[API] Fix URLs in the 'Link' header for 'GET...

[API] Fix URLs in the 'Link' header for 'GET /projects/:id/repository/contributors' when no value is passed for 'order_by' or 'sort'
Signed-off-by: Rémy Coutable <remy@rymai.me>

changelogs/unreleased/45363-optional-params-on-api-endpoint-produce-invalid-pagination-header-links.yml

+---
+title: '[API] Fix URLs in the `Link` header for `GET /projects/:id/repository/contributors`
+  when no value is passed for `order_by` or `sort`'
+merge_request: 18393
+author:
+type: fixed

doc/api/repositories.md

@@ -183,7 +183,7 @@ GET /projects/:id/repository/contributors
 Parameters:
 
 - `id` (required) - The ID or [URL-encoded path of the project](README.md#namespaced-path-encoding) owned by the authenticated user
-- `order_by` (optional) - Return contributors ordered by `name`, `email`, or `commits` fields. If not given contributors are ordered by commit date.
+- `order_by` (optional) - Return contributors ordered by `name`, `email`, or `commits` (orders by commit date) fields. Default is `commits`
 - `sort` (optional) - Return contributors sorted in `asc` or `desc` order. Default is `asc`
 
 Response:

lib/api/repositories.rb

@@ -111,8 +111,8 @@ module API
       end
       params do
         use :pagination
-        optional :order_by, type: String, values: %w[email name commits], default: nil, desc: 'Return contributors ordered by `name` or `email` or `commits`'
-        optional :sort, type: String, values: %w[asc desc], default: nil, desc: 'Sort by asc (ascending) or desc (descending)'
+        optional :order_by, type: String, values: %w[email name commits], default: 'commits', desc: 'Return contributors ordered by `name` or `email` or `commits`'
+        optional :sort, type: String, values: %w[asc desc], default: 'asc', desc: 'Sort by asc (ascending) or desc (descending)'
       end
       get ':id/repository/contributors' do
         begin

spec/requests/api/repositories_spec.rb

@@ -427,5 +427,20 @@ describe API::Repositories do
         let(:request) { get api(route, guest) }
       end
     end
+
+    # Regression: https://gitlab.com/gitlab-org/gitlab-ce/issues/45363
+    describe 'Links header contains working URLs when no `order_by` nor `sort` is given' do
+      let(:project) { create(:project, :public, :repository) }
+      let(:current_user) { nil }
+
+      it 'returns `Link` header that includes URLs with default value for `order_by` & `sort`' do
+        get api(route, current_user)
+
+        first_link_url = response.headers['Link'].split(';').first
+
+        expect(first_link_url).to include('order_by=commits')
+        expect(first_link_url).to include('sort=asc')
+      end
+    end
   end
 end