no-dupe-else-if-blocks.md

Pattern: Duplicate condition in {#if}/{:else if} chain

Issue: -

Description

This rule disallows duplicate conditions in the same {#if} / {:else if} chain.

<script>
  /* eslint svelte/no-dupe-else-if-blocks: "error" */
</script>

<!-- ✓ GOOD -->
{#if a}
  <div>foo</div>
{:else if b}
  <div>bar</div>
{:else if c}
  <div>baz</div>
{/if}

<!-- ✗ BAD -->
{#if a}
  <div>foo</div>
{:else if b}
  <div>bar</div>
{:else if b}
  <div>baz</div>
{/if}

{#if a}
  <div>foo</div>
{:else if b}
  <div>bar</div>
{:else}
  baz
  {#if b}
    <div>qux</div>
  {/if}
{/if}

This rule can also detect some cases where the conditions are not identical, but the branch can never execute due to the logic of || and && operators.

<script>
  /* eslint svelte/no-dupe-else-if-blocks: "error" */
</script>

<!-- ✗ BAD -->
{#if a || b}
  1
{:else if a}
  2
{/if}

{#if a}
  1
{:else if b}
  2
{:else if a || b}
  3
{/if}

{#if a}
  1
{:else if a && b}
  2
{/if}

{#if a && b}
  1
{:else if a && b && c}
  2
{/if}

{#if a || b}
  1
{:else if b && c}
  2
{/if}

{#if a}
  1
{:else if b && c}
  2
{:else if d && ((c && e && b) || a)}
  3
{/if}

🔧 Options

Nothing.

👫 Related Rules

• no-dupe-else-if

🚀 Version

This rule was introduced in eslint-plugin-svelte v0.0.1

🔍 Implementation

• Rule source
• Test source