Add support for "value associated with the merge key is a sequence"

[jjkavalam]

Describe the bug

If the value associated with the merge key is a sequence (rather than a single mapping node), following error is thrown when attempting doc.toJS() doc.toJSON():

Merge sources must be maps or map aliases

To Reproduce
Steps to reproduce the behaviour.

const YAML = require("yaml");

const sourceError = `
- citrus: &citrus
  - { lemon: yellow }
  - { tangerine: orange }

- fruit-colors:
    <<: *citrus
`;

const sourceNoError = `
- citrus: &citrus
    lemon: yellow
    tangerine: orange

- fruit-colors:
    <<: *citrus
`;

function parseAndConvert(source) {
  console.log("parseAndCovert: >> %s <<", JSON.stringify(source));
  const doc = YAML.parseDocument(source, { merge: true });
  console.log(doc.toString());
  console.log(doc.toJS());
}

parseAndConvert(sourceNoError);
parseAndConvert(sourceError);

parseAndCovert: >> "\n- citrus: &citrus\n    lemon: yellow\n    tangerine: orange\n\n- fruit-colors:\n    <<: *citrus\n" <<
- citrus:
    &citrus
    lemon: yellow
    tangerine: orange

- fruit-colors:
    <<: *citrus

[
  { citrus: { lemon: 'yellow', tangerine: 'orange' } },
  { 'fruit-colors': { lemon: 'yellow', tangerine: 'orange' } }
]
parseAndCovert: >> "\n- citrus: &citrus\n  - { lemon: yellow }\n  - { tangerine: orange }\n\n- fruit-colors:\n    <<: *citrus\n" <<
- citrus:
    &citrus
    - { lemon: yellow }
    - { tangerine: orange }

- fruit-colors:
    <<: *citrus

node_modules/yaml/dist/nodes/addPairToJSMap.js:59
        throw new Error('Merge sources must be maps or map aliases');
        ^

Error: Merge sources must be maps or map aliases
    at mergeToJSMap 

Expected behaviour

When the value associated with the merge key is a sequence, the elements of the sequence must be merged in one by one.

The expected behaviour is described here: https://github.com/eemeli/yaml/blob/master/src/nodes/addPairToJSMap.ts#L54

Versions (please complete the following information):

• Environment: Node.js v14.14.0
• yaml: 1.10.0, 2.0.0-8

[sourcevault]

what is the solution ?

js = yaml.parse(doc.toString(),{merge:true})

js1 = doc.toJS {merge:true}

I am having to use doc.toString(), what is the direct way to do on doc ?

[eemeli]

@sourcevault Please open a new discussion for your query, including a complete example of what you're looking to do.

[sourcevault]

Hi @eemeli

I found the solution.

doc.setSchema('1.1')
js = doc.toJS()

not sure if this is the expected pattern or workaround.