Redirect API requests for merged page to new page

Author: Mr0grog

app/controllers/api/v0/pages_controller.rb

@@ -71,7 +71,16 @@ def index
   end
 
   def show
-    page = Page.find(params[:id])
+    begin
+      page = Page.find(params[:id])
+    rescue ActiveRecord::RecordNotFound
+      merge = MergedPage.find(params[:id])
+      redirect_to(
+        api_v0_page_url(merge.target_uuid),
+        status: :permanent_redirect
+      ) and return
+    end
+
     data = page.as_json(include: [:maintainers, :tags])
     if should_allow_versions
       data['versions'] = page.versions.where(different: true).as_json

test/controllers/api/v0/pages_controller_test.rb

@@ -744,4 +744,15 @@ def get_all_pages(url)
     body = JSON.parse(@response.body)
     assert(body['data'].all? {|page| page['status'] >= 400 && page['status'] < 500})
   end
+
+  test 'redirects to new page if requested page was merged away' do
+    page1 = Page.create(title: 'First Page', url: 'https://example.gov/')
+    page2 = Page.create(title: 'Second Page', url: 'https://example.gov/subpage')
+    page1.merge(page2)
+
+    sign_in users(:alice)
+    get(api_v0_page_url(page2))
+    assert_response(:permanent_redirect)
+    assert_redirected_to(api_v0_page_url(page1.uuid))
+  end
 end