[ISSUE-62]: Avoid cache nil or empty array responses (#63)

* Refactor `find_via_reload(key, *arguments)`

    - To avoid cache `nil` or `[]` responses/objects
    - Also refactor rspecs

* Add consecuent request on rspec

    - To check that after non cached `nil` or `[]` response we are
      caching valid vulues.

* Revert last commit

lib/cached_resource/caching.rb

@@ -40,7 +40,7 @@ def find_via_cache(key, *arguments)
       # Re/send the request to fetch the resource
       def find_via_reload(key, *arguments)
         object = find_without_cache(*arguments)
-        return object unless cached_resource.enabled
+        return object unless should_cache?(object)
 
         cache_collection_synchronize(object, *arguments) if cached_resource.collection_synchronize
         return object if !cached_resource.cache_collections && is_any_collection?(*arguments)
@@ -79,6 +79,12 @@ def update_collection_cache(updates, *arguments)
         end
       end
 
+      # Avoid cache nil or [] objects
+      def should_cache?(object)
+        return false unless cached_resource.enabled
+        object.respond_to?(:empty?) ? !object.empty? : !!object
+      end
+
       # Determine if the given arguments represent
       # the entire collection of objects.
       def is_collection?(*arguments)

spec/cached_resource/caching_spec.rb

@@ -33,6 +33,7 @@ class NotTheThing < ActiveResource::Base
     @other_string_thing_json = @other_string_thing.to_json
     @date_thing_json = @date_thing.to_json
     @nil_thing = nil.to_json
+    @empty_array_thing = [].to_json
     @not_the_thing = {:not_the_thing => {:id => 1, :name => "Not"}}
     @not_the_thing_json = @not_the_thing.to_json
   end
@@ -59,22 +60,27 @@ class NotTheThing < ActiveResource::Base
         mock.get "/things/1.json?foo=bar", {}, @thing_json
         mock.get "/things/fded.json", {}, @string_thing_json
         mock.get "/things.json?name=42", {}, @nil_thing, 404
+        mock.get "/things.json?name=43", {}, @empty_array_thing
         mock.get "/things/4.json", {}, @date_thing_json
         mock.get "/not_the_things/1.json", {}, @not_the_thing_json
       end
     end
 
     it "should cache a response" do
       result = Thing.find(1)
-
       read_from_cache("thing/1").should == result
     end
 
-    it "should cache a nil response" do
-      result = Thing.find(:all, :params => { :name => '42' })
+    it "shouldn't cache nil response" do
+      Thing.find(:all, :params => { :name => '42' })
       read_from_cache("thing/all/name/42").should == nil
     end
 
+    it "shouldn't cache [] response" do
+      Thing.find(:all, :params => { :name => '43' })
+      read_from_cache("thing/all/name/43").should == nil
+    end
+
     it "should cache a response for a string primary key" do
       result = Thing.find("fded")
       read_from_cache("thing/fded").should == result