eregon/ractor-shim

Ractor-shim is a small Ruby gem that lets code written for Ruby's Ractor feature run on Ruby versions or implementations that don't natively support Ractors. Ractors are Ruby's relatively new way to run code in true parallel, but not every Ruby environment includes them. This gem fills that gap so the same code can work everywhere without modification. At a high level, it recreates the Ractor API using Ruby's older building blocks: threads and queues. If your Ruby environment already has Ractors built in, the gem steps aside and does nothing. If it doesn't, the gem defines a compatible version of Ractor using those underlying threading tools. It also provides a preview of the upcoming Ruby 4.0 Ractor API for current standard Ruby versions (2.7 through 3.4), so you can write code against the newer interface before it officially ships. This is useful for developers building Ruby applications that need to run across different Ruby implementations, for example, someone writing a library that uses Ractors but wants it to also work on TruffleRuby or JRuby, which run Ruby code in parallel threads rather than using native Ractors. Without this gem, code that calls Ractor.new would simply crash on those platforms. With it, the same code runs, taking advantage of the parallel threading those implementations already provide. One notable tradeoff: when Ractors aren't natively available, the gem's version of Ractor.make_shareable, a method normally used to safely share objects between parallel workers, simply returns the object unchanged. This skips the usual deep-freezing step for performance reasons, reasoning that the standard behavior makes objects immutable anyway, so there's no practical risk. This keeps things fast but relies on code being well-behaved.