kernel_warn.rb: skip kernel_require.rb

* lib/rubygems/core_ext/kernel_warn.rb (Kernel#warn): skip
  kernel_require.rb's frames when `uplevel` option is given.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64817 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/rubygems.rb

@@ -1392,5 +1392,6 @@ Gem::Specification.load_defaults
 
 require 'rubygems/core_ext/kernel_gem'
 require 'rubygems/core_ext/kernel_require'
+require 'rubygems/core_ext/kernel_warn'
 
 Gem.use_gemdeps

lib/rubygems/core_ext/kernel_warn.rb

@@ -0,0 +1,21 @@
+# frozen_string_literal: true
+
+if RUBY_VERSION >= "2.5"
+  module Kernel
+    path = "#{__dir__}/"
+    original_warn = instance_method(:warn)
+    Module.new {define_method(:warn, original_warn)}
+    original_warn = method(:warn)
+
+    module_function define_method(:warn) {|message, uplevel: nil|
+      if uplevel
+        while (loc, = caller_locations(uplevel, 1); loc && loc.path.start_with?(path))
+          uplevel += 1
+        end
+        original_warn.call(message, uplevel: uplevel + 1)
+      else
+        original_warn.call(message)
+      end
+    }
+  end
+end

test/rubygems/test_require.rb

@@ -412,6 +412,24 @@ class TestGemRequire < Gem::TestCase
     end
   end
 
+  if RUBY_VERSION >= "2.5"
+    def test_no_kernel_require_in_warn_with_uplevel
+      lib = File.realpath("../../../lib", __FILE__)
+      Dir.mktmpdir("warn_test") do |dir|
+        File.write(dir + "/sub.rb", "warn 'uplevel test', uplevel: 2\n")
+        File.write(dir + "/main.rb", "require 'sub'\n")
+        _, err = capture_subprocess_io do
+          system(@@ruby, "-w", "--disable=gems", "-I", lib, "-C", dir, "-I.", "main.rb")
+        end
+        assert_equal "main.rb:1: warning: uplevel test\n", err
+        _, err = capture_subprocess_io do
+          system(@@ruby, "-w", "--enable=gems", "-I", lib, "-C", dir, "-I.", "main.rb")
+        end
+        assert_equal "main.rb:1: warning: uplevel test\n", err
+      end
+    end
+  end
+
   def silence_warnings
     old_verbose, $VERBOSE = $VERBOSE, false
     yield