From e2fed5d464caa87e9d8a040feb1f17c621c1a18c Mon Sep 17 00:00:00 2001
From: Alexander Repnikov <aleksander.repnikov@gmail.com>
Date: Thu, 28 Dec 2023 16:53:24 +0100
Subject: [PATCH] Virtual & Pure methods macros raises an error if concrete
 method exists

---
 lib/virtual.rb                                    |  1 +
 lib/virtual/method_defined.rb                     | 15 +++++++++++++++
 lib/virtual/pure_method.rb                        |  5 +++++
 lib/virtual/virtual_method.rb                     |  5 +++++
 ...verrides_concrete.rb => overrides_concrete.rb} |  0
 ...verrides_concrete.rb => overrides_concrete.rb} |  0
 6 files changed, 26 insertions(+)
 create mode 100644 lib/virtual/method_defined.rb
 rename test/automated/pure_virtual/{_overrides_concrete.rb => overrides_concrete.rb} (100%)
 rename test/automated/virtual/{_overrides_concrete.rb => overrides_concrete.rb} (100%)

diff --git a/lib/virtual.rb b/lib/virtual.rb
index 03acce1..f82283f 100644
--- a/lib/virtual.rb
+++ b/lib/virtual.rb
@@ -1,3 +1,4 @@
+require 'virtual/method_defined'
 require 'virtual/virtual_method'
 require 'virtual/pure_method'
 require 'virtual/protocol_method'
diff --git a/lib/virtual/method_defined.rb b/lib/virtual/method_defined.rb
new file mode 100644
index 0000000..dcf5e52
--- /dev/null
+++ b/lib/virtual/method_defined.rb
@@ -0,0 +1,15 @@
+module Virtual
+  module MethodDefined
+    def self.call(target_class, method_name)
+      target_class.method_defined?(method_name, true) ||
+        target_class.private_method_defined?(method_name, true)
+    end
+
+    module SourceLocation
+      def self.get(target_class, method_name)
+        method = target_class.instance_method(method_name)
+        method.source_location.join(':')
+      end
+    end
+  end
+end
diff --git a/lib/virtual/pure_method.rb b/lib/virtual/pure_method.rb
index e710a0d..3ac1b46 100644
--- a/lib/virtual/pure_method.rb
+++ b/lib/virtual/pure_method.rb
@@ -3,6 +3,11 @@ module PureMethod
     Error = Class.new(RuntimeError)
 
     def self.define(target_class, method_name)
+      if MethodDefined.(target_class, method_name)
+        method_source_location = MethodDefined::SourceLocation.get(target_class, method_name)
+        raise Error, "Pure virtual (abstract) method #{method_name} of #{target_class.name} must not already be implemented (Source Location: #{method_source_location})"
+      end
+
       target_class.send(:define_method, method_name) do |*args|
         raise Error, "Pure virtual (abstract) method #{method_name} of #{self.class.name} must be implemented"
       end
diff --git a/lib/virtual/virtual_method.rb b/lib/virtual/virtual_method.rb
index 38c63de..e600278 100644
--- a/lib/virtual/virtual_method.rb
+++ b/lib/virtual/virtual_method.rb
@@ -6,6 +6,11 @@ def self.define(target_class, method_name, &blk)
       blk ||= proc do |*|
       end
 
+      if MethodDefined.(target_class, method_name)
+        method_source_location = MethodDefined::SourceLocation.get(target_class, method_name)
+        raise Error, "Virtual (abstract) method #{method_name} of #{target_class.name} must not already be implemented (Source Location: #{method_source_location})"
+      end
+
       target_class.send(:define_method, method_name, &blk)
     end
   end
diff --git a/test/automated/pure_virtual/_overrides_concrete.rb b/test/automated/pure_virtual/overrides_concrete.rb
similarity index 100%
rename from test/automated/pure_virtual/_overrides_concrete.rb
rename to test/automated/pure_virtual/overrides_concrete.rb
diff --git a/test/automated/virtual/_overrides_concrete.rb b/test/automated/virtual/overrides_concrete.rb
similarity index 100%
rename from test/automated/virtual/_overrides_concrete.rb
rename to test/automated/virtual/overrides_concrete.rb