Set RbConfig::CONFIG['ruby_version'] to the TruffleRuby version

* See #1715
* Fix path to bundled gems inside the TruffleRuby home.

Author: eregon

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 Bug fixes:
 
+* Set `RbConfig::CONFIG['ruby_version']` to the same value as the TruffleRuby version. This fixes reusing C extensions between different versions of TruffleRuby with Bundler (#1715).
 * Fixed `Symbol#match` returning `MatchData` (#1706).
 * Allow `Time#strftime` to be called with binary format strings.
 

lib/truffle/rbconfig.rb

@@ -49,7 +49,10 @@ module RbConfig
   ruby_install_name = 'truffleruby'
 
   ruby_base_name = 'ruby'
-  ruby_version   = Truffle::RUBY_BASE_VERSION
+
+  # The full TruffleRuby version, so C extensions from one TruffleRuby version
+  # are not reused with another TruffleRuby version.
+  ruby_abi_version = RUBY_ENGINE_VERSION
 
   arch     = "#{host_cpu}-#{host_os}"
   libs     = ''
@@ -96,7 +99,7 @@ module RbConfig
     'RUBY_BASE_NAME'    => ruby_base_name,
     'ruby_install_name' => ruby_install_name,
     'RUBY_INSTALL_NAME' => ruby_install_name,
-    'ruby_version'      => ruby_version,
+    'ruby_version'      => ruby_abi_version,
     'target_cpu'        => host_cpu,
     'target_os'         => host_os,
   }
@@ -160,8 +163,9 @@ module RbConfig
     sitedir = \
     expanded['sitedir'] = "#{rubylibprefix}/site_ruby"
     mkconfig['sitedir'] = '$(rubylibprefix)/site_ruby'
+    # Must be kept in sync with post.rb
     sitelibdir = \
-    expanded['sitelibdir'] = "#{sitedir}/#{ruby_version}"
+    expanded['sitelibdir'] = "#{sitedir}/#{ruby_abi_version}"
     mkconfig['sitelibdir'] = '$(sitedir)/$(ruby_version)'
     expanded['sitearchdir'] = "#{sitelibdir}/#{sitearch}"
     mkconfig['sitearchdir'] = '$(sitelibdir)/$(sitearch)'

lib/truffle/rubygems/defaults/truffleruby.rb

@@ -1,2 +1,19 @@
-# Empty file to avoid raising a LoadError while loading RubyGems
-# Lazy RubyGems also relies on this
+# frozen_string_literal: true
+
+# Copyright (c) 2019 Oracle and/or its affiliates. All rights reserved. This
+# code is released under a tri EPL/GPL/LGPL license. You can use it,
+# redistribute it and/or modify it under the terms of the:
+#
+# Eclipse Public License version 1.0, or
+# GNU General Public License version 2, or
+# GNU Lesser General Public License version 2.1.
+
+# Defaults for RubyGems when running on TruffleRuby.
+# This file is required by RubyGems when RubyGems is loaded.
+
+module Gem
+  # The path to the gems shipped with TruffleRuby
+  def self.default_dir
+    @default_dir ||= "#{Truffle::Boot.ruby_home or raise 'TruffleRuby home not found'}/lib/ruby/gems/#{Truffle::RUBY_BASE_VERSION}"
+  end
+end

spec/truffle/identity_spec.rb

@@ -67,8 +67,8 @@
     RbConfig::CONFIG['RUBY_INSTALL_NAME'].should == 'truffleruby'
   end
 
-  it "RbConfig::CONFIG['ruby_version'] matches RUBY_VERSION except with the minor always being zero" do
-    RbConfig::CONFIG['ruby_version'].should == RUBY_VERSION.sub(/\.(\d+)\z/, '.0')
+  it "RbConfig::CONFIG['ruby_version'] is the ABI version and matches RUBY_ENGINE_VERSION" do
+    RbConfig::CONFIG['ruby_version'].should == RUBY_ENGINE_VERSION
   end
 
   it "RbConfig::CONFIG['RUBY_BASE_NAME'] is 'ruby'" do

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

@@ -102,8 +102,9 @@ def p(*a)
 ruby_home = Truffle::Boot.ruby_home
 if ruby_home
   # Does not exist but it's used by rubygems to determine index where to insert gem lib directories, as a result
-  # paths supplied by -I will stay before gem lib directories.
-  $LOAD_PATH.push "#{ruby_home}/lib/ruby/site_ruby/#{Truffle::RUBY_BASE_VERSION}"
+  # paths supplied by -I will stay before gem lib directories. See Gem.load_path_insert_index in rubygems.rb.
+  # Must be kept in sync with the value of RbConfig::CONFIG['sitelibdir'].
+  $LOAD_PATH.push "#{ruby_home}/lib/ruby/site_ruby/#{RUBY_ENGINE_VERSION}"
 
   $LOAD_PATH.push "#{ruby_home}/lib/truffle"
   $LOAD_PATH.push "#{ruby_home}/lib/mri"