Allow custom ordering by name on the cli

Author: JonRowe

features/command_line/order.feature

@@ -69,6 +69,32 @@ Scenario: Order can be psuedo randomised (seed used here to fix the ordering for
         does something
       """
 
+Scenario: Configure custom ordering
+  Given a file named "example_spec.rb" with:
+    """ruby
+    RSpec.configure do |config|
+      config.register_ordering(:reverse) do |examples|
+        examples.reverse
+      end
+      config.order = :reverse
+    end
+
+    RSpec.describe "something", order: :reverse do
+      it "does something" do
+      end
+
+      it "in order" do
+      end
+    end
+    """
+    When I run `rspec example_spec.rb --format documentation --order reverse`
+    Then the output should contain:
+      """
+      something
+        in order
+        does something
+      """
+
 Scenario: Override order to `defined` when another order is set
   Given a file named "example_spec.rb" with:
     """ruby

lib/rspec/core/ordering.rb

@@ -171,9 +171,20 @@ def order=(type)
                             :defined
                           elsif order == 'recently-modified'
                             :recently_modified
+                          else
+                            order.to_sym
                           end
 
-          register_ordering(:global, ordering_registry.fetch(ordering_name)) if ordering_name
+          if ordering_name
+            strategy =
+              if ordering_registry.has_strategy?(ordering_name)
+                ordering_registry.fetch(ordering_name)
+              else
+                Delayed.new(ordering_registry, ordering_name)
+              end
+
+            register_ordering(:global, strategy)
+          end
         end
 
         def force(hash)

spec/rspec/core/configuration_spec.rb

@@ -2602,6 +2602,49 @@ def use_seed_on(registry)
           expect(ordering_strategy.order(list)).to eq([1, 2, 3, 4])
         end
       end
+
+      context 'given a custom ordering strategy' do
+        before do
+          allow(RSpec).to receive_messages(:configuration => config)
+        end
+
+        it 'will lookup a previously registed ordering strategy' do
+          config.register_ordering(:custom_scheme) { |list| list.reverse }
+
+          config.order = :custom_scheme
+
+          strategy = config.ordering_registry.fetch(:global)
+          expect(strategy.order([1, 2, 3, 4])).to eq [4, 3, 2, 1]
+        end
+
+        it 'will defer lookup until running' do
+          config.order = :custom_scheme
+
+          strategy = config.ordering_registry.fetch(:global)
+          expect(strategy).to be_an_instance_of(Ordering::Delayed)
+
+          config.register_ordering(:custom_scheme) { |list| list.reverse }
+          expect(strategy.order([1, 2, 3, 4])).to eq [4, 3, 2, 1]
+        end
+
+        it 'will raise an error if ordering is not present when needed' do
+          config.order = :custom_scheme
+
+          strategy = config.ordering_registry.fetch(:global)
+          expect(strategy).to be_an_instance_of(Ordering::Delayed)
+
+          expect { strategy.order([1, 2, 3, 4]) }.to raise_error("Undefined ordering strategy :custom_scheme")
+        end
+
+        it 'will lookup schemes as symbols even if given as strings' do
+          config.order = 'custom_scheme'
+
+          config.register_ordering(:custom_scheme) { |list| list.reverse }
+
+          strategy = config.ordering_registry.fetch(:global)
+          expect(strategy.order([1, 2, 3, 4])).to eq [4, 3, 2, 1]
+        end
+      end
     end
 
     describe "#register_ordering" do