1.2.x: Ensure that Rubygems is not unnecessarily initialized during boot and Gem.paths are left in consistent state#358
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chadlwilson merged 4 commits intojruby:1.2-stablefrom Oct 11, 2025
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…nt state As noted at jruby/warbler#575 for warbler, it is similarly possible for jruby-rack to leave ENV['GEM_PATH'] and Gem.path in an inconsistent state after it updates them. This would make any later Gem.clear_paths or Bundler usage (driven from the ENV vars) unpredictable. This happens because jruby-rack alters `ENV['GEM_PATH']``, in some cases but does not force Rubygems to recalculate Gem.paths. Normally this is fine, however if Gem.paths had already been used and cached prior to this mangling `Gem.path` will contain a "stale" value with respect to ENV. (e.g possibly missing the `GEM_HOME`/`Gem.default_dir` value, or retaining values from an old `GEM_PATH`. Clearing the paths is the only way to ensure things are consistent for later usage. In particular this currently can happen on JRuby 9.4+ because often `Gem.path` is already initialized by the time we boot, due to the use of default gems such as `stringio`. Rather than assume a given state, it would be better to ensure it is consistent by clearing paths whenever we touch `ENV['GEM_PATH']`.
…lse init parameter option Changes the `false` value to behave the same way as empty, and not touch ENV['GEM_PATH'] or Gem.path at all. Previously this allowed you to alter Gem.path without touching the ENV['GEM_PATH']'. This was unsafe with Bundler 1.6+ (so for a long time), because many things may cause Gem.path to be recalculated from env, including bundler initialisations, restarts and later changes within an application's boot hooks. Furthermore the behaviour varied wildly depending on whether Rubygems was initialised prior to the Rack booter, or afterwards, even without bundler causing indeterminism and issues similar to jruby/warbler#575 I cannot find any reference to use of this value on GitHub, or discussion, and it would not work at all with modern JRuby/bundler so removing it, because it helps avoid further issues. Note that it was added in jruby@2fd826b and then the default changed back in jruby@d3ee8f0 shortly after when issues were discovered, so given it's undocumented/unsupported, it is unlikely to be relied upon by anyone.
On JRuby 9.4 this causes Rubygems initialisation which means realisation of init values. This screws with jruby-rack's own guarantees about env implied by its config values and can cause issues in boot hooks such as jruby/warbler#575 due to Rubygems being in a different state to what they expect.
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As noted in jruby/warbler#575, jruby-rack can leave
ENV['GEM_PATH']andGem.pathin an inconsistent state.This change
require 'stringio'in ourcore_extdebugging monkey patches.jruby.rack.env.gem_pathto updateGEM_PATHENV['GEM_PATH']ever needs to be updated with a relative gem path. (Default is true) This makes things safer in the case that we end up doing early initialization for some other reason than thestringiorequire, in future.jruby.rack.env.gem_path=falsecapability, which updated path directly and didn't touch env. This one always would break warbler, and don't see any reference to people using it. Warbler has its own separate approach.Also manually tested this with current warbler master, and validated it fixes the issues linked to/discussed in jruby/warbler#575