Awkward formatting of elisions in array assignment patterns

Prettier 1.19.1 Playground link

--parser babel

Input:

switch (LTocurrenceCount) {
        case 1: 
          itemToAddToFinalResult = item;
          break;
        case 2: {
          const [, secondDuplicateIdx] = mappingWithPossibleDoubledInputs
            .map((item1, idx1) => (item1.labelText === labelText ? idx1 : undefined))
            .filter(Boolean);
          if (idx === secondDuplicateIdx) {
            itemToAddToFinalResult = give_special_treatment(item);
          } else itemToAddToFinalResult = item;
          break;
        }
        default:
          console.error("more than 2 occurences!");
      }

Output:

switch (LTocurrenceCount) {
  case 1:
    itemToAddToFinalResult = item;
    break;
  case 2: {
    const [
      ,
      secondDuplicateIdx
    ] = mappingWithPossibleDoubledInputs
      .map((item1, idx1) => (item1.labelText === labelText ? idx1 : undefined))
      .filter(Boolean);
    if (idx === secondDuplicateIdx) {
      itemToAddToFinalResult = give_special_treatment(item);
    } else itemToAddToFinalResult = item;
    break;
  }
  default:
    console.error("more than 2 occurences!");
}

Expected behavior: I would expect the const [, secondDuplicateIdx] part not to break into muplitple lines.

[fisker]

Array with holes

Prettier 1.19.1 Playground link

--parser babel

Input:

const arrayWithManyHoles = [
  first, , , , , , , , , , , , , , , , , , , , , , , , ,
  last
]

Output:

const arrayWithManyHoles = [
  first,
  ,
  ,
  ,
  ,
  ,
  ,
  ,
  ,
  ,
  ,
  ,
  ,
  ,
  ,
  ,
  ,
  ,
  ,
  ,
  ,
  ,
  ,
  ,
  ,
  last
];

Expected:

Maybe keep holes after the first one, like input.

[thorn0]

@brodybits Please add Expected because to me it’s not clear what’s wrong with the current output.