Merge branch 'fix/pagination-link' into 'master'

fix(api): include standard Link header in keyset pagination

Closes #218504

See merge request gitlab-org/gitlab!33714

changelogs/unreleased/fix-pagination-link.yml

+---
+title: Fix pagination link header
+merge_request: 33714
+author: Max Wittig
+type: fixed

doc/api/README.md

@@ -417,10 +417,14 @@ The response header includes a link to the next page. For example:
 HTTP/1.1 200 OK
 ...
 Links: <https://gitlab.example.com/api/v4/projects?pagination=keyset&per_page=50&order_by=id&sort=asc&id_after=42>; rel="next"
+Link: <https://gitlab.example.com/api/v4/projects?pagination=keyset&per_page=50&order_by=id&sort=asc&id_after=42>; rel="next"
 Status: 200 OK
 ...
 ```
 
+CAUTION: **Deprecation:**
+The `Links` Header will be removed in GitLab 14.0 to be aligned with the [W3C specification](https://www.w3.org/wiki/LinkHeader)
+
 The link to the next page contains an additional filter `id_after=42` which excludes records we have retrieved already.
 Note the type of filter depends on the `order_by` option used and we may have more than one additional filter.
 

lib/gitlab/pagination/keyset/request_context.rb

@@ -24,7 +24,9 @@ module Gitlab
         end
 
         def apply_headers(next_page)
-          request.header('Links', pagination_links(next_page))
+          link = pagination_links(next_page)
+          request.header('Links', link)
+          request.header('Link', link)
         end
 
         private

spec/lib/gitlab/pagination/keyset/request_context_spec.rb

@@ -60,9 +60,7 @@ describe Gitlab::Pagination::Keyset::RequestContext do
     it 'sets Links header with same host/path as the original request' do
       orig_uri = URI.parse(request_context.request.url)
 
-      expect(request_context).to receive(:header) do |name, header|
-        expect(name).to eq('Links')
-
+      expect(request_context).to receive(:header).twice do |name, header|
         first_link, _ = /<([^>]+)>; rel="next"/.match(header).captures
 
         uri = URI.parse(first_link)
@@ -77,9 +75,7 @@ describe Gitlab::Pagination::Keyset::RequestContext do
     it 'sets Links header with a link to the next page' do
       orig_uri = URI.parse(request_context.request.url)
 
-      expect(request_context).to receive(:header) do |name, header|
-        expect(name).to eq('Links')
-
+      expect(request_context).to receive(:header).twice do |name, header|
         first_link, _ = /<([^>]+)>; rel="next"/.match(header).captures
 
         query = CGI.parse(URI.parse(first_link).query)
@@ -97,9 +93,7 @@ describe Gitlab::Pagination::Keyset::RequestContext do
       it 'sets Links header with a link to the next page' do
         orig_uri = URI.parse(request_context.request.url)
 
-        expect(request_context).to receive(:header) do |name, header|
-          expect(name).to eq('Links')
-
+        expect(request_context).to receive(:header).twice do |name, header|
           first_link, _ = /<([^>]+)>; rel="next"/.match(header).captures
 
           query = CGI.parse(URI.parse(first_link).query)

spec/requests/api/projects_spec.rb

@@ -597,6 +597,10 @@ describe API::Projects do
           expect(response.header).to include('Links')
           expect(response.header['Links']).to include('pagination=keyset')
           expect(response.header['Links']).to include("id_after=#{public_project.id}")
+
+          expect(response.header).to include('Link')
+          expect(response.header['Link']).to include('pagination=keyset')
+          expect(response.header['Link']).to include("id_after=#{public_project.id}")
         end
 
         it 'contains only the first project with per_page = 1' do
@@ -613,12 +617,17 @@ describe API::Projects do
           expect(response.header).to include('Links')
           expect(response.header['Links']).to include('pagination=keyset')
           expect(response.header['Links']).to include("id_after=#{project3.id}")
+
+          expect(response.header).to include('Link')
+          expect(response.header['Link']).to include('pagination=keyset')
+          expect(response.header['Link']).to include("id_after=#{project3.id}")
         end
 
         it 'does not include a next link when the page does not have any records' do
           get api('/projects', current_user), params: params.merge(id_after: Project.maximum(:id))
 
           expect(response.header).not_to include('Links')
+          expect(response.header).not_to include('Link')
         end
 
         it 'returns an empty array when the page does not have any records' do
@@ -644,6 +653,10 @@ describe API::Projects do
           expect(response.header).to include('Links')
           expect(response.header['Links']).to include('pagination=keyset')
           expect(response.header['Links']).to include("id_before=#{project3.id}")
+
+          expect(response.header).to include('Link')
+          expect(response.header['Link']).to include('pagination=keyset')
+          expect(response.header['Link']).to include("id_before=#{project3.id}")
         end
 
         it 'contains only the last project with per_page = 1' do
@@ -672,6 +685,11 @@ describe API::Projects do
               match[1]
             end
 
+            link = response.header['Link']
+            url = link&.match(/<[^>]+(\/projects\?[^>]+)>; rel="next"/) do |match|
+              match[1]
+            end
+
             ids += Gitlab::Json.parse(response.body).map { |p| p['id'] }
           end