New rule: `svelte/prefer-derived-over-derived-by`

[baseballyama]

Motivation

From a consistency perspective, this rule reports unnecessary usage of $derived.by. There is no performance difference. It purely enforces a consistent coding style. Even if included in recommended config, a warning level should be sufficient.

Description

This rule reports unnecessary usage of $derived.by. It also provides a fixer to automatically convert $derived.by to $derived.

Examples

<script>
// ✓ GOOD
const foo = $derived(a.b);

// ✗ BAD
const bar = $derived.by(() => a.b);
</script>

Additional comments

No response