Clear the cache for the key when set

If setting a cache value is called within a TX and then the value is
accessed, then the old value is retrieved from the cache.

The fix is to clear the cached value for the var name immediately after
calling save!. Note, it is still appropriate to clear cache values upon
commit due to race conditions.

lib/rails-settings/cached_settings.rb

@@ -24,6 +24,10 @@ def cache_key(var_name, scope_object)
         scope << "#{var_name}"
       end
 
+      def remove_cache_key(var_name, scope_object)
+        Rails.cache.delete(cache_key(var_name, scope_object))
+      end
+
       def [](var_name)
         value = Rails.cache.fetch(cache_key(var_name, @object)) do
           super(var_name)
@@ -36,6 +40,15 @@ def [](var_name)
         end
       end
 
+      # set a setting value by [] notation
+      def []=(var_name, value)
+        super
+
+        Rails.cache.write(cache_key(var_name, @object),value)
+
+        value
+      end
+
       def save_default(key, value)
         return false unless self[key].nil?
         self[key] = value

spec/rails-settings-cached/cached_setting_spec.rb

@@ -1,6 +1,7 @@
 require 'spec_helper'
 
 describe RailsSettings::CachedSettings do
+  before(:each) { Rails.cache.clear }
   describe '.cache_key' do
     it 'should work with instance method' do
       obj = Setting.unscoped.first
@@ -43,12 +44,27 @@
     queries_count = count_queries do
       expect(described_class["gender"]).to be nil
       described_class["gender"] = "female"
+
+      # Call 4 times, make sure value is cached by fact number of queries does not go up.
+      expect(described_class["gender"]).to eq("female")
+      expect(described_class["gender"]).to eq("female")
       expect(described_class["gender"]).to eq("female")
       expect(described_class["gender"]).to eq("female")
     end
     expect(queries_count).to eq(5)
   end
 
+  it "caches unscoped settings" do
+    expect(described_class["gender"]).to eq("female")
+    ActiveRecord::Base.transaction do
+      described_class["gender"] = "trans"
+      expect(described_class["gender"]).to eq("trans")
+    end
+
+    expect(described_class["gender"]).to eq("trans")
+  end
+
+
   it "caches scoped settings" do
     user = User.create!(login: 'another_test', password: 'foobar')
 
@@ -61,6 +77,25 @@
     expect(queries_count).to eq(6)
   end
 
+  it "caches scoped settings in transaction" do
+    user = User.create!(login: 'another_test2', password: 'foobar')
+
+    queries_count = count_queries do
+      expect(user.settings["gender"]).to be nil
+      ActiveRecord::Base.transaction do
+        user.settings["gender"] = "male"
+        expect(user.settings["gender"]).to eq("male")
+      end
+
+      # Call 4 times, make sure value is cached by fact number of queries does not go up.
+      expect(user.settings["gender"]).to eq("male")
+      expect(user.settings["gender"]).to eq("male")
+      expect(user.settings["gender"]).to eq("male")
+      expect(user.settings["gender"]).to eq("male")
+    end
+    expect(queries_count).to eq(6)
+  end
+
   it "caches values from db" do
     described_class["some_random_key"] = "asd"
     Rails.cache.clear