Further refactoring for PageLimiter concern

Further simplifies the interface and removes some duplication.

app/controllers/concerns/page_limiter.rb

@@ -12,13 +12,13 @@
 #       end
 #
 #       # You can override the default response
-#       def page_out_of_bounds
+#       rescue_from PageOutOfBoundsError, with: :page_out_of_bounds
+#
+#       def page_out_of_bounds(error)
+#         # Page limit number is available as error.message
 #         head :ok
 #       end
 #
-#       # Or provide an entirely different handler:
-#       rescue_from PageOutOfBoundsError, with: :something
-#
 
 module PageLimiter
   extend ActiveSupport::Concern
@@ -29,39 +29,24 @@ module PageLimiter
   PageOutOfBoundsError      = Class.new(PageLimiterError)
 
   included do
-    attr_accessor :max_page_number
-    helper_method :max_page_number
-    rescue_from PageOutOfBoundsError, with: :page_out_of_bounds
-  end
-
-  def limit_pages(number)
-    set_max_page_number(number)
-    check_page_number
+    rescue_from PageOutOfBoundsError, with: :default_page_out_of_bounds_response
   end
 
-  # Override this method in your controller to customize the response
-  def page_out_of_bounds
-    default_page_out_of_bounds_response
+  def limit_pages(max_page_number)
+    check_page_number!(max_page_number)
   end
 
   private
 
-  def set_max_page_number(value)
-    raise PageLimitNotANumberError unless value.is_a?(Integer)
-    raise PageLimitNotSensibleError unless value > 0
-
-    self.max_page_number = value
-  end
+  # If the page exceeds the defined maximum, raise a PageOutOfBoundsError
+  # If the page doesn't exceed the limit, it does nothing.
+  def check_page_number!(max_page_number)
+    raise PageLimitNotANumberError unless max_page_number.is_a?(Integer)
+    raise PageLimitNotSensibleError unless max_page_number > 0
 
-  # If the page exceeds the defined maximum, either call the provided
-  # block (if provided) or call the #page_out_of_bounds method to
-  # provide a response.
-  #
-  # If the page doesn't exceed the limit, it yields the controller action.
-  def check_page_number
     if params[:page].present? && params[:page].to_i > max_page_number
-      record_interception
-      raise PageOutOfBoundsError
+      record_page_limit_interception
+      raise PageOutOfBoundsError.new(max_page_number)
     end
   end
 
@@ -71,7 +56,7 @@ module PageLimiter
   end
 
   # Record the page limit being hit in Prometheus
-  def record_interception
+  def record_page_limit_interception
     dd = DeviceDetector.new(request.user_agent)
 
     Gitlab::Metrics.counter(:gitlab_page_out_of_bounds,

app/controllers/explore/projects_controller.rb

@@ -10,6 +10,7 @@ class Explore::ProjectsController < Explore::ApplicationController
   before_action :set_non_archived_param
   before_action :set_sorting
 
+  # Limit taken from https://gitlab.com/gitlab-org/gitlab/issues/38357
   before_action only: [:index, :trending, :starred] do
     limit_pages(200)
   end
@@ -92,9 +93,9 @@ class Explore::ProjectsController < Explore::ApplicationController
     Project::SORTING_PREFERENCE_FIELD
   end
 
-  # Overrides the default in the PageLimiter concern
-  def page_out_of_bounds
+  def page_out_of_bounds(error)
     load_project_counts
+    @max_page_number = error.message
 
     respond_to do |format|
       format.html do

app/views/explore/projects/page_out_of_bounds.html.haml

@@ -18,4 +18,4 @@
       %h5= _("Maximum page reached")
       %p= _("Sorry, you have exceeded the maximum browsable page number. Please use the API to explore further.")
 
-      = link_to _("Back to page %{number}") % { number: max_page_number }, request.params.merge(page: max_page_number), class: 'btn btn-inverted'
+      = link_to _("Back to page %{number}") % { number: @max_page_number }, request.params.merge(page: @max_page_number), class: 'btn btn-inverted'

spec/controllers/concerns/page_limiter_spec.rb

@@ -57,7 +57,7 @@ describe PageLimiter do
 
       it "returns the expected result" do
         if result == PageLimiter::PageOutOfBoundsError
-          expect(instance).to receive(:record_interception)
+          expect(instance).to receive(:record_page_limit_interception)
           expect { subject }.to raise_error(result)
         elsif result&.superclass == PageLimiter::PageLimiterError
           expect { subject }.to raise_error(result)
@@ -68,18 +68,6 @@ describe PageLimiter do
     end
   end
 
-  describe "#page_out_of_bounds" do
-    subject { instance.page_out_of_bounds }
-
-    after do
-      subject
-    end
-
-    it "returns a bad_request header" do
-      expect(instance).to receive(:head).with(:bad_request)
-    end
-  end
-
   describe "#default_page_out_of_bounds_response" do
     subject { instance.send(:default_page_out_of_bounds_response) }
 
@@ -92,8 +80,8 @@ describe PageLimiter do
     end
   end
 
-  describe "#record_interception" do
-    subject { instance.send(:record_interception) }
+  describe "#record_page_limit_interception" do
+    subject { instance.send(:record_page_limit_interception) }
 
     it "records a metric counter" do
       expect(Gitlab::Metrics).to receive(:counter).with(

spec/controllers/explore/projects_controller_spec.rb

@@ -73,6 +73,10 @@ describe Explore::ProjectsController do
 
           it { is_expected.to respond_with(:bad_request) }
           it { is_expected.to render_template("explore/projects/page_out_of_bounds") }
+
+          it "assigns the page number" do
+            expect(assigns[:max_page_number]).to eq(page_limit.to_s)
+          end
         end
 
         describe "GET #{endpoint}.json" do