MONGOID-5422 - Configuration DSL should not require an argument to its block (Rails parity)

docs/release-notes/mongoid-8.0.txt

@@ -315,6 +315,31 @@ Mongoid 7 behavior:
   end
 
 
+Configuration DSL No Longer Requires an Argument to its Block
+-------------------------------------------------------------
+
+In Mongoid 8.0, it is now possible to use ``Mongoid.configure`` without
+providing an argument to its block:
+
+.. code-block:: ruby
+
+  Mongoid.configure do
+    connect_to("mongoid_test")
+
+    # Use config method when assigning variables
+    config.preload_models = true
+
+Note that ``configure`` will continue to support a block argument.
+The following is equivalent to the above:
+
+.. code-block:: ruby
+
+  Mongoid.configure do |config|
+    config.connect_to("mongoid_test")
+
+    config.preload_models = true
+
+
 ``#pluck`` on Embedded Criteria Returns ``nil`` Values
 ------------------------------------------------------
 

lib/mongoid.rb

@@ -57,9 +57,19 @@ module Mongoid
   #     }
   #   end
   #
+  # @example Using a block without an argument. Use `config` inside
+  #   the block to perform variable assignment.
+  #
+  #   Mongoid.configure do
+  #     connect_to("mongoid_test")
+  #
+  #     config.preload_models = true
+  #
   # @return [ Config ] The configuration object.
-  def configure
-    block_given? ? yield(Config) : Config
+  def configure(&block)
+    return Config unless block_given?
+
+    block.arity == 0 ? Config.instance_exec(&block) : yield(Config)
   end
 
   # Convenience method for getting the default client.

lib/mongoid/config.rb

@@ -125,6 +125,13 @@ module Config
     # always return a Hash.
     option :legacy_attributes, default: false
 
+    # Returns the Config singleton, for use in the configure DSL.
+    #
+    # @return [ self ] The Config singleton.
+    def config
+      self
+    end
+
     # Has Mongoid been configured? This is checking that at least a valid
     # client config exists.
     #

spec/mongoid_spec.rb

@@ -13,22 +13,51 @@
       end
     end
 
-    context "when a block is supplied" do
+    context "when a block is given" do
 
-      before do
+      after do
         Mongoid.configure do |config|
-          config.preload_models = true
+          config.preload_models = false
         end
       end
 
-      after do
-        Mongoid.configure do |config|
-          config.preload_models = false
+      context "with arity 0" do
+
+        before do
+          Mongoid.configure do
+            config.preload_models = true
+          end
+        end
+
+        it "sets the values on the config instance" do
+          expect(Mongoid.preload_models).to be true
+        end
+      end
+
+      context "with arity 1" do
+
+        before do
+          Mongoid.configure do |config|
+            config.preload_models = true
+          end
+        end
+
+        it "sets the values on the config instance" do
+          expect(Mongoid.preload_models).to be true
         end
       end
 
-      it "sets the values on the config instance" do
-        expect(Mongoid.preload_models).to be true
+      context "with arity 2" do
+
+        before do
+          Mongoid.configure do |config, _other|
+            config.preload_models = true
+          end
+        end
+
+        it "sets the values on the config instance" do
+          expect(Mongoid.preload_models).to be true
+        end
       end
     end
   end