`#magic___^_^___line` when `retain_line_breaks: true` about yamlfmt HOT 2 CLOSED

You are indeed correct! With scan_folded_as_literal: true in my real example seems to give the correct output. Thanks a lot for the quick help!

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Thanks for making an issue and the kind words!

This appears to be a strange edge case of scanning folded block scalars, something that's been a hassle. There's two bits of weirdness, one of which yamlfmt has a workaround for, and one that probably needs investigation in the library.

The one with a workaround is that the underlying yaml library cuts out lines for folded block scalars. This actually kind of makes sense, since that's a correct interpretation of folded block scalars from the spec, however it's really uncool for a tool like this where we want to maintain that form. For that, I've implemented a feature in the yaml library that forces re-encoding folded block scalars to retain the line breaks. I added a boolean option in the formatter config called scan_folded_as_literal to enable this. See the config docs for a bit more info there. With scan_folded_as_literal enabled, the first example in the issue remains the same after format.

The second weirdness is something I actually discovered just now while reproducing the issue. If a line in a folded block scalar ends with space characters, the encoder throws a fit and dumps the raw string value instead of producing a folded block scalar as intended. If whitespace is left at the end of a folded block scalar, you get output like this:

Foobar:
  baz: "Lorem Ipsum is simply dummy text of the printing_and_typesetting industry.
    \n#magic___^_^___line\n"
Foobaz:
  baz: "foobar"

This is a really annoying consequence, and I'll start tackling it soon.

That being said, hopefully scan_folded_as_literal will work for your issue! If it does, I will close this issue; I'll be starting the new investigation for folded block scalar lines ending with whitespace in a new issue dedicated to it.

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