Add commit diffs to commit object on graphql

Added diffs to commit endpoint, similar to "GET
/projects/:id/repository/commits/:sha/diff";
Added Graphql diffs type;
Changelog: added

Signed-off-by: Lucas Zampieri <lzampier@redhat.com>

app/graphql/types/commit_type.rb

@@ -59,6 +59,14 @@ class CommitType < BaseObject
     field :author, type: Types::UserType, null: true,
                    description: 'Author of the commit.'
 
+    field :diffs, [Types::DiffType], null: true, calls_gitaly: true,
+    description: 'Diffs contained within the commit. ' \
+                 'This field can only be resolved for 10 diffs in any single request.' do
+      # Limited to 10 calls per GraphQL request as calling `diffs` multiple times will
+      # lead to N+1 queries to Gitaly.
+      extension ::Gitlab::Graphql::Limit::FieldCallCount, limit: 10
+    end
+
     field :pipelines,
           null: true,
           description: 'Pipelines of the commit ordered latest first.',
@@ -68,6 +76,10 @@ class CommitType < BaseObject
     markdown_field :full_title_html, null: true
     markdown_field :description_html, null: true
 
+    def diffs
+      object.diffs.diffs
+    end
+
     def author_gravatar
       GravatarService.new.execute(object.author_email, 40)
     end

app/graphql/types/diff_type.rb

+# frozen_string_literal: true
+
+module Types
+  # rubocop: disable Graphql/AuthorizeTypes
+  class DiffType < BaseObject
+    graphql_name 'Diff'
+
+    field :a_mode, GraphQL::Types::String, null: true,
+      description: 'Old file mode of the file.'
+    field :b_mode, GraphQL::Types::String, null: true,
+      description: 'New file mode of the file.'
+    field :deleted_file, GraphQL::Types::String, null: true,
+      description: 'Indicates if the file has been removed. '
+    field :diff, GraphQL::Types::String, null: true,
+      description: 'Diff representation of the changes made to the file.'
+    field :new_file, GraphQL::Types::String, null: true,
+      description: 'Indicates if the file has just been added. '
+    field :new_path, GraphQL::Types::String, null: true,
+      description: 'New path of the file.'
+    field :old_path, GraphQL::Types::String, null: true,
+      description: 'Old path of the file.'
+    field :renamed_file, GraphQL::Types::String, null: true,
+      description: 'Indicates if the file has been renamed.'
+  end
+  # rubocop: enable Graphql/AuthorizeTypes
+end

doc/api/graphql/reference/index.md

@@ -13194,6 +13194,7 @@ Code Quality report for a pipeline.
 | <a id="commitauthoreddate"></a>`authoredDate` | [`Time`](#time) | Timestamp of when the commit was authored. |
 | <a id="commitdescription"></a>`description` | [`String`](#string) | Description of the commit message. |
 | <a id="commitdescriptionhtml"></a>`descriptionHtml` | [`String`](#string) | GitLab Flavored Markdown rendering of `description`. |
+| <a id="commitdiffs"></a>`diffs` | [`[Diff!]`](#diff) | Diffs contained within the commit. This field can only be resolved for 10 diffs in any single request. |
 | <a id="commitfulltitle"></a>`fullTitle` | [`String`](#string) | Full title of the commit message. |
 | <a id="commitfulltitlehtml"></a>`fullTitleHtml` | [`String`](#string) | GitLab Flavored Markdown rendering of `full_title`. |
 | <a id="commitid"></a>`id` | [`ID!`](#id) | ID (global ID) of the commit. |
@@ -14366,6 +14367,21 @@ Snapshot.
 | <a id="devopsadoptionsnapshottotalprojectscount"></a>`totalProjectsCount` | [`Int`](#int) | Total number of projects. |
 | <a id="devopsadoptionsnapshotvulnerabilitymanagementusedcount"></a>`vulnerabilityManagementUsedCount` | [`Int`](#int) | Total number of projects with vulnerability management used at least once. |
+### `Diff`
+
+#### Fields
+
+| Name | Type | Description |
+| ---- | ---- | ----------- |
+| <a id="diffamode"></a>`aMode` | [`String`](#string) | Old file mode of the file. |
+| <a id="diffbmode"></a>`bMode` | [`String`](#string) | New file mode of the file. |
+| <a id="diffdeletedfile"></a>`deletedFile` | [`String`](#string) | Indicates if the file has been removed. |
+| <a id="diffdiff"></a>`diff` | [`String`](#string) | Diff representation of the changes made to the file. |
+| <a id="diffnewfile"></a>`newFile` | [`String`](#string) | Indicates if the file has just been added. |
+| <a id="diffnewpath"></a>`newPath` | [`String`](#string) | New path of the file. |
+| <a id="diffoldpath"></a>`oldPath` | [`String`](#string) | Old path of the file. |
+| <a id="diffrenamedfile"></a>`renamedFile` | [`String`](#string) | Indicates if the file has been renamed. |
+
 ### `DiffPosition`
 #### Fields

spec/graphql/types/commit_type_spec.rb

@@ -12,8 +12,14 @@
   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,
-      :author_name, :author_email, :author_gravatar, :author, :web_url, :web_path,
+      :author_name, :author_email, :author_gravatar, :author, :diffs, :web_url, :web_path,
       :pipelines, :signature_html, :signature
     )
   end
+
+  describe 'diffs' do
+    it 'limits field call count' do
+      expect(described_class.fields['diffs'].extensions).to include(a_kind_of(::Gitlab::Graphql::Limit::FieldCallCount))
+    end
+  end
 end

spec/graphql/types/diff_type_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe GitlabSchema.types['Diff'], feature_category: :code_review_workflow do
+  include RepoHelpers
+  include GraphqlHelpers
+
+  specify { expect(described_class.graphql_name).to eq('Diff') }
+
+  it 'contains attributes related to diff' do
+    expect(described_class).to have_graphql_fields(
+      :a_mode, :b_mode, :deleted_file, :diff, :new_file, :new_path, :old_path, :renamed_file
+    )
+  end
+
+  describe '#diff' do
+    subject { resolve_field(:diff, diff, object_type: described_class) }
+
+    let(:merge_request_diff) { create(:merge_request).merge_request_diff }
+    let(:diff) { merge_request_diff.diffs.diffs.first }
+
+    it 'returns the diff of the passed commit' do
+      is_expected.to eq(diff.diff)
+    end
+  end
+end