loading jruby ext can fail with NullPointerException

[kares]

in an embedded use-case (e.g. with jar-dependencies instructed to use the snakeyaml from the parent class-path)
the input stream (for META-INF/maven/org.snakeyaml/snakeyaml-engine/pom.properties) can easily end up as null:

NameError: cannot load (ext) (org.jruby.ext.psych.PsychLibrary)
  org/jruby/ext/jruby/JRubyUtilLibrary.java:219:in `load_ext'
  uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/psych.rb:9:in `<main>'
  org/jruby/RubyKernel.java:1187:in `require'
  uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/rubygems/core_ext/kernel_require.rb:148:in `require'
  uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/rubygems.rb:610:in `load_yaml'
  uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/rubygems/package.rb:549:in `read_checksums'
  uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/rubygems/package.rb:611:in `block in verify'
  uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/rubygems/package/tar_reader.rb:27:in `new'
  uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/rubygems/package.rb:610:in `block in verify'
  org/jruby/RubyIO.java:1198:in `open'
  uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/rubygems/package/file_source.rb:29:in `with_read_io'
  uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/rubygems/package.rb:609:in `verify'
  uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/rubygems/package.rb:590:in `spec'
  uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/bundler/rubygems_integration.rb:208:in `spec_from_gem'
  uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/bundler/runtime.rb:218:in `block in prune_gem_cache'
  org/jruby/RubyArray.java:3149:in `delete_if'
  uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/bundler/runtime.rb:217:in `prune_gem_cache'
  uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/bundler/runtime.rb:144:in `prune_cache'
  uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/bundler/runtime.rb:136:in `cache'
  uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/bundler/cli/install.rb:65:in `block in run'
  uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/bundler/settings.rb:131:in `temporary'
  uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/bundler/cli/install.rb:64:in `run'
  uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/bundler/cli.rb:257:in `block in install'
  uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/bundler/settings.rb:131:in `temporary'
  uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/bundler/cli.rb:256:in `install'
  uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/bundler/vendor/thor/lib/thor/command.rb:27:in `run'
  uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/bundler/vendor/thor/lib/thor/invocation.rb:127:in `invoke_command'
  uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/bundler/vendor/thor/lib/thor.rb:392:in `dispatch'
  uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/bundler/cli.rb:31:in `dispatch'
  uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/bundler/vendor/thor/lib/thor/base.rb:485:in `start'
  uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/bundler/cli.rb:25:in `start'
  bin/bundle:33:in `block in <main>'
  uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/bundler/friendly_errors.rb:120:in `with_friendly_errors'
  bin/bundle:25:in `<main>'
Java::JavaLang::NullPointerException: inStream parameter is null
  java.base/java.util.Objects.requireNonNull(Objects.java:246)
  java.base/java.util.Properties.load(Properties.java:406)
  org.jruby.ext.psych.PsychLibrary.load(PsychLibrary.java:57)
  org.jruby.ext.jruby.JRubyUtilLibrary.loadExtension(JRubyUtilLibrary.java:242)
  org.jruby.ext.jruby.JRubyUtilLibrary.load_ext(JRubyUtilLibrary.java:219)
  org.jruby.ext.jruby.JRubyUtilLibrary$INVOKER$s$1$0$load_ext.call(JRubyUtilLibrary$INVOKER$s$1$0$load_ext.gen)
  org.jruby.runtime.callsite.CachingCallSite.cacheAndCall(CachingCallSite.java:466)
  org.jruby.runtime.callsite.CachingCallSite.call(CachingCallSite.java:244)
  org.jruby.ir.interpreter.InterpreterEngine.processCall(InterpreterEngine.java:314)
  org.jruby.ir.interpreter.StartupInterpreterEngine.interpret(StartupInterpreterEngine.java:66)
  org.jruby.ir.interpreter.Interpreter.INTERPRET_ROOT(Interpreter.java:98)
  org.jruby.ir.interpreter.Interpreter.execute(Interpreter.java:83)
  org.jruby.ir.interpreter.Interpreter.execute(Interpreter.java:32)
  org.jruby.ir.IRTranslator.execute(IRTranslator.java:41)
  org.jruby.Ruby.runInterpreter(Ruby.java:1269)
  org.jruby.Ruby.loadFile(Ruby.java:3060)

and extra != null check should be added https://github.com/ruby/psych/blob/master/ext/java/org/jruby/ext/psych/PsychLibrary.java#L57

[headius]

Looks like this is some original code from way back. I will have time to dig into this more after FOSDEM.

Do you think the null check and fallback would be sufficient?

[kares]

Should be sufficient (there's already fallback for IOException), the down side is going to be a "invalid" 0.0 snakeyaml version constant.