Recast is adding extra newlines in ObjectExpressions

[kumarharsh]

Refer to the following fiddle: http://astexplorer.net/#/27xKOBJJGN

When I have an object with a structure such as this:

const styles = {
  base: {
    height: '100%',
  },
  ribbon: {
    backgroundColor: 'black',
  },
};

and I do anything with the body of the ObjectExpression like this:

export default function(file, api) {
  const j = api.jscodeshift;
  window.j = j;
  const { statement, statements } = j.template;
  return j(file.source)
    .find(j.VariableDeclarator)
    .replaceWith(p => {
        p.node.init = j.objectExpression(p.node.init.properties);
        return p.node;
    })
    .toSource();
};

then the following output is gotten:

const styles = {
  base: {
    height: '100%',
  },

  ribbon: {
    backgroundColor: 'black',
  }
};

see that extra newline after base and before ribbon. These lines are added after every property, which is adding unnecessary changes to my codebase. Is there a way to suppress that? or is that a bug?

[kumarharsh]

Thinking about this a little, I'm inclined to believe that this is also related to #240. Essentially, the printer is forcefully adding one extra newline after each property in an objectExpression. So, if there is none, then there will be one. If there's one, then there will be two. But if there's two or more, then nothing happens.

[kumarharsh]

This comes from

recast/lib/printer.js

Lines 624 to 627 in 827ae9f

	// Add an extra line break if the previous object property
	// had a multi-line value.
	parts.push(separator + (multiLine ? "\n\n" : "\n"));
	allowBreak = !multiLine;

From what I've seen, the practice of writing code as I've given in the first code snippet above is quite common and, at risk of sounding too narrow-minded, no one writes an extra newline in their code separating the properties of an objectExpression, not even Facebook.

[petrfelzmann]

#353

[pksjce]

+1
I faced the same issue! My PR linked above is not an informed fix but it fixes this particular issue while not breaking any test cases. I also wrote a failing test case for this and made it oss as per of that PR

[nickretallack]

I found a ton of examples of cases where this happens. I originally filed a bug here: zxbodya/flowts#11

It seems any property that spans multiple lines causes extra newlines, even if it's just because it has a comment.

[danielo515]

It is happening something similar to me. This code, for example:

  const shortProperty = (j, identifier) => {
    return { ...j.objectProperty(identifier, identifier), shorthand: true };
  };


export default function (file, api) {
  const j = api.jscodeshift;

  const call = j.variableDeclaration("const", [
      j.variableDeclarator(
        j.objectPattern([shortProperty(j,j.identifier("__"))]),
        j.callExpression(j.identifier("usePulyglot"), [
          j.identifier("phrases")
        ])
      )
    ])
  
    return j(call).toSource();
}

Produces this output:

const {
  __
} = usePulyglot(phrases); = 99

But I expected this instead:

const { __ } = usePulyglot(phrases); = 99

Here is a playground:

https://astexplorer.net/#/gist/eeee224efd6c389deb8a82a338e4fbe7/latest

[villesau]

Made a fix for this: #1262

[yhancsx]

I have similar problem

https://astexplorer.net/#/gist/eeee224efd6c389deb8a82a338e4fbe7/af669315e6eead72e30a403b05298edd685fd864