Change @shikijs/transformers range by + 1

[richardgill]

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• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.

Describe the bug

// [!code highlight:2]
console.log('highlighted')
console.log('not highlighted')

Ranges on transformations include the current line, to me this was very uninuitive.

Instead it could be:

// [!code highlight:2]
console.log('highlighted')
console.log('highlighted')

Currently: // [!code highlight] is effectively // [!code highlight:1]
Becomes: // [!code highlight:0]

I guess this is a breaking change, and it is slightly arbitary - so no worries if you disagree :)

Reproduction

Included in comment

Contributes

• I am willing to submit a PR to fix this issue
• I am willing to submit a PR with failing tests

[fuma-nama]

Noticed this problem too, it's because the notation highlighter was initially designed as:

console.log('highlighted') // [!code highlight:2]
console.log('not highlighted')

See https://shiki.style/packages/transformers#transformernotationhighlight

So when the comment was added to an empty line, it still start counting from the current line.
The exact problem is that we need to consider the case of empty lines, we still need the approval from maintainers since it should be a breaking change (impacts normal usages).

[antfu]

I am up to it, feel free to bring up a PR and then we could discuss how we enroll it with the minimal impact to the existing users