Fix forced cache miss for fetch.

- Raised an argument error if no block is passed to #fetch with
'force: true' option is set.
- Added tests for the same.

activesupport/CHANGELOG.md

+*   Raise an argument error if no block is passed to #fetch with option
+    `force: true` is set.
+
+        cache.fetch('today', force: true) # => ArgumentError: Missing block
+
+    *Santosh Wadghule*
+
 *   `ActiveSupport::Duration` supports weeks and hours.
 
         [1.hour.inspect, 1.hour.value, 1.hour.parts]

activesupport/lib/active_support/cache.rb

@@ -198,10 +198,16 @@ def mute
       #   cache.fetch('city')   # => "Duckburgh"
       #
       # You may also specify additional options via the +options+ argument.
-      # Setting <tt>force: true</tt> will force a cache miss:
+      # Setting <tt>force: true</tt> will force a cache miss and return value of
+      # the block will be written to the cache under the given cache key.
       #
       #   cache.write('today', 'Monday')
-      #   cache.fetch('today', force: true)  # => nil
+      #   cache.fetch('today', force: true) { 'Tuesday' } # => 'Tuesday'
+      #
+      # It will raise an argument error if no block is passed to #fetch with
+      # option <tt>force: true</tt> is set.
+      #
+      #   cache.fetch('today', force: true) # => ArgumentError: Missing block
       #
       # Setting <tt>:compress</tt> will store a large cache entry set by the call
       # in a compressed format.
@@ -292,6 +298,8 @@ def fetch(name, options = nil)
           else
             save_block_result_to_cache(name, options) { |_name| yield _name }
           end
+        elsif options && options[:force]
+          raise ArgumentError, 'Missing block'
         else
           read(name, options)
         end

activesupport/test/caching_test.rb

@@ -266,6 +266,20 @@ def test_fetch_with_cached_nil
     end
   end
 
+  def test_fetch_with_forced_cache_miss_with_block
+    @cache.write('foo', 'bar')
+    assert_equal 'foo_bar', @cache.fetch('foo', force: true) { 'foo_bar' }
+  end
+
+  def test_fetch_with_forced_cache_miss_without_block
+    @cache.write('foo', 'bar')
+    assert_raises(ArgumentError, 'Missing block') do
+      @cache.fetch('foo', force: true)
+    end
+
+    assert_equal 'bar', @cache.read('foo')
+  end
+
   def test_should_read_and_write_hash
     assert @cache.write('foo', {:a => "b"})
     assert_equal({:a => "b"}, @cache.read('foo'))