Fix ERB expression compilation when code contains a heredoc

[pinzonjulian]

I attempted to use Reactionview in Buildkite's Rails monolith and found a blocking issue related to Heredocs.

When an ERB output tag wraps code in parentheses and that code contains a heredoc:

some_method, <<~A_HEREDOC, some_methods_attributes
  contents
  of
  the heredoc
A HEREDOC

the closing parenthesis must appear on its own line after the heredoc terminator. Without this, the compiled Ruby is syntactically invalid.

This is my first time diving into herb and reactionview so I relied quite a bit on AI for this as I get more comfortable. However, I reviewed the code thoroughly and tested it in CI in Buildkite where I was able to reduce failed specs from ~700 to ~60.

This is a sibling commit of marcoroth/herb#1206

[marcoroth]

I wonder if we could just assume to always add a newline, no matter what:

Suggested change

	@src << "(" << code
	@src << "\n" if code.match?(/<<[~-]?\s*['"`]?\w/)
	@src << ")"
	@src << "(" << code << "\n)"

[pinzonjulian]

Let me try it in CI in our own patch; I'll report back

[pinzonjulian]

It worked well

[marcoroth]

Thanks @pinzonjulian for opening this!

Once we have this merged here, I'd also love to bring over the same document/test to the Herb test suite, just to make sure we also handle that correctly in Herb itself and "lock in" the behavior using a snapshot test.