Limits

Svelte Scoped Props is an experiment. These boundaries are intentional for the alpha.

Not a Svelte core feature

The package is a preprocessor that runs before Svelte parses the component. Native compiler support would have access to Svelte’s already-computed CSS scope hash and would not need to mirror private hash behavior.

Private hash mirror

Svelte does not currently export its default cssHash helper as a public API. This package mirrors that implementation. If Svelte changes the private default hash, projects should update this package or pass their own cssHash.

scopedProps({
    cssHash: ({ css, filename, hash }) => `svelte-${hash(filename ?? css)}`
})

scopedProps({
    cssHash: ({ css, filename, hash }) => `svelte-${hash(filename ?? css)}`
})

No child type graph

The preprocessor does not inspect the imported child component or its TypeScript prop types. scoped:class is an explicit usage-site decision by the parent.

That keeps the transform small, but it also means scoped: cannot automatically know which child props are ClassValue props.

Component tags only

Only uppercase and dotted component tags are supported.

<Child scoped:class="parent-owned" />
<motion.div scoped:class="parent-owned" />

<Child scoped:class="parent-owned" />
<motion.div scoped:class="parent-owned" />

Native elements are rejected because normal Svelte class behavior already works there.

Scope before spread

Object spreads cannot express Svelte directive syntax. Use scoped: before props are collected into an object, then forward the transformed prop normally.

Marker snippet

By default, the transform adds an uncalled snippet marker so Svelte keeps the parent CSS selector alive during CSS analysis. The marker does not render, but it can leave a small unused function in compiled output.

scopedProps({ marker: false })

scopedProps({ marker: false })

Only disable the marker when you are running transform-level tests and are not asking Svelte to compile scoped CSS.

CSS scanning

The alpha scanner is intentionally small. It handles normal class selectors, but it is not a full CSS parser. Escaped or highly unusual selector forms may need more work.