Engine: Preserve line count for ERB comment lines

[joelhawksley]

ERB comment lines (<%# ... %>) were stripped from compiled output, producing fewer lines than Erubi. This causes misattributed error locations when compiled templates are evaluated with module_eval and a line offset.

Erubi emits a blank line for each comment, preserving line numbering. Herb stripped them entirely.

Fix: Emit a blank code line ([:code, "\n", ...]) when processing standalone ERB comments at line start.

[joelhawksley]

Moving back to draft mode while I re-validate against 0.9.3.

[marcoroth]

@joelhawksley I'm happy to merge this, but just want to understand: The evaluated output was already correct and this is about more about "cosmetics", right?

[marcoroth]

Actually, does Erubi really try to make an effort to keep the code on the same line as it was in the source?

[joelhawksley]

@marcoroth As it turns out, we didn't need this change to pass CI. We are green on 0.9.4! I still think it's a good idea though, as it's nice to have error messages raised on the same lines as the original template file.

[marcoroth]

@joelhawksley awesome, that's great to hear and thanks for sharing! 🎉

I agree, it would be nice to have it aligned and behave the same way. Is there a reason why you closed #1556? Doesn't that serve a similar purpose?

[joelhawksley]

@marcoroth I closed #1556 because I didn't need it to pass CI. I left this one open because you commented on it ❤️

I'll let you decide whether to take any of them 😄

[marcoroth]

Oh my bad then, I only commented on one because they looked so similar. But if #1556 is actually also valid on its own then lets re-open it 🙌🏼