Custom tags are printed on newline instead of after the key

[avisprince]

Describe the bug
I am creating custom tags that handles non scalar values. The way the yaml is formatted though is unexpected. See below:

Expected:

foo:
  bar: !append
    - hello
    - world

Actual

foo:
  bar:
    !append
    - hello
    - world

To Reproduce
Here is my code:

const APPEND_PATCH = {
  tag: '!append',  
  identify: value => value.tag === '!append',
  createNode: (_, item) => {
    const x = new yaml.YAMLSeq();
    x.tag = '!append';
    item.value.forEach(v => x.add(v));
    return x;
  },
}

class AppendPatch {
  tag = '!append';
  value;

  constructor(val) {
    this.value = val;
  }
}

const TEST = {
  foo: {
    bar: new AppendPatch(['hello', 'world'])
  }
}

const result = yaml.stringify(struct, {
    nullStr: '~',
    customTags: [APPEND_PATCH],
  });

console.log(result);

[eemeli]

A PR fixing this to the "expected" result would be most welcome.

[smith-xyz]

ahh yeah, noticed that too. Just to ask, is the new line actually a technical spec for yaml? Wondering what the convention is there, if any.

Without using custom tags at all:

import YAML from "yaml";

const yaml = `
--- 
:custom: !seq:Custom 
  - :cnt: 1
  - :cnt: 2
`;

const result = YAML.parseDocument(yaml);

console.log(result.toJS());
// { ':custom': [ { ':cnt': 1 }, { ':cnt': 2 } ] }

console.log(result.warnings);
// Unresolved tag: !seq:Custom at line 3, column 10

console.log(result.toString()); 
// ---
// :custom:
//   !seq:Custom
//   - :cnt: 1
//   - :cnt: 2

[eemeli]

Just to ask, is the new line actually a technical spec for yaml? Wondering what the convention is there, if any.

Could you rephrase this question? In general, newlines may be significant in YAML, but specifically the value of a mapping pair may extend from the same line as the : to subsequent lines, as long as the content on those lines is more indented than the parent.

There's no official convention for how a value like this ought to be serialised, though, so it's really whatever feels most appropriate for each implementation.