Implement deep merge for environment configuration

dot-net/Centroid.Tests/ConfigTest.cs

@@ -142,7 +142,7 @@ public void test_enumerating_json_object()
             }
             Assert.That(itemCount, Is.EqualTo(1));
         }
-
+            
         [Test]
         public void test_all_environment_is_not_case_sensitive()
         {
@@ -154,5 +154,27 @@ public void test_all_environment_is_not_case_sensitive()
             var lowerCaseAllEnvironmentConfig = lowerCaseAllConfig.ForEnvironment("Prod");
             Assert.That(lowerCaseAllEnvironmentConfig.AllOnly, Is.EqualTo("works"));
         }
+
+        [Test]
+        public void supports_deep_merge()
+        {
+            const string json = @"
+                {
+                    ""Dev"": {
+                        ""Database"": {
+                            ""Server"": ""the-dev-database""
+                        }
+                    },
+                    ""All"": {
+                        ""Database"": {
+                            ""MigrationsPath"": ""path/to/migrations""
+                        }
+                    }
+                }";
+
+            dynamic config = new Config(json).ForEnvironment("Dev");
+            Assert.That(config.Database.Server, Is.EqualTo("the-dev-database"));
+            Assert.That(config.Database.MigrationsPath, Is.EqualTo("path/to/migrations"));
+        }
     }
-}
+}

dot-net/Centroid/Config.cs

@@ -45,10 +45,8 @@ public dynamic ForEnvironment(string environment)
                 return new Config(envConfig);
             }
 
-            foreach (var cfg in envConfig)
-            {
-                allConfig[cfg.Name] = cfg.Value;
-            }
+            MergeInto(allConfig, envConfig);
+
             return new Config(allConfig);
         }
 
@@ -148,5 +146,33 @@ void ValidateUniqueKeys()
             var keys = duplicates.SelectMany(d => d.Select(x => x.Key));
             throw new InvalidOperationException("Centroid.Config instance contains duplicate keys: " + string.Join(", ", keys));
         }
+
+        static void MergeInto(JContainer left, JToken right)
+        {
+            foreach (var rightChild in right.Children<JProperty>())
+            {
+                var rightChildProperty = rightChild;
+                var leftProperty = left.SelectToken(rightChildProperty.Name);
+
+                if (leftProperty == null)
+                {
+                    left.Add(rightChild);
+                }
+                else
+                {
+                    var leftObject = leftProperty as JObject;
+
+                    if (leftObject == null)
+                    {
+                        var leftParent = (JProperty) leftProperty.Parent;
+                        leftParent.Value = rightChildProperty.Value;
+                    }
+                    else
+                    {
+                        MergeInto(leftObject, rightChildProperty.Value);
+                    }
+                }
+            }
+        }
     }
 }

python/centroid.py

@@ -47,9 +47,8 @@ def for_environment(self, env):
             return Config(env_json)
 
         all_json = _get_value(actual_key, self.raw_config)
-        all_json.update(env_json);
 
-        return Config(all_json)
+        return Config(_dict_merge(all_json, env_json))
 
     @staticmethod
     def from_file(filename):
@@ -75,3 +74,13 @@ def _get_actual_key(key, hashtable):
     if len(result) > 0:
         return result[0]
     return None
+
+def _dict_merge(left, right):
+    if not isinstance(right, dict):
+        return right
+    for k, v in right.iteritems():
+        if k in left and isinstance(left[k], dict):
+            left[k] = _dict_merge(left[k], v)
+        else:
+            left[k] = v
+    return left

python/tests.py

@@ -97,3 +97,9 @@ def test_all_environment_is_not_case_sensitive(self):
         config = Config('{"Prod": {"Shared": "production!"}, "all": {"Shared": "none", "AllOnly": "works"}}')
         config = config.for_environment("Prod")
         self.assertEqual(config.all_only, "works")
+
+    def test_supports_deep_merge(self):
+        config = Config('{"Prod": {"Database": {"Server": "prod-sql"}}, "All": {"Database": {"MigrationsPath": "path/to/migrations"}}}')
+        config = config.for_environment("Prod")
+        self.assertEqual(config.database.server, "prod-sql")
+        self.assertEqual(config.database.migrations_path, "path/to/migrations")

ruby/lib/centroid.rb

@@ -40,7 +40,7 @@ def for_environment(env)
         Config.new(env_json)
       else
         all_json = raw_config[all_key]
-        Config.new(all_json.merge(env_json))
+        Config.new(deep_merge(all_json, env_json))
       end
     end
 
@@ -72,5 +72,20 @@ def validate_unique_keys!
       keys = dups.values.flat_map { |d| d.map { |e| e[:key] } }
       raise KeyError, "Centroid::Config instance contains duplicate keys: #{keys.join(', ')}"
     end
+
+    def deep_merge(left, right)
+      return right if not right.is_a?(Hash)
+
+      right.each_pair do |k, rv|
+        lv = left[k]
+        left[k] = if lv.is_a?(Hash) && rv.is_a?(Hash)
+          deep_merge(lv, rv)
+        else
+          rv
+        end
+      end
+
+      left
+    end
   end
 end

ruby/test/centroid_test.rb

@@ -94,4 +94,11 @@ def test_all_environment_is_not_case_sensitive
     config = config.for_environment("Prod")
     assert_equal(config.all_only, "works")
   end
+
+  def test_supports_deep_merge
+    config = Centroid::Config.new('{"Prod": {"Database": {"Server": "prod-sql"}}, "All": {"Database": {"MigrationsPath": "path/to/migrations"}}}')
+    config = config.for_environment("Prod")
+    assert_equal(config.database.server, "prod-sql")
+    assert_equal(config.database.migrations_path, "path/to/migrations")
+  end
 end