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JRuby

The Ruby Programming Language on the JVM

This document serves as a getting-started guide for those wishing to use Sorbet with JRuby.

The use of Sorbet on the JVM is NOT SUPPORTED by the Sorbet development team however this document services as a getting started guide for those who wish to trot on a unsupported path.

Any bug reports that only reproduce on JRuby are likely to not get fixed or potentially even closed.

Performance

TBD

Gotchas

RBI for Java Code

The srb tool can auto-generate RBI files for your gems however it cannot do so for your Java code.

The technical reason is because the Java code is never officially required so that it never ends up being triggered through TracePoint

To move past the woes of the type-checker, the following hand curated pattern for Java RBI files has worked well:

tree ./sorbet
|------ config
|------ rbi
    |-------- java
    |   |---------- java_lang.rbi # this is the standard library
    |   |---------- org_eclipse_jgit.rbi
    |   |---------- org_apache_logging_log4j.rbi
    |-------------  org_slf4j.rbi

Essentially, take the maven coordinates for a given java package (replaced with underscores) and hand-create an RBI file for it.

Put as much as you need depending on the # typed: sigils you are aiming for.

# typed: strong

module Java

  module OrgEclipseJgitApiErrors

    class JGitInternalException < Exception

    end

  end

end

Installing sorbet-static

You might have added sorbet to your Gemfile but noticed that sorbet-static was not included and that srb failed!

This is because at the moment the Sorbet team does not publish a sorbet-static gem for the Java platform.

The workaround is to fetch the Gem manually for your arch and install it.

For instance on macOS you would do:

# download the most recent one
gem fetch sorbet-static --platform universal-darwin
# install it from the local file
gem install --local sorbet-static-*-universal-darwin-*.gem

Debug Flag

When running the srb command to generate RBI files for any gems, you may depend on -- make sure to have the --debug flag enabled.

jruby --debug srb rbi gems

Sorbet relies on TracePoint to discover modules & classes, which is disabled by default in JRuby unless the flag is enabled.

For good measure you can set the following

jruby -J-Djruby.objectspace.enabled=true -J-Djruby.compile.mode=OFF \
       -J-Djruby.debug.fullTrace=true --debug srb rbi gems

Naming Convention For Java code

You can reference a Java class in JRuby in a couple of different ways.

Java: org.foo.department.Widget
Ruby: Java::OrgFooDepartment::Widget

You can even leverage java_import and then access the class non fully qualified.

Unfortunately, Sorbet will not be able to resolve many of these ways and the only course of action is to take fully-qualify the code and transform the name by removing the dots and converting to CamelCase.

If you don't, Sorbet will think that Java class use such as org.foo.department.Widget are a series of method calls.