.commit(sample_big_commit.id) }
+
+    it 'finds a commit by id' do
+      result = described_class.new(
+        container_class: Project,
+        container_id: first_project.id,
+        oid: first_commit.id
+      ).find
+
+      expect(result.force).to eq(first_commit)
+    end
+
+    before do
+      ActiveSupport::Notifications.subscribe('sql.active_record') do |event|
+        raise "no!" if event.payload[:sql].include?('SELECT "namespaces".')
+      end
+    end
+
+    it 'only queries once' do
+      expect do
+        [
+          described_class.new(
+            container_class: Project,
+            container_id: first_project.id,
+            oid: first_commit.id
+          ).find,
+          described_class.new(
+            container_class: Project,
+            container_id: first_project.id,
+            oid: second_commit.id
+          ).find,
+          described_class.new(
+            container_class: Project,
+            container_id: second_project.id,
+            oid: third_commit.id
+          ).find
+        ].map(&:force)
+      end.not_to exceed_query_limit(2)
+    end
+  end
+end