Ruby -c does not detect unsupported syntax (false positive)

[sempervictus]

Running /usr/lib/jvm/java-21-graalvm/bin/ruby -c somefile.rb produces Syntax OK despite the file containing pattern-matching case statements which the interpreter cannot resolve (syntax error, unexpected keyword_in). This creates a false positive for tests trying to ensure that the resulting application is TruffleRuby-compatible.

[sempervictus]

This seems a bit more nefarious than i previously thought - https://github.com/oracle/truffleruby/blob/master/doc/user/compatibility.md does not seem to mention the whole "TruffleRuby doesnt do pattern matches" piece which is a pretty big deal especially when the interpreter validates the syntax.

Is there an effort somewhere to get this working?

[eregon]

ruby -c is a very weak check, in fact it only runs the parser but the not the compiler (from parser AST to another AST or to bytecode).
A simple example:

$ ruby -v -e 'break'
ruby 3.2.2 (2023-03-30 revision e51014f9c0) [x86_64-linux]
-e:1: Invalid break
-e: compile error (SyntaxError)

$ ruby -v -c -e 'break'
ruby 3.2.2 (2023-03-30 revision e51014f9c0) [x86_64-linux]
Syntax OK

And the fact is the current parser can parse pattern matching but it's not fully implemented yet (#3332) so that specific result is expected and -c basically should be like it is for compatibility with CRuby.

Indeed, https://github.com/oracle/truffleruby/blob/master/doc/user/compatibility.md misses to mention that, I will update it. Array pattern matching is already supported with the --pattern-matching flag, hash pattern matching not yet, we'll finish #3117 first.

[eregon]

Docs updated in e16a0c2

[sempervictus]

Thank you for the detailed explanation - looking forward to common parser and full(ish) compatibility with MRI syntax. Been a while since i've been free of the GIL in production.

[eregon]

Fixed for 24.0