Refactor to more robust implementation

In order to avoid string manipulation or modify route params (to make them unambiguous for `url_for`), we are accepting a small behavior change:

When being redirected to the canonical path for a group, if you requested a group show path starting with `/groups/…` then you’ll now be redirected to the group at root `/…`.

app/controllers/concerns/routable_actions.rb

@@ -32,19 +32,7 @@ module RoutableActions
       if canonical_path.casecmp(requested_full_path) != 0
         flash[:notice] = "#{routable.class.to_s.titleize} '#{requested_full_path}' was moved to '#{canonical_path}'. Please update any links and bookmarks that may still have the old path."
       end
-      redirect_to full_canonical_path(canonical_path, requested_full_path)
-    end
-  end
-
-  def full_canonical_path(canonical_path, requested_full_path)
-    request_path = request.original_fullpath
-    top_level_route_regex = %r{\A(/#{Regexp.union(DynamicPathValidator::TOP_LEVEL_ROUTES)}/)#{requested_full_path}}
-    top_level_route_match = request_path.match(top_level_route_regex)
-
-    if top_level_route_match
-      request_path.sub(top_level_route_regex, "\\1#{canonical_path}")
-    else
-      request_path.sub(requested_full_path, canonical_path)
+      redirect_to build_canonical_path(routable)
     end
   end
 end

app/controllers/groups/application_controller.rb

@@ -31,4 +31,14 @@ class Groups::ApplicationController < ApplicationController
       return render_403
     end
   end
+
+  def build_canonical_path(group)
+    if params[:group_id]
+      params[:group_id] = group.to_param
+    elsif params[:id]
+      params[:id] = group.to_param
+    end
+
+    url_for(params)
+  end
 end

app/controllers/groups_controller.rb

@@ -169,4 +169,9 @@ class GroupsController < Groups::ApplicationController
       @notification_setting = current_user.notification_settings_for(group)
     end
   end
+
+  def build_canonical_path(group)
+    return url_for(group) if action_name == 'show' # root group path
+    super
+  end
 end

app/controllers/projects/application_controller.rb

@@ -29,6 +29,18 @@ class Projects::ApplicationController < ApplicationController
     @project = find_routable!(Project, path, extra_authorization_proc: auth_proc)
   end
+  def build_canonical_path(project)
+    params[:namespace_id] = project.namespace.to_param
+
+    if params[:project_id]
+      params[:project_id] = project.to_param
+    elsif params[:id]
+      params[:id] = project.to_param
+    end
+
+    url_for(params)
+  end
+
   def repository
     @repository ||= project.repository
   end

app/controllers/users_controller.rb

@@ -138,4 +138,8 @@ class UsersController < ApplicationController
   def projects_for_current_user
     ProjectsFinder.new(current_user: current_user).execute
   end
+
+  def build_canonical_path(user)
+    url_for(params.merge(username: user.to_param))
+  end
 end

spec/controllers/groups/milestones_controller_spec.rb

@@ -21,7 +21,6 @@ describe Groups::MilestonesController do
     sign_in(user)
     group.add_owner(user)
     project.team << [user, :master]
-    controller.instance_variable_set(:@group, group)
   end
   it_behaves_like 'milestone tabs'
@@ -29,7 +28,7 @@ describe Groups::MilestonesController do
   describe "#create" do
     it "creates group milestone with Chinese title" do
       post :create,
-           group_id: group.id,
+           group_id: group.to_param,
            milestone: { project_ids: [project.id, project2.id], title: title }
       expect(response).to redirect_to(group_milestone_path(group, title.to_slug.to_s, title: title))
@@ -37,9 +36,139 @@ describe Groups::MilestonesController do
     end
     it "redirects to new when there are no project ids" do
-      post :create, group_id: group.id, milestone: { title: title, project_ids: [""] }
+      post :create, group_id: group.to_param, milestone: { title: title, project_ids: [""] }
       expect(response).to render_template :new
       expect(assigns(:milestone).errors).not_to be_nil
     end
   end
+
+  describe '#ensure_canonical_path' do
+    before do
+      sign_in(user)
+    end
+
+    context 'for a GET request' do
+      context 'when requesting the canonical path' do
+        context 'non-show path' do
+          context 'with exactly matching casing' do
+            it 'does not redirect' do
+              get :index, group_id: group.to_param
+
+              expect(response).not_to have_http_status(301)
+            end
+          end
+
+          context 'with different casing' do
+            it 'redirects to the correct casing' do
+              get :index, group_id: group.to_param.upcase
+
+              expect(response).to redirect_to(group_milestones_path(group.to_param))
+              expect(controller).not_to set_flash[:notice]
+            end
+          end
+        end
+
+        context 'show path' do
+          context 'with exactly matching casing' do
+            it 'does not redirect' do
+              get :show, group_id: group.to_param, id: title
+
+              expect(response).not_to have_http_status(301)
+            end
+          end
+
+          context 'with different casing' do
+            it 'redirects to the correct casing' do
+              get :show, group_id: group.to_param.upcase, id: title
+
+              expect(response).to redirect_to(group_milestone_path(group.to_param, title))
+              expect(controller).not_to set_flash[:notice]
+            end
+          end
+        end
+      end
+
+      context 'when requesting a redirected path' do
+        let(:redirect_route) { group.redirect_routes.create(path: 'old-path') }
+
+        it 'redirects to the canonical path' do
+          get :merge_requests, group_id: redirect_route.path, id: title
+
+          expect(response).to redirect_to(merge_requests_group_milestone_path(group.to_param, title))
+          expect(controller).to set_flash[:notice].to(group_moved_message(redirect_route, group))
+        end
+
+        context 'when the old group path is a substring of the scheme or host' do
+          let(:redirect_route) { group.redirect_routes.create(path: 'http') }
+
+          it 'does not modify the requested host' do
+            get :merge_requests, group_id: redirect_route.path, id: title
+
+            expect(response).to redirect_to(merge_requests_group_milestone_path(group.to_param, title))
+            expect(controller).to set_flash[:notice].to(group_moved_message(redirect_route, group))
+          end
+        end
+
+        context 'when the old group path is substring of groups' do
+          # I.e. /groups/oups should not become /grfoo/oups
+          let(:redirect_route) { group.redirect_routes.create(path: 'oups') }
+
+          it 'does not modify the /groups part of the path' do
+            get :merge_requests, group_id: redirect_route.path, id: title
+
+            expect(response).to redirect_to(merge_requests_group_milestone_path(group.to_param, title))
+            expect(controller).to set_flash[:notice].to(group_moved_message(redirect_route, group))
+          end
+        end
+
+        context 'when the old group path is substring of groups plus the new path' do
+          # I.e. /groups/oups/oup should not become /grfoos
+          let(:redirect_route) { group.redirect_routes.create(path: 'oups/oup') }
+
+          it 'does not modify the /groups part of the path' do
+            get :merge_requests, group_id: redirect_route.path, id: title
+
+            expect(response).to redirect_to(merge_requests_group_milestone_path(group.to_param, title))
+            expect(controller).to set_flash[:notice].to(group_moved_message(redirect_route, group))
+          end
+        end
+      end
+    end
+  end
+
+  context 'for a non-GET request' do
+    context 'when requesting the canonical path with different casing' do
+      it 'does not 404' do
+        post :create,
+             group_id: group.to_param,
+             milestone: { project_ids: [project.id, project2.id], title: title }
+
+        expect(response).not_to have_http_status(404)
+      end
+
+      it 'does not redirect to the correct casing' do
+        post :create,
+             group_id: group.to_param,
+             milestone: { project_ids: [project.id, project2.id], title: title }
+
+        expect(response).not_to have_http_status(301)
+      end
+    end
+
+    context 'when requesting a redirected path' do
+      let(:redirect_route) { group.redirect_routes.create(path: 'old-path') }
+
+      it 'returns not found' do
+        post :create,
+             group_id: redirect_route.path,
+             milestone: { project_ids: [project.id, project2.id], title: title }
+
+        expect(response).to have_http_status(404)
+      end
+    end
+  end
+
+  def group_moved_message(redirect_route, group)
+    "Group '#{redirect_route.path}' was moved to '#{group.full_path}'. Please update any links and bookmarks that may still have the old path."
+  end
 end

spec/controllers/groups_controller_spec.rb

@@ -214,12 +214,43 @@ describe GroupsController do
       end
       context 'when requesting groups under the /groups path' do
-        context 'when requesting the canonical path with different casing' do
-          it 'redirects to the correct casing' do
-            get :issues, id: group.to_param.upcase
-            expect(response).to redirect_to(issues_group_path(group.to_param))
-            expect(controller).not_to set_flash[:notice]
+        context 'when requesting the canonical path' do
+          context 'non-show path' do
+            context 'with exactly matching casing' do
+              it 'does not redirect' do
+                get :issues, id: group.to_param
+
+                expect(response).not_to have_http_status(301)
+              end
+            end
+            context 'with different casing' do
+              it 'redirects to the correct casing' do
+                get :issues, id: group.to_param.upcase
+
+                expect(response).to redirect_to(issues_group_path(group.to_param))
+                expect(controller).not_to set_flash[:notice]
+              end
+            end
+          end
+
+          context 'show path' do
+            context 'with exactly matching casing' do
+              it 'does not redirect' do
+                get :show, id: group.to_param
+
+                expect(response).not_to have_http_status(301)
+              end
+            end
+
+            context 'with different casing' do
+              it 'redirects to the correct casing at the root path' do
+                get :show, id: group.to_param.upcase
+
+                expect(response).to redirect_to(group)
+                expect(controller).not_to set_flash[:notice]
+              end
+            end
           end
         end

spec/support/milestone_tabs_examples.rb

 shared_examples 'milestone tabs' do
   def go(path, extra_params = {})
     params = if milestone.is_a?(GlobalMilestone)
-               { group_id: group.id, id: milestone.safe_title, title: milestone.title }
+               { group_id: group.to_param, id: milestone.safe_title, title: milestone.title }
              else
                { namespace_id: project.namespace.to_param, project_id: project, id: milestone.iid }
              end