Automatic folding on double quotes with large key produces incorrect output

[diogotcorreia]

When both the key and the content are big, and it needs to be double-quoted (e.g. because of the & character), it doesn't correctly stringify the object.

Code:

const yaml = require("yaml");

const input = {
  testgljrisgjsrligjsrligsjrglisrjgrligjsligrjglisjgrlijgsrilgsejrfiwlahflirgjaelfjafil:
    "&cLorem ipsum dolor sit amet, consectetur adipiscing elit. Sed sed nibh ac metus elementum venenatis eu vitae diam. Etiam tristique suscipit mauris. Donec pulvinar sed nunc a gravida. Morbi nulla lacus, gravida eu elementum id, ultricies nec ipsum. Cras bibendum tellus ut mollis malesuada. Maecenas eleifend felis at fermentum hendrerit. Nulla porta vitae erat eget faucibus. Sed egestas viverra magna ac vulputate. Suspendisse vel posuere mauris, accumsan dapibus libero. Curabitur bibendum tellus in ex ultricies, quis tempus magna luctus. Maecenas maximus orci est, id fringilla lorem gravida sit amet. Pellentesque a rutrum lorem. Vestibulum ante ipsum primis in faucibus orci.",
};

console.log(yaml.stringify(input));

Output:

testgljrisgjsrligjsrligsjrglisrjgrligjsligrjglisjgrlijgsrilgsejrfiwlahflirgjaelfjafil: "&cLorem ipsum dolor sit amet, consectetur adipiscing elit. Sed sed nibh ac metus elementum 
venenatis eu vitae diam. Etiam tristique suscipit mauris. Donec pulvinar sed nunc a gravida. Morbi nulla lacus, gravida eu elementum id, ultricies nec ipsum. Cras bibendum tellus 
ut mollis malesuada. Maecenas eleifend felis at fermentum hendrerit. Nulla porta vitae erat eget faucibus. Sed egestas viverra magna ac vulputate. Suspendisse vel posuere mauris, 
accumsan dapibus libero. Curabitur bibendum tellus in ex ultricies, quis tempus magna luctus. Maecenas maximus orci est, id fringilla lorem gravida sit amet. Pellentesque a rutrum lorem. Vestibulum ante ipsum primis in faucibus orciundefined\

  metus elementum venenatis eu vitae diam. Etiam tristique suscipit mauris.
  Donec pulvinar sed nunc a gravida. Morbi nulla lacus, gravida eu elementum id,
  ultricies nec ipsum. Cras bibendum tellus ut mollis malesuada. Maecenas
  eleifend felis at fermentum hendrerit. Nulla porta vitae erat eget faucibus.
  Sed egestas viverra magna ac vulputate. Suspendisse vel posuere mauris,
  accumsan dapibus libero. Curabitur bibendum tellus in ex ultricies, quis
  tempus magna luctus. Maecenas maximus orci est, id fringilla lorem gravida sit
  amet. Pellentesque a rutrum lorem. Vestibulum ante ipsum primis in faucibus
  orci."

Notice the undefined\ that appears and the duplicated content.

[dota17]

yaml/src/stringify/foldFlowLines.js

Line 49 in 3b807a1

let end =

This is a bug. When the length of the key is greater than 80, the end will be a negative number and then causes subsequent output problems. I'll try to fix it.

[eemeli]

@dota17 Are you still working on this? I'd like to put together a new release soon that should include a fix for this.

[eemeli]

I ended up solving this myself. The scalarOptions.str.fold.minContentWidth option is now also used as a requirement for the width of the first line when folding long strings. In addition to fixing this actual error, it should allow for slightly prettier output.

The issue was indeed a negative fold position as @dota17 identified, but not directly due to end being negative. Instead it's because of this adjustment:

yaml/src/stringify/foldFlowLines.js

Lines 106 to 107 in 9805351

	// i - 2 accounts for not-dropped last char + newline-escaping \
	folds.push(i - 2)

For very high indentAtStart values, end is low enough for i here to be less than 2, which becomes a problem when the fold is later used to initialise the first line of input:

yaml/src/stringify/foldFlowLines.js

Line 121 in 9805351

let res = text.slice(0, folds[0])

In this case that should be an empty string, but it actually contains most of the original string.

[dota17]

Good! I am on a long vacation last week and sorry for delay.