[GR-18163] Set @gem_prelude_index variable on the default load paths

PullRequest: truffleruby/3157

Author: bjfish

CHANGELOG.md

@@ -25,6 +25,7 @@ Compatibility:
 * Add patch for `digest` so that TruffleRuby implementation is not overridden (@bjfish).
 * Handle encoding conversion errors when reading directory entries (@aardvark179).
 * Follow symlinks when processing `*/` directory glob patterns. (#2589, @aardvark179).
+* Set `@gem_prelude_index` variable on the default load paths (#2586 , @bjfish)
 
 Performance:
 

spec/ruby/language/predefined_spec.rb

@@ -835,6 +835,8 @@ def obj.foo2; yield; end
   it "can be changed via <<" do
     $: << "foo"
     $:.should include("foo")
+  ensure
+    $:.delete("foo")
   end
 
   it "is read-only" do
@@ -850,6 +852,14 @@ def obj.foo2; yield; end
       $-I = []
     }.should raise_error(NameError)
   end
+
+  it "default $LOAD_PATH entries until sitelibdir included have @gem_prelude_index set" do
+    $:.should.include?(RbConfig::CONFIG['sitelibdir'])
+    idx = $:.index(RbConfig::CONFIG['sitelibdir'])
+
+    $:[idx..-1].all? { |p| p.instance_variable_defined?(:@gem_prelude_index) }.should be_true
+    $:[0...idx].all? { |p| !p.instance_variable_defined?(:@gem_prelude_index) }.should be_true
+  end
 end
 
 describe "Global variable $\"" do

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

@@ -102,6 +102,8 @@ def p(*a)
     $LOAD_PATH.push "#{ruby_home}/lib/truffle"
     $LOAD_PATH.push "#{ruby_home}/lib/mri"
     $LOAD_PATH.push "#{ruby_home}/lib/json/lib"
+
+    $LOAD_PATH.each { |p| p.instance_variable_set(:@gem_prelude_index, p) }
   end
 end