Add RubyFeatures.ripper_supported?

Author: yujinakayama

Changelog.md

@@ -5,6 +5,7 @@ Enhancements:
 * Improve formatting of `Delegator` based objects (e.g. `SimpleDelgator`) in
   failure messages and diffs. (Andrew Horner, #215)
 * Add `ComparableVersion`. (Yuji Nakayama, #245)
+* Add `Ripper` support detection. (Yuji Nakayama, #245)
 
 Bug Fixes:
 

benchmarks/ripper.rb

@@ -0,0 +1,44 @@
+require 'benchmark/ips'
+require 'ripper'
+
+ruby_version = defined?(JRUBY_VERSION) ? JRUBY_VERSION : RUBY_VERSION
+puts "#{RUBY_ENGINE} #{ruby_version}"
+
+source = File.read(__FILE__)
+
+Benchmark.ips do |x|
+  x.report("Ripper") do
+    Ripper.sexp(source)
+    Ripper.lex(source)
+  end
+end
+
+__END__
+
+ruby 1.9.3
+Calculating -------------------------------------
+              Ripper   284.000  i/100ms
+
+ruby 2.2.3
+Calculating -------------------------------------
+              Ripper   320.000  i/100ms
+
+jruby 1.7.5
+Calculating -------------------------------------
+              Ripper    24.000  i/100ms
+
+jruby 1.7.13
+Calculating -------------------------------------
+              Ripper    25.000  i/100ms
+
+jruby 1.7.14
+Calculating -------------------------------------
+              Ripper   239.000  i/100ms
+
+jruby 1.7.22
+Calculating -------------------------------------
+              Ripper   231.000  i/100ms
+
+jruby 9.0.1.0
+Calculating -------------------------------------
+              Ripper   218.000  i/100ms

lib/rspec/support/ruby_features.rb

@@ -1,4 +1,5 @@
 require 'rbconfig'
+RSpec::Support.require_rspec_support "comparable_version"
 
 module RSpec
   module Support
@@ -65,6 +66,24 @@ def supports_exception_cause?
         end
       end
 
+      ripper_requirements = [ComparableVersion.new(RUBY_VERSION) >= '1.9.2']
+
+      if Ruby.jruby?
+        ripper_requirements.push(ComparableVersion.new(JRUBY_VERSION) >= '1.7.5')
+        # Ripper on JRuby 9.0.0.0.rc1 or later reports wrong line number.
+        ripper_requirements.push(ComparableVersion.new(JRUBY_VERSION) < '9.0.0.0.rc1')
+      end
+
+      if ripper_requirements.all?
+        def ripper_supported?
+          true
+        end
+      else
+        def ripper_supported?
+          false
+        end
+      end
+
       if Ruby.mri?
         def kw_args_supported?
           RUBY_VERSION >= '2.0.0'

spec/rspec/support/ruby_features_spec.rb

@@ -81,6 +81,12 @@ module Support
           expect(RubyFeatures.caller_locations_supported?).to eq(RUBY_VERSION >= '2.0.0')
         end
       end
+
+      describe "#ripper_supported?" do
+        it 'does not load Ripper' do
+          expect { RubyFeatures.ripper_supported? }.not_to change { defined?(::Ripper) }
+        end
+      end
     end
   end
 end