Make Container hooks more useful for dynamic registration

lib/dry/system/container.rb

@@ -329,8 +329,8 @@ def finalize!(freeze: true, &block)
 
           @__finalized__ = true
 
-          self.freeze if freeze
           hooks[:after_finalize].each { |hook| instance_eval(&hook) }
+          self.freeze if freeze
           self
         end
 
@@ -486,6 +486,15 @@ def root
           config.root
         end
 
+        # @api public
+        def register(key, *)
+          super
+
+          hooks[:after_register].each { |hook| instance_exec(key, &hook) }
+
+          self
+        end
+
         # @api public
         def resolve(key)
           load_component(key) unless finalized?

spec/unit/container/hooks/after_hooks_spec.rb

@@ -0,0 +1,44 @@
+# frozen_string_literal: true
+
+RSpec.describe Dry::System::Container do
+  subject(:system) do
+    Class.new(described_class)
+  end
+
+  describe "after_register hook" do
+    it "executes after a new key is registered" do
+      expect { |hook|
+        system.after(:register, &hook)
+        system.register(:foo) { "bar" }
+      }.to yield_with_args(:foo)
+    end
+
+    it "provides the fully-qualified key" do
+      expect { |hook|
+        system.after(:register, &hook)
+        system.namespace :foo do
+          register(:bar) { "baz" }
+        end
+      }.to yield_with_args("foo.bar")
+    end
+  end
+
+  describe "after_finalize hook" do
+    it "executes after finalization" do
+      expect { |hook|
+        system.after(:finalize, &hook)
+        system.finalize!
+      }.to yield_control
+    end
+
+    it "executes before the container is frozen" do
+      is_frozen = nil
+
+      system.after(:finalize) { is_frozen = frozen? }
+      system.finalize!
+
+      expect(is_frozen).to eq false
+      expect(system).to be_frozen
+    end
+  end
+end