fix: uneval grows sparse arrays by one slot when first hole is past index 0

[spokodev]

What

uneval grows a sparse array by one slot when its first hole is not at index 0:

import { uneval } from 'devalue';

uneval([1, , 3]);   // '[1,,,3]'  → evaluates to [1, <2 empty>, 3], length 4
uneval([1, , ]);    // '[1,,,]'   → length 3
uneval([1, , , 4]); // '[1,,,,4]' → length 5

stringify/parse round-trips these correctly — only uneval is affected. ([, 'a'], where the first hole is at index 0, was already correct, which is why this slipped through.)

Why

In the array-literal branch, a comma is written at the top of every iteration (if (i > 0) result += ','). When the first hole is reached, the code set has_holes = true and then did i -= 1 to "re-process this index as a hole" — but the re-processed iteration writes a second comma for the same slot, so each such array gains one element.

Fix

The comma written at the top of the iteration already represents the hole, so the i -= 1 re-processing is unnecessary (and is what caused the extra comma). Removing it makes every case round-trip:

input	before	after
[1, , 3]	[1,,,3] (len 4)	[1,,3] (len 3)
[1, , ]	[1,,,] (len 3)	[1,,] (len 2)
[1, , , 4]	[1,,,,4] (len 5)	[1,,,4] (len 4)
[, 'a', , 'b']	[,"a",,"b"] (unchanged)	[,"a",,"b"]

The Object.assign path for very sparse arrays returns earlier and is unaffected.

Tests

Added a round-trip test for sparse arrays whose first hole is not at index 0 (red before the change, green after). Full npm test passes (659).

[changeset-bot]

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Latest commit: fcddf82

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
devalue	Patch

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