From a7745b0c171e6d3dba194fdfefb772ce42d1233b Mon Sep 17 00:00:00 2001
From: stephann <3025661+stephannv@users.noreply.github.com>
Date: Thu, 11 Jan 2024 08:30:30 -0300
Subject: [PATCH] feat: Raise error on state constant name conflict

---
 lib/statesman/exceptions.rb       |  2 ++
 lib/statesman/machine.rb          |  2 +-
 spec/statesman/exceptions_spec.rb | 10 ++++++++++
 spec/statesman/machine_spec.rb    |  5 +++--
 4 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/lib/statesman/exceptions.rb b/lib/statesman/exceptions.rb
index 96adcc51..a870ac2a 100644
--- a/lib/statesman/exceptions.rb
+++ b/lib/statesman/exceptions.rb
@@ -11,6 +11,8 @@ class TransitionConflictError < StandardError; end
 
   class MissingTransitionAssociation < StandardError; end
 
+  class StateConstantConflictError < StandardError; end
+
   class TransitionFailedError < StandardError
     def initialize(from, to)
       @from = from
diff --git a/lib/statesman/machine.rb b/lib/statesman/machine.rb
index bde86f22..26e60b5e 100644
--- a/lib/statesman/machine.rb
+++ b/lib/statesman/machine.rb
@@ -169,7 +169,7 @@ def define_state_constant(state_name)
         constant_name = state_name.upcase
 
         if const_defined?(constant_name)
-          warn "Name conflict: '#{self.class.name}::#{constant_name}' is already defined"
+          raise StateConstantConflictError, "Name conflict: '#{self.class.name}::#{constant_name}' is already defined"
         else
           const_set(constant_name, state_name)
         end
diff --git a/spec/statesman/exceptions_spec.rb b/spec/statesman/exceptions_spec.rb
index 36e0b7d9..bd7ccc4e 100644
--- a/spec/statesman/exceptions_spec.rb
+++ b/spec/statesman/exceptions_spec.rb
@@ -51,6 +51,16 @@
     end
   end
 
+  describe "StateConstantConflictError" do
+    subject(:error) { Statesman::StateConstantConflictError.new }
+
+    its(:message) { is_expected.to eq("Statesman::StateConstantConflictError") }
+
+    its "string matches its message" do
+      expect(error.to_s).to eq(error.message)
+    end
+  end
+
   describe "TransitionFailedError" do
     subject(:error) { Statesman::TransitionFailedError.new("from", "to") }
 
diff --git a/spec/statesman/machine_spec.rb b/spec/statesman/machine_spec.rb
index 6a3da4e7..b8609c1e 100644
--- a/spec/statesman/machine_spec.rb
+++ b/spec/statesman/machine_spec.rb
@@ -31,9 +31,10 @@
     context "when state name constant is already defined" do
       it "warns about name conflict" do
         machine.const_set(:SOME_CONST, "some const")
-        warning_message = "Name conflict: 'Class::SOME_CONST' is already defined\n"
 
-        expect { machine.state(:some_const) }.to output(warning_message).to_stderr
+        expect { machine.state(:some_const) }.to raise_error(
+          Statesman::StateConstantConflictError, "Name conflict: 'Class::SOME_CONST' is already defined"
+        )
       end
     end
   end