[fix] Ensure that jruby-rack leaves ENV vars and Gem.path in consistent state #23
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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']`.
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…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 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 manglingGem.pathwill contain a "stale" value with respect to ENV. (e.g possibly missing theGEM_HOME/Gem.default_dirvalue, or retaining values from an oldGEM_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.pathis already initialized by the time we boot, due to the use of default gems such asstringio. Rather than assume a given state, it would be better to ensure it is consistent by clearing paths whenever we touchENV['GEM_PATH'].