From 9d0866c7d7b9cbe36a851744a37806e747e0e7a8 Mon Sep 17 00:00:00 2001
From: Jean Boussier <jean.boussier@gmail.com>
Date: Thu, 26 Sep 2019 10:41:43 +0200
Subject: [PATCH] [EXPERIMENTAL] Make Module#name return a frozen String

    * Always the same frozen String for a given Module or Class.
    * Avoids extra allocations whenever calling Module#name.
    * See [Feature #16150]
---
 NEWS                               |  4 ++++
 spec/ruby/core/module/name_spec.rb | 24 +++++++++++++++++++-----
 variable.c                         |  5 +----
 3 files changed, 24 insertions(+), 9 deletions(-)

diff --git a/NEWS b/NEWS
index 4e168518ca..d23cadde3e 100644
--- a/NEWS
+++ b/NEWS
@@ -174,6 +174,10 @@ Module::
 
     * Module#autoload? now takes an +inherit+ optional argument, like as
       Module#const_defined?.  [Feature #15777]
+    
+    * Module#name now always return a frozen String. The returned String is
+      always the same for a given Module. This change is experimental
+      [Feature #16150]
 
 ObjectSpace::WeakMap::
 
diff --git a/spec/ruby/core/module/name_spec.rb b/spec/ruby/core/module/name_spec.rb
index d64684319c..36a91f5be5 100644
--- a/spec/ruby/core/module/name_spec.rb
+++ b/spec/ruby/core/module/name_spec.rb
@@ -102,13 +102,27 @@ describe "Module#name" do
     m::N.name.should == "ModuleSpecs::Anonymous::E::N"
   end
 
-  it "returns a mutable string" do
-    ModuleSpecs.name.frozen?.should be_false
+  ruby_version_is ""..."2.7" do
+    it "returns a mutable string" do
+      ModuleSpecs.name.frozen?.should be_false
+    end
+
+    it "returns a mutable string that when mutated does not modify the original module name" do
+      ModuleSpecs.name << "foo"
+
+      ModuleSpecs.name.should == "ModuleSpecs"
+    end
   end
 
-  it "returns a mutable string that when mutated does not modify the original module name" do
-    ModuleSpecs.name << "foo"
+  ruby_version_is "2.7" do
+    it "returns a frozen String" do
+      ModuleSpecs.name.frozen?.should == true
+    end
 
-    ModuleSpecs.name.should == "ModuleSpecs"
+    it "always returns the same String for a given Module" do
+      s1 = ModuleSpecs.name
+      s2 = ModuleSpecs.name
+      s1.should equal(s2)
+    end
   end
 end
diff --git a/variable.c b/variable.c
index 9fd075c21c..aafb6f4725 100644
--- a/variable.c
+++ b/variable.c
@@ -107,10 +107,7 @@ VALUE
 rb_mod_name(VALUE mod)
 {
     int permanent;
-    VALUE path = classname(mod, &permanent);
-
-    if (!NIL_P(path)) return rb_str_dup(path);
-    return path;
+    return classname(mod, &permanent);
 }
 
 static VALUE