2 files changed, 44 insertions, 8 deletions
diff --git a/spec/ruby/core/exception/detailed_message_spec.rb b/spec/ruby/core/exception/detailed_message_spec.rb
index bd85927dbe..fbe4443daa 100644
--- a/spec/ruby/core/exception/detailed_message_spec.rb
+++ b/spec/ruby/core/exception/detailed_message_spec.rb
@@ -7,6 +7,14 @@ describe "Exception#detailed_message" do
       RuntimeError.new("new error").detailed_message.should == "new error (RuntimeError)"
     end
 
+    it "is called by #full_message to allow message customization" do
+      exception = Exception.new("new error")
+      def exception.detailed_message(**)
+        "<prefix>#{message}<suffix>"
+      end
+      exception.full_message(highlight: false).should.include? "<prefix>new error<suffix>"
+    end
+
     it "accepts highlight keyword argument and adds escape control sequences" do
       RuntimeError.new("new error").detailed_message(highlight: true).should == "\e[1mnew error (\e[1;4mRuntimeError\e[m\e[1m)\e[m"
     end
@@ -23,13 +31,13 @@ describe "Exception#detailed_message" do
       RuntimeError.new("").detailed_message.should == "unhandled exception"
     end
 
-    it "returns just class name for an instance of RuntimeError sublass with empty message" do
+    it "returns just class name for an instance of RuntimeError subclass with empty message" do
       DetailedMessageSpec::C.new("").detailed_message.should == "DetailedMessageSpec::C"
     end
 
     it "returns a generated class name for an instance of RuntimeError anonymous subclass with empty message" do
       klass = Class.new(RuntimeError)
-      klass.new("").detailed_message.should =~  /\A#<Class:0x\h+>\z/
+      klass.new("").detailed_message.should =~ /\A#<Class:0x\h+>\z/
     end
   end
 end
diff --git a/spec/ruby/core/exception/full_message_spec.rb b/spec/ruby/core/exception/full_message_spec.rb
index ee66582022..e15649ca75 100644
--- a/spec/ruby/core/exception/full_message_spec.rb
+++ b/spec/ruby/core/exception/full_message_spec.rb
@@ -107,21 +107,49 @@ describe "Exception#full_message" do
   ruby_version_is "3.2" do
     it "relies on #detailed_message" do
       e = RuntimeError.new("new error")
-      e.define_singleton_method(:detailed_message) { |**opt| "DETAILED MESSAGE" }
+      e.define_singleton_method(:detailed_message) { |**| "DETAILED MESSAGE" }
 
       e.full_message.lines.first.should =~ /DETAILED MESSAGE/
     end
 
-    it "passes all its own keyword arguments to #detailed_message" do
+    it "passes all its own keyword arguments (with :highlight default value and without :order default value) to #detailed_message" do
       e = RuntimeError.new("new error")
-      opt_ = nil
-      e.define_singleton_method(:detailed_message) do |**opt|
-        opt_ = opt
+      options_passed = nil
+      e.define_singleton_method(:detailed_message) do |**options|
+        options_passed = options
         "DETAILED MESSAGE"
       end
 
       e.full_message(foo: "bar")
-      opt_.should == { foo: "bar", highlight: Exception.to_tty? }
+      options_passed.should == { foo: "bar", highlight: Exception.to_tty? }
+    end
+
+    it "converts #detailed_message returned value to String if it isn't a String" do
+      message = Object.new
+      def message.to_str; "DETAILED MESSAGE"; end
+
+      e = RuntimeError.new("new error")
+      e.define_singleton_method(:detailed_message) { |**| message }
+
+      e.full_message.lines.first.should =~ /DETAILED MESSAGE/
+    end
+
+    it "uses class name if #detailed_message returns nil" do
+      e = RuntimeError.new("new error")
+      e.define_singleton_method(:detailed_message) { |**| nil }
+
+      e.full_message(highlight: false).lines.first.should =~ /RuntimeError/
+      e.full_message(highlight: true).lines.first.should =~ /#{Regexp.escape("\e[1;4mRuntimeError\e[m")}/
+    end
+
+    it "uses class name if exception object doesn't respond to #detailed_message" do
+      e = RuntimeError.new("new error")
+      class << e
+        undef :detailed_message
+      end
+
+      e.full_message(highlight: false).lines.first.should =~ /RuntimeError/
+      e.full_message(highlight: true).lines.first.should =~ /#{Regexp.escape("\e[1;4mRuntimeError\e[m")}/
     end
   end
 end