Provide a Per-Page header

This header helps end users know, even if they are on a page that isn't
full, how many objects a single page may contain in the response. This
helps play nicely with some frontend pagination libraries that would
communicate with an API using api-pagination. Closes #26

Signed-off-by: David Celis <[email protected]>

Author: davidcelis

lib/grape/pagination.rb

@@ -19,8 +19,9 @@ def paginate(collection)
             links << %(<#{url}?#{new_params.to_param}>; rel="#{k}")
           end
 
-          header 'Link', links.join(', ') unless links.empty?
-          header 'Total', ApiPagination.total_from(collection)
+          header 'Link',     links.join(', ') unless links.empty?
+          header 'Total',    ApiPagination.total_from(collection)
+          header 'Per-Page', options[:per_page]
 
           return collection
         end

lib/rails/pagination.rb

@@ -39,11 +39,11 @@ def _paginate_collection(collection, options={})
         links << %(<#{url}?#{new_params.to_param}>; rel="#{k}")
       end
 
-      headers['Link']  = links.join(', ') unless links.empty?
-      headers['Total'] = ApiPagination.total_from(collection)
+      headers['Link']     = links.join(', ') unless links.empty?
+      headers['Total']    = ApiPagination.total_from(collection)
+      headers['Per-Page'] = options[:per_page]
 
       return collection
     end
   end
 end
-

spec/grape_spec.rb

@@ -8,9 +8,10 @@
   describe 'GET #index' do
     let(:links) { last_response.headers['Link'].split(', ') }
     let(:total) { last_response.headers['Total'].to_i }
+    let(:per_page) { last_response.headers['Per-Page'].to_i }
 
     context 'without enough items to give more than one page' do
-      before { get :numbers, :count => 10 }
+      before { get '/numbers', :count => 10 }
 
       it 'should not paginate' do
         expect(last_response.headers.keys).not_to include('Link')
@@ -20,33 +21,37 @@
         expect(total).to eq(10)
       end
 
+      it 'should give a Per-Page header' do
+        expect(per_page).to eq(10)
+      end
+
       it 'should list all numbers in the response body' do
         body = '[1,2,3,4,5,6,7,8,9,10]'
         expect(last_response.body).to eq(body)
       end
     end
 
     context 'with existing Link headers' do
-      before { get :numbers, :count => 30, :with_headers => true }
+      before { get '/numbers', :count => 30, :with_headers => true }
 
       it_behaves_like 'an endpoint with existing Link headers'
     end
 
     context 'with enough items to paginate' do
       context 'when on the first page' do
-        before { get :numbers, :count => 100 }
+        before { get '/numbers', :count => 100 }
 
         it_behaves_like 'an endpoint with a first page'
       end
 
       context 'when on the last page' do
-        before { get :numbers, :count => 100, :page => 10 }
+        before { get '/numbers', :count => 100, :page => 10 }
 
         it_behaves_like 'an endpoint with a last page'
       end
 
       context 'when somewhere comfortably in the middle' do
-        before { get :numbers, :count => 100, :page => 2 }
+        before { get '/numbers', :count => 100, :page => 2 }
 
         it_behaves_like 'an endpoint with a middle page'
       end

spec/rails_spec.rb

@@ -10,6 +10,7 @@
   describe 'GET #index' do
     let(:links) { response.headers['Link'].split(', ') }
     let(:total) { response.headers['Total'].to_i }
+    let(:per_page) { response.headers['Per-Page'].to_i }
 
     context 'without enough items to give more than one page' do
       before { get :index, :count => 10 }
@@ -22,6 +23,10 @@
         expect(total).to eq(10)
       end
 
+      it 'should give a Per-Page header' do
+        expect(per_page).to eq(10)
+      end
+
       it 'should list all numbers in the response body' do
         body = '[1,2,3,4,5,6,7,8,9,10]'
         expect(response.body).to eq(body)
@@ -65,8 +70,3 @@
     end
   end
 end
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