Keep empty arrays & objects on same line

[movingobjects]

I'd love to have (an option for?) empty arrays/objects be outputted on the same line.

For example, given the data:

const data = { a: [], b: {} };

Running stringify(data, { space: 2 }) returns:

{
  "a": [
  ],
  "b": {
  }
}

Whereas JSON.stringify(data, null, 2) returns:

{
  "a": [],
  "b": {}
}

I find the latter, with the empty arrays/objects on the same line, much easier to read.

It also seems to matches how most other JSON tools handle empty arrays/objects (e.g., VSCode's Format Document command, https://jsonformatter.org/, https://www.jsonformatter.io/, and others).

Thanks!

[ljharb]

That seems reasonable, and I agree it's easier to read. A new boolean option, say, collapseEmpty, should cover it.

[devon-wolf]

Hi! Thanks for all your work on this! I'm looking to pick up this issue and wanted to clarify something.

In the space.js tests, there's a test to check that its behavior is the same as JSON.stringify (minus, of course, the purposeful additions) - adding a test for these empty cases will clarify that these newlines are a divergence from the base behavior:

test('space parameter (empty arrays and objects same as native)', function (t) {
	t.plan(1);
	// for this test, properties need to be in alphabetical order
	var obj = { emptyArr: [], emptyObj: {} };
	t.equal(
		stringify(obj, { space: '  ' }),
		JSON.stringify(obj, null, '  ')
	);
});

results in:

# space parameter (empty arrays and objects same as native)
not ok 20 should be strictly equal
  ---
    operator: equal
    expected: |-
      '{\n  "emptyArr": [],\n  "emptyObj": {}\n}'
    actual: |-
      '{\n  "emptyArr": [\n  ],\n  "emptyObj": {\n  }\n}'

Rather than a boolean option to specify that this extra newline should not be added, I would be inclined to handle these cases in space itself. Since the tests suggest the shape should align with JSON.stringify, this feels like an edge-case bug to me rather than a configuration choice.

I'm guessing your thought behind the collapseEmpty option is that changing this behavior within space would be a breaking change? That makes sense, especially since the whole point here is to produce JSON output with consistent hashes, so I'm starting work with the assumption that this option will be needed, but if you think it won't be disruptive for future releases to change the space behavior under the hood for all cases I'll switch to that approach.

[ljharb]

Yes, that's exactly the thought.