[ruby/bigdecimal] Stub out extension build on JRuby

JRuby currently ships its own internal bigdecimal extension as
part of the core libraries. In order for users to be able to add
bigdecimal to their Gemfile or gem dependencies, we need to stub
out the C extension and just load the extension shipped with
JRuby.

In the future we will try to move our BigDecimal implementation
into the gem, but for now this is the simplest way to make it
installable on JRuby.

See #169

https://github.com/ruby/bigdecimal/commit/829956c643

2 files changed, 20 insertions, 10 deletions

diff --git a/ext/bigdecimal/bigdecimal.gemspec b/ext/bigdecimal/bigdecimal.gemspec
index d215757188..b05b2b0891 100644
--- a/ext/bigdecimal/bigdecimal.gemspec
+++ b/ext/bigdecimal/bigdecimal.gemspec
@@ -12,17 +12,8 @@ Gem::Specification.new do |s|
   s.licenses       = ["Ruby", "bsd-2-clause"]
 
   s.require_paths = %w[lib]
-  s.extensions    = %w[ext/bigdecimal/extconf.rb]
   s.files         = %w[
     bigdecimal.gemspec
-    ext/bigdecimal/bigdecimal.c
-    ext/bigdecimal/bigdecimal.h
-    ext/bigdecimal/bits.h
-    ext/bigdecimal/feature.h
-    ext/bigdecimal/missing.c
-    ext/bigdecimal/missing.h
-    ext/bigdecimal/missing/dtoa.c
-    ext/bigdecimal/static_assert.h
     lib/bigdecimal.rb
     lib/bigdecimal/jacobian.rb
     lib/bigdecimal/ludcmp.rb
@@ -33,6 +24,21 @@ Gem::Specification.new do |s|
     sample/nlsolve.rb
     sample/pi.rb
   ]
+  if Gem::Platform === s.platform and s.platform =~ 'java' or RUBY_ENGINE == 'jruby'
+    s.platform      = 'java'
+  else
+    s.extensions    = %w[ext/bigdecimal/extconf.rb]
+    s.files += %w[
+      ext/bigdecimal/bigdecimal.c
+      ext/bigdecimal/bigdecimal.h
+      ext/bigdecimal/bits.h
+      ext/bigdecimal/feature.h
+      ext/bigdecimal/missing.c
+      ext/bigdecimal/missing.h
+      ext/bigdecimal/missing/dtoa.c
+      ext/bigdecimal/static_assert.h
+    ]
+  end
 
   s.required_ruby_version = Gem::Requirement.new(">= 2.5.0")
 end
diff --git a/ext/bigdecimal/lib/bigdecimal.rb b/ext/bigdecimal/lib/bigdecimal.rb
index 8fd2587c84..82b3e1b7b9 100644
--- a/ext/bigdecimal/lib/bigdecimal.rb
+++ b/ext/bigdecimal/lib/bigdecimal.rb
@@ -1 +1,5 @@
-require 'bigdecimal.so'
+if RUBY_ENGINE == 'jruby'
+  JRuby::Util.load_ext("org.jruby.ext.bigdecimal.BigDecimalLibrary")
+else
+  require 'bigdecimal.so'
+end