From 65c0a38cb6c5b357bdf60f9e977f317cea707b93 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?David=20Rodr=C3=ADguez?= <deivid.rodriguez@riseup.net>
Date: Thu, 1 Oct 2020 14:42:41 +0200
Subject: [PATCH 1/2] Small refactor in `warn` monkeypatch

Only need to set `kw[:uplevel]` when not already set.
---
 lib/rubygems/core_ext/kernel_warn.rb | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/lib/rubygems/core_ext/kernel_warn.rb b/lib/rubygems/core_ext/kernel_warn.rb
index e030ef815c9d..3ed16c8cc7ed 100644
--- a/lib/rubygems/core_ext/kernel_warn.rb
+++ b/lib/rubygems/core_ext/kernel_warn.rb
@@ -45,10 +45,9 @@ class << self
             end
           end
         end
-        uplevel = start
+        kw[:uplevel] = start
       end
 
-      kw[:uplevel] = uplevel
       original_warn.call(*messages, **kw)
     }
   end

From 4b0f57f2378abefd6fb82a53449a9e4d81183e76 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?David=20Rodr=C3=ADguez?= <deivid.rodriguez@riseup.net>
Date: Thu, 1 Oct 2020 14:56:36 +0200
Subject: [PATCH 2/2] Preserve `self` when calling the original Kernel#warn
 method

This fixes infinite recursion when monkey-patching Warning#warn, which
is not recommended, but still should behave the same whether RubyGems is
loaded or not.
---
 lib/rubygems/core_ext/kernel_warn.rb |  8 +++---
 test/rubygems/test_require.rb        | 41 ++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+), 4 deletions(-)

diff --git a/lib/rubygems/core_ext/kernel_warn.rb b/lib/rubygems/core_ext/kernel_warn.rb
index 3ed16c8cc7ed..b468813ce722 100644
--- a/lib/rubygems/core_ext/kernel_warn.rb
+++ b/lib/rubygems/core_ext/kernel_warn.rb
@@ -6,7 +6,7 @@
   module Kernel
     rubygems_path = "#{__dir__}/" # Frames to be skipped start with this path.
 
-    original_warn = method(:warn)
+    original_warn = instance_method(:warn)
 
     remove_method :warn
 
@@ -17,9 +17,9 @@ class << self
     module_function define_method(:warn) {|*messages, **kw|
       unless uplevel = kw[:uplevel]
         if Gem.java_platform?
-          return original_warn.call(*messages)
+          return original_warn.bind(self).call(*messages)
         else
-          return original_warn.call(*messages, **kw)
+          return original_warn.bind(self).call(*messages, **kw)
         end
       end
 
@@ -48,7 +48,7 @@ class << self
         kw[:uplevel] = start
       end
 
-      original_warn.call(*messages, **kw)
+      original_warn.bind(self).call(*messages, **kw)
     }
   end
 end
diff --git a/test/rubygems/test_require.rb b/test/rubygems/test_require.rb
index 70242a1f3c5e..d65b6c9527de 100644
--- a/test/rubygems/test_require.rb
+++ b/test/rubygems/test_require.rb
@@ -677,6 +677,47 @@ def test_require_bundler_with_bundler_version
         end
       end
     end
+
+    def test_no_crash_when_overriding_warn_with_warning_module
+      skip "https://github.com/oracle/truffleruby/issues/2109" if RUBY_ENGINE == "truffleruby"
+
+      Dir.mktmpdir("warn_test") do |dir|
+        File.write(dir + "/main.rb", "module Warning; def warn(str); super; end; end; warn 'Foo Bar'")
+        _, err = capture_subprocess_io do
+          system(*ruby_with_rubygems_in_load_path, "-w", "--disable=gems", "-C", dir, "main.rb")
+        end
+        assert_match(/Foo Bar\n$/, err)
+        _, err = capture_subprocess_io do
+          system(*ruby_with_rubygems_in_load_path, "-w", "--enable=gems", "-C", dir, "main.rb")
+        end
+        assert_match(/Foo Bar\n$/, err)
+      end
+    end
+
+    def test_expected_backtrace_location_when_inheriting_from_basic_object_and_including_kernel
+      Dir.mktmpdir("warn_test") do |dir|
+        File.write(dir + "/main.rb", "\nrequire 'sub'\n")
+        File.write(dir + "/sub.rb", <<-'RUBY')
+          require 'rubygems'
+          class C < BasicObject
+            include ::Kernel
+            def deprecated
+              warn "This is a deprecated method", uplevel: 2
+            end
+          end
+          C.new.deprecated
+        RUBY
+
+        _, err = capture_subprocess_io do
+          system(*ruby_with_rubygems_in_load_path, "-w", "--enable=gems", "-C", dir, "-I", dir, "main.rb")
+        end
+        assert_match(/main\.rb:2: warning: This is a deprecated method$/, err)
+        _, err = capture_subprocess_io do
+          system(*ruby_with_rubygems_in_load_path, "-w", "--enable=gems", "-C", dir, "-I", dir, "main.rb")
+        end
+        assert_match(/main\.rb:2: warning: This is a deprecated method$/, err)
+      end
+    end
   end
 
   private