Environment

jruby 9.2.4.0 (2.5.0) 2018-11-13 8faff06 Java HotSpot(TM) 64-Bit Server VM 10.0.1+10 on 10.0.1+10 +jit [darwin-x86_64]

Issue

JRuby 9.2.4.0 uses the stdlib version of ERB from MRI 2.5.0. Unfortunately, that version introduced a backwards-incompatible change, as documented in https://redmine.ruby-lang.org/issues/14243. The change was reverted in MRI 2.5.1.

FWIW I tried the current trunk version of ERB instead and it seemed to work fine with JRuby 9.2.4.0.

I'm not sure what the JRuby policy is for updating the stdlib, but I'm guessing it's to match the compatibility version that's reported with jruby -v. That would rule out just updating ERB to the 2.5.1 version.

So I suppose this ticket is just a little bit of motivation to update to the latest 2.5.x stdlib :)