Properly populate and invalidate local_cache in cas and cas_multi

lib/active_support/cache/memcached_store.rb

@@ -80,17 +80,27 @@ def read_multi(*names)
       def cas(name, options = nil)
         options = merged_options(options)
         key = normalize_key(name, options)
+        payload = nil
 
-        handle_exceptions(return_value_on_error: false) do
+        success = handle_exceptions(return_value_on_error: false) do
           instrument(:cas, name, options) do
             @connection.cas(key, expiration(options)) do |raw_value|
               entry = deserialize_entry(raw_value)
               value = yield entry.value
-              serialize_entry(Entry.new(value, **options), **options)
+              payload = serialize_entry(Entry.new(value, **options), **options)
             end
           end
-          true
         end
+
+        success = success != false # can return nil on success
+
+        if success
+          local_cache.write_entry(key, payload) if local_cache
+        else
+          local_cache.delete_entry(key) if local_cache
+        end
+
+        success
       end
 
       def cas_multi(*names, **options)
@@ -101,7 +111,7 @@ def cas_multi(*names, **options)
 
         handle_exceptions(return_value_on_error: false) do
           instrument(:cas_multi, names, options) do
-            @connection.cas(keys_to_names.keys, expiration(options)) do |raw_values|
+            written_payloads = @connection.cas(keys_to_names.keys, expiration(options)) do |raw_values|
               values = {}
 
               raw_values.each do |key, raw_value|
@@ -117,6 +127,17 @@ def cas_multi(*names, **options)
 
               Hash[serialized_values]
             end
+
+            if local_cache
+              keys_to_names.each_key do |key|
+                if written_payloads.key?(key)
+                  local_cache.write_entry(key, written_payloads[key])
+                else
+                  local_cache.delete_entry(key)
+                end
+              end
+            end
+
             true
           end
         end

test/test_memcached_store.rb

@@ -80,6 +80,18 @@ def test_cas
     assert_equal 'bar', @cache.read('foo')
   end
 
+  def test_cas_local_cache
+    @cache.with_local_cache do
+      @cache.write('foo', 'plop')
+      assert(@cache.cas('foo') do |value|
+        assert_equal 'plop', value
+        'bar'
+      end)
+      assert_equal 'bar', @cache.read('foo')
+      assert_equal 'bar', @peek.read('foo')
+    end
+  end
+
   def test_cas_with_cache_miss
     refute @cache.cas('not_exist') { |_value| flunk }
   end
@@ -93,6 +105,17 @@ def test_cas_with_conflict
     assert_equal 'baz', @cache.read('foo')
   end
 
+  def test_cas_local_cache_with_conflict
+    @cache.with_local_cache do
+      @cache.write('foo', 'bar')
+      refute @cache.cas('foo') { |_value|
+        @peek.write('foo', 'baz')
+        'biz'
+      }
+      assert_equal 'baz', @cache.read('foo')
+    end
+  end
+
   def test_cas_multi_with_empty_set
     refute @cache.cas_multi { |_hash| flunk }
   end
@@ -107,6 +130,19 @@ def test_cas_multi
     assert_equal({ "foo" => "baz", "fud" => "buz" }, @cache.read_multi('foo', 'fud'))
   end
 
+  def test_cas_multi_with_local_cache
+    @cache.with_local_cache do
+      @cache.write('foo', 'bar')
+      @cache.write('fud', 'biz')
+      assert_equal true, (@cache.cas_multi('foo', 'fud') do |hash|
+        assert_equal({ "foo" => "bar", "fud" => "biz" }, hash)
+        @peek.write('fud', 'blam')
+        { "foo" => "baz", "fud" => "buz" }
+      end)
+      assert_equal({ "foo" => "baz", "fud" => "blam" }, @cache.read_multi('foo', 'fud'))
+    end
+  end
+
   def test_cas_multi_with_altered_key
     @cache.write('foo', 'baz')
     assert @cache.cas_multi('foo') { |_hash| { 'fu' => 'baz' } }