Merge branch...

Merge branch '18140-add-to-next-and-previous-commit-buttons-when-viewing-commits-in-merge-request' into 'master'

Add previous and next commit IDs to the diffs JSON response

Closes #18140

See merge request gitlab-org/gitlab!27528

app/serializers/diffs_entity.rb

@@ -16,12 +16,7 @@ class DiffsEntity < Grape::Entity
   end
 
   expose :commit do |diffs, options|
-    CommitEntity.represent options[:commit], options.merge(
-      type: :full,
-      commit_url_params: { merge_request_iid: merge_request&.iid },
-      pipeline_ref: merge_request&.source_branch,
-      pipeline_project: merge_request&.source_project
-    )
+    CommitEntity.represent(options[:commit], commit_options(options))
   end
 
   expose :context_commits, using: API::Entities::Commit, if: -> (diffs, options) { merge_request&.project&.context_commits_enabled? } do |diffs|
@@ -88,4 +83,31 @@ class DiffsEntity < Grape::Entity
   def merge_request
     options[:merge_request]
   end
+
+  private
+
+  def commit_ids
+    @commit_ids ||= merge_request.recent_commits.map(&:id)
+  end
+
+  def commit_neighbors(commit_id)
+    index = commit_ids.index(commit_id)
+
+    return [] unless index
+
+    [(index > 0 ? commit_ids[index - 1] : nil), commit_ids[index + 1]]
+  end
+
+  def commit_options(options)
+    prev_commit_id, next_commit_id = *commit_neighbors(options[:commit]&.id)
+
+    options.merge(
+      type: :full,
+      commit_url_params: { merge_request_iid: merge_request&.iid },
+      pipeline_ref: merge_request&.source_branch,
+      pipeline_project: merge_request&.source_project,
+      prev_commit_id: prev_commit_id,
+      next_commit_id: next_commit_id
+    )
+  end
 end

lib/api/entities/commit_with_link.rb

@@ -32,6 +32,14 @@ module API
         render('projects/commit/_signature', signature: commit.signature) if commit.has_signature?
       end
 
+      expose :prev_commit_id, if: { type: :full } do |commit|
+        options[:prev_commit_id]
+      end
+
+      expose :next_commit_id, if: { type: :full } do |commit|
+        options[:next_commit_id]
+      end
+
       expose :pipeline_status_path, if: { type: :full } do |commit, options|
         pipeline_ref = options[:pipeline_ref]
         pipeline_project = options[:pipeline_project] || commit.project

spec/serializers/diffs_entity_spec.rb

@@ -26,5 +26,47 @@ describe DiffsEntity do
         :merge_request_diffs, :definition_path_prefix
       )
     end
+
+    context "when a commit_id is passed" do
+      let(:commits) { merge_request.commits }
+      let(:entity) do
+        described_class.new(
+          merge_request_diffs.first.diffs,
+          request: request,
+          merge_request: merge_request,
+          merge_request_diffs: merge_request_diffs,
+          commit: commit
+        )
+      end
+
+      subject { entity.as_json }
+
+      context "when the passed commit is not the first or last in the group" do
+        let(:commit) { commits.third }
+
+        it 'includes commit references for previous and next' do
+          expect(subject[:commit][:prev_commit_id]).to eq(commits.second.id)
+          expect(subject[:commit][:next_commit_id]).to eq(commits.fourth.id)
+        end
+      end
+
+      context "when the passed commit is the first in the group" do
+        let(:commit) { commits.first }
+
+        it 'includes commit references for nil and next' do
+          expect(subject[:commit][:prev_commit_id]).to be_nil
+          expect(subject[:commit][:next_commit_id]).to eq(commits.second.id)
+        end
+      end
+
+      context "when the passed commit is the last in the group" do
+        let(:commit) { commits.last }
+
+        it 'includes commit references for previous and nil' do
+          expect(subject[:commit][:prev_commit_id]).to eq(commits[-2].id)
+          expect(subject[:commit][:next_commit_id]).to be_nil
+        end
+      end
+    end
   end
 end