Line break normalization

Hi,

Recently, I implemented a YAML parser, which is going to be 
mainly used in Microsoft Windows environments, where the 
system default line breaks are "\r\n" instead of "\n". 

During that, I had to think about the way to store multi-line 
scalar nodes in YAML documents.

At first, I thought the best way is to use the literal style: 

%YAML 1.2
---
|2+
  abc
    def
  ghi
...

But I found a description that this document must always be 
parsed as "abc\n  def\nghi\n" and not as "abc\r\n  def\r\nghi\r\n".

> Section 5.4. Line Break Characters
>
> Line breaks inside scalar content  must be normalized by the 
> YAML processor. Each such line break must be parsed into a 
> single line feed character. The original line break format 
> is a presentation detail  and must not be used to convey 
> content information. 

I understood the spec wanted to have the meaning of a YAML 
document be independent of the environments in which it is
interpreted.

Then, the only way I found to express "abc\r\n  def\r\nghi\r\n" 
in YAML was:

%YAML 1.2
---
"abc\r\n\
\  def\r\n\
ghi\r\n"
...

This is unacceptably ugly. 

But I'm afraid there is no better way to do it with the current 
specification. Is there any?


If we discuss some improvement of the specification to solve this 
problem, I suggest two solutions.


1. Declaring a YAML processor should normalize line breaks to the 
system default line breaks, instead of a single line feed "\n".

This causes the character stream expression of an unescaped text 
vary depending on the environment where it is interpreted.

At first glance, this is unacceptable. 

But, we should remember that, a YAML processor is allowed to or almost 
required to normalize the character encoding of text data in a YAML 
document to the system default, "because the character encoding is a 
presentation detail and must not be used to convey content information.
(5.2. Character Encodings)" 

If line break format is also a presentation detail, the specification 
should require line break normalization not always to a single line feed 
but to the system default.


2. Introducing a new directive, something like %LINEBREAK.
This will preserves the character stream expression of text data without 
explicitely escaping line breaks.

%YAML 1.2
%LINEBREAK "\r\n"
---
|2+
  abc
    def
  ghi
...


I vote to the first option because it is consistent to the way of dealing 
with the character encoding, fmm, and %LINEBREAK directive is not good 
looking for me.


Best,
Osamu Takeuchi

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