New rule: require-slot-types

[marekdedic]

Motivation

It is possible to add types to component slots and their props:

<script lang="ts">
    interface $$Slots {
        default: { prop: boolean; };
    }
</script>

<slot prop={true} />

I would like to propose a rule to enforce these slot types.

Description

The rule should report any component that includes a <slot> and does not declare the $$Slots interface.

Examples

<!-- ✓ GOOD -->
<script>
</script>

<b>No slots here!</b>



<script>
  interface $$Slots {
    default: Record<string, never>;
  }
</script>

<slot />




<script lang="ts">
    interface $$Slots {
        default: { prop: boolean; };
    }
</script>

<slot prop={true} />


<script lang="ts">
    interface $$Slots {
        named: Record<string, never>;
    }
</script>

<slot name = "named" />

<!-- ✗ BAD -->
<script>
</script>

<slot />

Additional comments

The relevant RFC.

[ota-meshi]

Memo:
New rule should be marked as experimental until the RFC is merged.
sveltejs/rfcs#38

See also: #345 (comment)

[marekdedic]

Relevant PR: sveltejs/language-tools#1058