This is a backport of the no-inspect NameError logic added to JRuby 10 in #8533, guarded by an option for users on JRuby 9.4.

On 9.4, the inspect logic is enabled by default, but can be disabled by with the option -XnameError.inspect.object=false. Because the object inspect is a specified behavior of Ruby 3.1, we can't disable it by default, but this allows users to opt out of the behavior.

JRuby 10 will ignore this logic and avoid inspecting the object attached to the NameError. The option will have no effect.

Using the example from #8384 with this new option:

$ jruby -w -J-Xmx250M -XnameError.inspect.object=false blah.rb
generating large obj
done
NameError: undefined local variable or method `nameerror' for an instance of Test
   error at blah.rb:9
  <main> at blah.rb:16

Interestingly, I discovered that the original code does not OOM on Java 21, because it never seems to call the expected inspect method. I will open an issue to investigate that.

I realized that when I reproduced this it was Java 21 BUT also it was JRuby 10. I also cannot reproduce with Java 21 on 9.4. If I had to guess my TC refactoring for inspect() "fixed" it.

./bin/jruby -vw -J-Xmx250M ../snippets/name1.rb 
jruby 10.0.0.0-SNAPSHOT (3.4.0) 2024-12-19 7554ac66ab OpenJDK 64-Bit Server VM 21.0.5+11-LTS on 21.0.5+11-LTS +indy +jit [x86_64-linux]
uri:classloader:/jruby/kernel/data.rb:64: warning: ambiguity between regexp and two divisions: wrap regexp in parentheses or add a space after `/' operator
generating large obj
done
Error: Your application used more memory than the safety cap of 250M.
Specify -J-Xmx####M to increase it (#### = cap size in MB).
java.lang.OutOfMemoryError: Java heap space

Ok I think it's just that 21 is a bit more memory efficient, so it's able to handle this case in 250MB. I lowered it to 225MB and it fails like Java 8.

$ jruby -v -J-Xmx225M blah.rb
jruby 9.4.10.0-SNAPSHOT (3.1.4) 2025-01-15 2f915ca63d OpenJDK 64-Bit Server VM 21.0.5+11-LTS on 21.0.5+11-LTS +jit [arm64-darwin]
generating large obj
done
Error: Your application used more memory than the safety cap of 225M.
Specify -J-Xmx####M to increase it (#### = cap size in MB).
java.lang.OutOfMemoryError: Java heap space

Good to merge for 9.4.10.