Multiline strings are not emitted in the literal/folded style

[ltrzesniewski]

I noticed that SharpYaml doesn't emit multiline strings in the literal or folded style.

At first, I thought I missed a setting, but after digging a bit in the code this seems unintentional:

First, here's a repro to show what I mean:

using System;
using System.Collections.Generic;

namespace ConsoleApp;

public static class Program
{
    public static void Main()
    {
        var data = new Dictionary<string, string> { { "Key", "Foo\r\nBar" } };

        Console.WriteLine(new YamlDotNet.Serialization.SerializerBuilder().Build().Serialize(data));
        Console.WriteLine("---");
        Console.WriteLine(new SharpYaml.Serialization.Serializer(new() { EmitTags = false }).Serialize(data));
    }
}

Output:

Key: >-
  Foo

  Bar

---
Key: "Foo\r\nBar"

Bonus points if SharpYaml could use literal style by default instead: 🙂

Key: |-
  Foo
  Bar

I suppose you may want to add a setting to tell if the serialized value needs to be round-trippable regarding the \r character, as YAML would normalize the line break to \n on deserialization.

---

Here's what happens:

The following code turns ScalarStyle.Folded into ScalarStyle.DoubleQuoted when isBlockAllowed is false:

SharpYaml/src/SharpYaml/Emitter.cs

Lines 1524 to 1530 in 3105d16

	if (style == ScalarStyle.Literal || style == ScalarStyle.Folded)
	{
	if (!scalarData.isBlockAllowed || flowLevel != 0 || isSimpleKeyContext)
	{
	style = ScalarStyle.DoubleQuoted;
	}
	}

Here, isBlockAllowed is set to false when special_characters is true:

SharpYaml/src/SharpYaml/Emitter.cs

Lines 549 to 555 in 3105d16

	if (space_break || special_characters)
	{
	scalarData.isFlowPlainAllowed = false;
	scalarData.isBlockPlainAllowed = false;
	scalarData.isSingleQuotedAllowed = false;
	scalarData.isBlockAllowed = false;
	}

And here, special_characters is set to true when !buffer.IsPrintable():

SharpYaml/src/SharpYaml/Emitter.cs

Lines 462 to 465 in 3105d16

	if (!special_characters && !buffer.IsPrintable())
	{
	special_characters = true;
	}

CR and LF are not considered printable:

SharpYaml/src/SharpYaml/Emitter.cs

Lines 1110 to 1117 in 3105d16

	internal static bool IsPrintable(char character)
	{
	return
	(character >= '\x20' && character <= '\x7E') ||
	character == '\x85' ||
	(character >= '\xA0' && character <= '\xD7FF') ||
	(character >= '\xE000' && character <= '\xFFFD');
	}

I'm not sure at which point a change would need to be applied. YamlDotNet has a different logic for setting isBlockAllowed to false.