perf(utils): improve performance of numberToPos

[yuzheng14]

Description

This PR optimizes the numberToPos function, achieving 1.66x-2.27x performance improvement across different JavaScript runtimes. The refactored implementation also provides clearer and more maintainable code.

Benchmarks

The code of benchmarks is shown at Stackblitz.

Performance was measured using a 9,179-character test file across multiple runtimes locally.

Behavior Changes

The current implementation return positions like { line: /* previous line */, column: /* line length including newline */ }. The new implementation consistently return the start position of the next line like { line: /* exact the line */, column: 0 }, which better aligns with the 0-based column described in the Pos type comments.

vite/packages/vite/src/node/utils.ts

Lines 471 to 476 in 657c2fa

	type Pos = {
	/** 1-based */
	line: number
	/** 0-based */
	column: number
	}

[yuzheng14]

I noticed an inconsistency in the previous test snapshot: when receiving an offset of 8, it returns { line: 1, column: 9 } which appears incorrect.

[sapphi-red]

Thanks! The change looks good to me.
Would you add some tests for numberToPos below here so that we can catch the bug you found more easily?

vite/packages/vite/src/node/__tests__/utils.spec.ts

Lines 229 to 246 in 657c2fa

	describe('posToNumber', () => {
	test('simple', () => {
	const actual = posToNumber('a\nb', { line: 2, column: 0 })
	expect(actual).toBe(2)
	})
	test('pass though pos', () => {
	const actual = posToNumber('a\nb', 2)
	expect(actual).toBe(2)
	})
	test('empty line', () => {
	const actual = posToNumber('a\n\nb', { line: 3, column: 0 })
	expect(actual).toBe(3)
	})
	test('out of range', () => {
	const actual = posToNumber('a\nb', { line: 4, column: 0 })
	expect(actual).toBe(4)
	})
	})

[bluwy]

Nice! It looks more readable too