[ruby] Add Support for ERB files

[AndreiDreyer]

• Added support for ERB files
• Added templateOutRaw (<%== %>) and templateOutEscape (<%= %>) operator calls
• Added RETURN for the joern__buffer which holds all of the appended strings from the ERB lowering
• Added .html.erb files as config files

[DavidBakerEffendi]

Nice

[maltek]

I'm still missing a lot of .erb files. E.g. for https://github.com/chatwoot/chatwoot:

ocular> cpg.file.name(".*.html.erb").size
val res18: Int = 40

ocular> cpg.configFile.name(".*.html.erb").size
val res19: Int = 88

The frontend spits out some warnings for the project, e.g. Yield expression outside of method scope: yield(:head) and Type 'String' is considered a 'core' type, not a 'Kernel-contained' type - but not enough to explain 48 missing files.

[AndreiDreyer]

@maltek these are the new results on chatwoot with all of the changes made for ERB handling.

joern> cpg.configFile.name(".*.html.erb").l.map(_.name).l.diff(cpg.file.name(".*.html.erb").map(_.name).l)
val res1: List[String] = List()

joern> cpg.file.name(".*.html.erb").l.size
val res2: Int = 88

joern> cpg.configFile.name(".*.html.erb").l.size
val res3: Int = 88

[ml86]

Why are you writing tests that include the lowering of a ruby AST into CPG?
The ERB support takes input ERB files and emits ruby code that is then fed into rubyAstGen. For the later part we already have plenty of tests. Here it would be much better readable if you test the first step ( ERB -> ruby code) the added benefit would be much better readability.

[DavidBakerEffendi]

ERB -> Ruby code is tested on the ruby_ast_gen project e.g., https://github.com/joernio/ruby_ast_gen/blob/main/spec/ruby_ast_gen_spec.rb#L155

Albeit, one could argue for more tests there perhaps, but we haven't designed the RubyAstGen hook to give us the lowered ERB code as-is, only via AST