avoid false const warnings (when using bundler)

[kares]

Bundler will load YAML and thus Psych, which causes versions.rb to be
required, but than it also loads the psych.gemspec ... (loading .rb twice)

in such case, the reported version constants might not be accurate
and also causes warnings due double loading of the same versions.rb

this is really annoying and the unless defined?(VERSION) is not really a good solution
(have been confused by the psych version used - depends on LOAD_PATH entries order)

[stomar]

I did not investigate into the problem this is supposed to solve (possibly a problem of bundler?), but parsing a Ruby file using regular expressions instead of simply require‘ing it seems really wrong. Also, the proposed change does not consider the special treatment necessary for the core repository.

[deivid-rodriguez]

This is interesting. We have this longstanding PR in bundler that seems to be somehow related. How can this problem be reproduced?

[kares]

any objections to merge this one?

[deivid-rodriguez]

I tried a better fix on #433 but I'm still unsure how to reliably reproduce these warnings... 🤔

[kares]

vaguely recall these came while doing day-to-day dev on JRuby and than installing a custom psych.
believe might have been trying out a dev built before releasing but kept on running into these with some of the test suite.

#433 might do - the gist of the changes were to not load any files from the gem while reading the spec and #433 keeps loading version.rb which than would be the source of confusion about the version used (if it gets loaded again as a bundled dependency). agree, should have had a reproducer.

[deivid-rodriguez]

Ok, I can reliably reproduce it now. Do gem install psych, so that you have a global version of psych installed, and then:

On master

$ rm Gemfile.lock && bundle
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by com.headius.backport9.modules.Modules to method sun.nio.ch.NativeThread.signal(long)
WARNING: Please consider reporting this to the maintainers of com.headius.backport9.modules.Modules
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
/home/deivid/.rbenv/versions/jruby-9.2.9.0/lib/ruby/stdlib/psych/versions.rb:8: warning: already initialized constant DEFAULT_SNAKEYAML_VERSION
Fetching gem metadata from https://rubygems.org/..................
Resolving dependencies...
Using rake 13.0.1
Using bundler 2.1.4
Using jar-dependencies 0.4.0
Using minitest 5.14.0
Using psych 3.1.0 (java) from source at `.`
  jar dependencies for psych-3.1.0-java.gemspec . . .
[DEPRECATED] `Bundler.with_clean_env` has been deprecated in favor of `Bundler.with_unbundled_env`. If you instead want the environment before bundler was originally loaded, use `Bundler.with_original_env` (called at /home/deivid/.rbenv/versions/jruby-9.2.9.0/lib/ruby/gems/shared/gems/ruby-maven-3.3.12/lib/ruby_maven.rb:38)
unsupported Java version "11", defaulting to 1.7
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.jruby.util.io.FilenoUtil (file:/home/deivid/.m2/repository/org/jruby/jruby-core/9.1.2.0/jruby-core-9.1.2.0.jar) to method sun.nio.ch.SelChImpl.getFD()
WARNING: Please consider reporting this to the maintainers of org.jruby.util.io.FilenoUtil
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
sh: 1: cd: can't cd to uri:classloader:/
      org.yaml:snakeyaml:1.23:compile
Using rake-compiler 1.1.0
Using ruby-maven-libs 3.3.9
Using ruby-maven 3.3.12
Bundle complete! 4 Gemfile dependencies, 8 gems now installed.
Use `bundle info [gemname]` to see where a bundled gem is installed.

On my branch

$ rm Gemfile.lock && bundle
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by com.headius.backport9.modules.Modules to method sun.nio.ch.NativeThread.signal(long)
WARNING: Please consider reporting this to the maintainers of com.headius.backport9.modules.Modules
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
Fetching gem metadata from https://rubygems.org/..................
Resolving dependencies...
Using rake 13.0.1
Using bundler 2.1.4
Using jar-dependencies 0.4.0
Using minitest 5.14.0
Using psych 3.1.0 (java) from source at `.`
  jar dependencies for psych-3.1.0-java.gemspec . . .
[DEPRECATED] `Bundler.with_clean_env` has been deprecated in favor of `Bundler.with_unbundled_env`. If you instead want the environment before bundler was originally loaded, use `Bundler.with_original_env` (called at /home/deivid/.rbenv/versions/jruby-9.2.9.0/lib/ruby/gems/shared/gems/ruby-maven-3.3.12/lib/ruby_maven.rb:38)
unsupported Java version "11", defaulting to 1.7
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.jruby.util.io.FilenoUtil (file:/home/deivid/.m2/repository/org/jruby/jruby-core/9.1.2.0/jruby-core-9.1.2.0.jar) to method sun.nio.ch.SelChImpl.getFD()
WARNING: Please consider reporting this to the maintainers of org.jruby.util.io.FilenoUtil
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
sh: 1: cd: can't cd to uri:classloader:/
      org.yaml:snakeyaml:1.23:compile
Using rake-compiler 1.1.0
Using ruby-maven-libs 3.3.9
Using ruby-maven 3.3.12
Bundle complete! 4 Gemfile dependencies, 8 gems now installed.
Use `bundle info [gemname]` to see where a bundled gem is installed.

The problem is that when loading the gemspec, bundler loads the versions.rb file relatively, but then bundler internally tries to load psych from the $LOAD_PATH and loads the globally installed version, causing the redefinition warnings.

I think it's fine to load the version file from the gemspec as #433 do. Most gems out there do it and it works fine. Note that it's only for "development", once a gem is pushed to rubygems.org and installed, the gemspec has the correct version and does not load any external files.

The only thing special about psych that is causing this warning is that it is loaded by bundler internally on bundle install. In this case, I think it's fine to modify the $LOAD_PATH for development of the psych gem inside the gemspec to force bundler to actually load the local version?

[kares]

Thanks for looking into it David, closing in favor of #433