Handle out of bound batch request gracefully

app/models/merge_request_diff.rb

@@ -393,8 +393,10 @@ class MergeRequestDiff < ApplicationRecord
       diffs_batch = diffs_in_batch_collection(batch_page, batch_size, diff_options: diff_options)
 
       if comparison
+        if diff_options[:paths].blank? && !without_files?
+          # Return the empty MergeRequestDiffBatch for an out of bound batch request
+          break diffs_batch if diffs_batch.diff_file_paths.blank?
 
-        if diff_options[:paths].blank? && !without_files? && diffs_batch.diff_file_paths.present?
           diff_options.merge!(
             paths: diffs_batch.diff_file_paths,
             pagination_data: diffs_batch.pagination_data

lib/gitlab/diff/file_collection/merge_request_diff_batch.rb

@@ -21,9 +21,9 @@ module Gitlab
           @paginated_collection = load_paginated_collection(batch_page, batch_size, diff_options)
 
           @pagination_data = {
-            current_page: batch_gradual_load? ? nil : @paginated_collection.current_page,
-            next_page: batch_gradual_load? ? nil : @paginated_collection.next_page,
-            total_pages: batch_gradual_load? ? relation.size : @paginated_collection.total_pages
+            current_page: current_page,
+            next_page: next_page,
+            total_pages: total_pages
           }
         end
 
@@ -62,6 +62,24 @@ module Gitlab
           @merge_request_diff.merge_request_diff_files
         end
 
+        def current_page
+          return if @paginated_collection.blank?
+
+          batch_gradual_load? ? nil : @paginated_collection.current_page
+        end
+
+        def next_page
+          return if @paginated_collection.blank?
+
+          batch_gradual_load? ? nil : @paginated_collection.next_page
+        end
+
+        def total_pages
+          return if @paginated_collection.blank?
+
+          batch_gradual_load? ? relation.size : @paginated_collection.total_pages
+        end
+
         # rubocop: disable CodeReuse/ActiveRecord
         def load_paginated_collection(batch_page, batch_size, diff_options)
           batch_page ||= DEFAULT_BATCH_PAGE

spec/models/merge_request_diff_spec.rb

@@ -499,6 +499,14 @@ RSpec.describe MergeRequestDiff do
             expect(diffs.pagination_data).to eq(current_page: 1, next_page: 2, total_pages: 2)
           end
 
+          it 'returns an empty MergeRequestBatch with empty pagination data when the batch is empty' do
+            diffs = diff_with_commits.diffs_in_batch(3, 10, diff_options: diff_options)
+
+            expect(diffs).to be_a(Gitlab::Diff::FileCollection::MergeRequestDiffBatch)
+            expect(diffs.diff_files.size).to eq 0
+            expect(diffs.pagination_data).to eq(current_page: nil, next_page: nil, total_pages: nil)
+          end
+
           context 'with gradual load enabled' do
             before do
               stub_feature_flags(diffs_gradual_load: true)
@@ -512,6 +520,14 @@ RSpec.describe MergeRequestDiff do
               expect(diffs.diff_files.size).to eq 10
               expect(diffs.pagination_data).to eq(current_page: nil, next_page: nil, total_pages: file_count)
             end
+
+            it 'returns an empty MergeRequestBatch with empty pagination data when the batch is empty' do
+              diffs = diff_with_commits.diffs_in_batch(30, 10, diff_options: diff_options)
+
+              expect(diffs).to be_a(Gitlab::Diff::FileCollection::MergeRequestDiffBatch)
+              expect(diffs.diff_files.size).to eq 0
+              expect(diffs.pagination_data).to eq(current_page: nil, next_page: nil, total_pages: nil)
+            end
           end
         end
       end