[GR-21161] Make require 'rubygems/specification' work before require 'rubygems'.

PullRequest: truffleruby/1750

Author: eregon

CHANGELOG.md

@@ -30,6 +30,7 @@ Bug fixes:
 * Fix missing flushing when printing an exception at top-level with a custom backtrace, which caused no output being shown (#1750, #1895).
 * Use the mode of the given `IO` for `IO#reopen(IO)` which is important for the 3 standard IOs (#2034).
 * Fix potential deadlock when running finalizers (#2041).
+* Let `require 'rubygems/specification'` work before `require 'rubygems'`.
 
 Compatibility:
 

lib/patches/rubygems/specification.rb

@@ -0,0 +1,13 @@
+# rubygems/specification.rb is required by rubygems.rb.
+# require "rubygems/specification" only works on MRI if RubyGems is
+# already loaded (and is a no-op), and fails with --disable-gems.
+# On TruffleRuby with lazy RubyGems, Gem is an autoload.
+# So if we are in that case, just require 'rubygems' instead,
+# as if RubyGems was loaded eagerly on startup.
+
+if Object.autoload?(:Gem) # lazy-rubygems enabled, rubygems.rb was not yet loaded
+  require 'rubygems'
+  raise 'Gem::Specification should have been defined' unless defined?(Gem::Specification)
+else
+  require 'rubygems/specification'
+end

spec/tags/truffle/lazy_rubygems_tags.txt

@@ -3,3 +3,4 @@ slow:RubyGems is loaded when accessing Gem
 slow:RubyGems is loaded by a failing require
 slow:Lazy RubyGems defines StringIO like RubyGems which requires it eagerly
 slow:Lazy RubyGems works for require 'rubygems/package'
+slow:Lazy RubyGems works for require 'rubygems/specification'

spec/truffle/lazy_rubygems_spec.rb

@@ -36,4 +36,8 @@
   it "works for require 'rubygems/package'" do
     ruby_exe("require 'rubygems/package'; p Gem::Package").should == "Gem::Package\n"
   end
+
+  it "works for require 'rubygems/specification'" do
+    ruby_exe("require 'rubygems/specification'; p Gem::Specification").should == "Gem::Specification\n"
+  end
 end