Cache only cacheable status codes

lib/faraday_middleware/response/caching.rb

@@ -7,6 +7,15 @@ module FaradayMiddleware
   # Public: Caches GET responses and pulls subsequent ones from the cache.
   class Caching < Faraday::Middleware
     attr_reader :cache
+    # Internal: List of status codes that can be cached:
+    # * 200 - 'OK'
+    # * 203 - 'Non-Authoritative Information'
+    # * 300 - 'Multiple Choices'
+    # * 301 - 'Moved Permanently'
+    # * 302 - 'Found'
+    # * 404 - 'Not Found'
+    # * 410 - 'Gone'
+    CACHEABLE_STATUS_CODES = [200, 203, 300, 301, 302, 404, 410]
 
     extend Forwardable
     def_delegators :'Faraday::Utils', :parse_query, :build_query
@@ -34,7 +43,14 @@ def call(env)
           cache_on_complete(env)
         else
           # synchronous mode
-          response = cache.fetch(cache_key(env)) { @app.call(env) }
+          key = cache_key(env)
+          unless response = cache.read(key) and response
+            response = @app.call(env)
+
+            if CACHEABLE_STATUS_CODES.include?(response.status)
+              cache.write(key, response)
+            end
+          end
           finalize_response(response, env)
         end
       else
@@ -63,7 +79,9 @@ def cache_on_complete(env)
         finalize_response(cached_response, env)
       else
         response = @app.call(env)
-        response.on_complete { cache.write(key, response) }
+        if CACHEABLE_STATUS_CODES.include?(response.status)
+          response.on_complete { cache.write(key, response) }
+        end
       end
     end
 

spec/caching_spec.rb

@@ -13,7 +13,9 @@
     response = lambda { |env|
       [200, {'Content-Type' => 'text/plain'}, "request:#{request_count+=1}"]
     }
-
+    broken = lambda { |env|
+      [500, {'Content-Type' => 'text/plain'}, "request:#{request_count+=1}"]
+    }
     @conn = Faraday.new do |b|
       b.use CachingLint
       b.use FaradayMiddleware::Caching, @cache, options
@@ -22,6 +24,7 @@
         stub.get('/?foo=bar', &response)
         stub.post('/', &response)
         stub.get('/other', &response)
+        stub.get('/broken', &broken)
       end
     end
   end
@@ -58,6 +61,11 @@
     expect(post('/').body).to eq('request:3')
   end
 
+  it 'does not cache responses with invalid status code' do
+    expect(get('/broken').body).to eq('request:1')
+    expect(get('/broken').body).to eq('request:2')
+  end
+
   context ":ignore_params" do
     let(:options) { {:ignore_params => %w[ utm_source utm_term ]} }