Avoid mutation of @DaTa from external reference

Added a ternany and .dup to the return of 'with_thing_at' to avoid
return a mutable reference that allowed in memory mutation of the
@DaTa struct inside MockRedis

This commit done on the dime of:
Simply Measured
twitter: @SimplyMeasured
web: http://www.simplymeasured.com

Change-Id: I7ea498929a9183f83f40b6f4e6589b7aaacd397b
Reviewed-on: https://gerrit.causes.com/19655
Reviewed-by: Aiden Scandella <aiden@causes.com>
Tested-by: jenkins <jenkins@causes.com>

CHANGELOG.md

@@ -1,3 +1,6 @@
+### 0.6.6 (unreleased)
+* Avoid mutation of @data from external reference
+
 ### 0.6.5
 * Fix `zrevrange` to return an empty array on invalid range
 * Fix `srandmember` spec on redis-rb 3.0.3

lib/mock_redis/utility_methods.rb

@@ -9,12 +9,16 @@ def with_thing_at(key, assertion, empty_thing_generator)
         data_key_ref = data[key]
         ret = yield data[key]
         data[key] = data_key_ref if data[key].nil?
-        ret
+        primitive?(ret) ? ret.dup : ret
       ensure
         clean_up_empties_at(key)
       end
     end
 
+    def primitive?(value)
+      value.kind_of?(::Array) || value.kind_of?(::Hash) || value.kind_of?(::String)
+    end
+
     def clean_up_empties_at(key)
       if data[key] && data[key].empty?
         del(key)

spec/commands/hgetall_spec.rb

@@ -18,5 +18,15 @@
     @redises.hgetall('mock-redis-test:nonesuch').should == {}
   end
 
+  it "doesn't return a mutable reference to the returned data" do
+    mr = MockRedis.new
+    mr.hset(@key, 'k1', 'v1')
+    mr.hset(@key, 'k2', 'v2')
+    hash =  mr.hgetall(@key)
+    hash['dont'] = 'mutate'
+    new_hash = mr.hgetall(@key)
+    new_hash.keys.sort.should == ['k1', 'k2']
+  end
+
   it_should_behave_like "a hash-only command"
 end