[GR-19220] Fix Struct#inspect in anonymous classes/modules (#2870)

PullRequest: truffleruby/3655

Author: eregon

CHANGELOG.md

@@ -79,6 +79,7 @@ Compatibility:
 * `Kernel#exit!`, killing Fibers and internal errors do not run code in `ensure` clauses anymore, the same as CRuby (@eregon).
 * Implement `UnboundMethod#original_name` (@paracycle, @nirvdrum).
 * Implement `Thread#native_thread_id` method (#2733, @horakivo).
+* Modify `Struct#{inspect,to_s}` to match MRI when the struct is nested inside of an anonymous class or module (@st0012, @nirvdrum).
 
 Performance:
 

spec/ruby/core/struct/inspect_spec.rb

@@ -3,10 +3,5 @@
 require_relative 'shared/inspect'
 
 describe "Struct#inspect" do
-  it "returns a string representation showing members and values" do
-    car = StructClasses::Car.new('Ford', 'Ranger')
-    car.inspect.should == '#<struct StructClasses::Car make="Ford", model="Ranger", year=nil>'
-  end
-
   it_behaves_like :struct_inspect, :inspect
 end

spec/ruby/core/struct/shared/inspect.rb

@@ -1,5 +1,28 @@
 describe :struct_inspect, shared: true do
+  it "returns a string representation showing members and values" do
+    car = StructClasses::Car.new('Ford', 'Ranger')
+    car.send(@method).should == '#<struct StructClasses::Car make="Ford", model="Ranger", year=nil>'
+  end
+
   it "returns a string representation without the class name for anonymous structs" do
     Struct.new(:a).new("").send(@method).should == '#<struct a="">'
   end
+
+  it "returns a string representation without the class name for structs nested in anonymous classes" do
+    c = Class.new
+    c.class_eval <<~DOC
+      class Foo < Struct.new(:a); end
+    DOC
+
+    c::Foo.new("").send(@method).should == '#<struct a="">'
+  end
+
+  it "returns a string representation without the class name for structs nested in anonymous modules" do
+    m = Module.new
+    m.module_eval <<~DOC
+      class Foo < Struct.new(:a); end
+    DOC
+
+    m::Foo.new("").send(@method).should == '#<struct a="">'
+  end
 end

src/main/ruby/truffleruby/core/struct.rb

@@ -147,7 +147,7 @@ def to_s
 
       name = self.class.name
 
-      if Primitive.nil?(name) || name.empty?
+      if Primitive.nil?(name) || name.empty? || name[0] == '#'
         return "#<struct #{values.join(', ')}>"
       else
         return "#<struct #{self.class.name} #{values.join(', ')}>"