allow passing snippets rendered as slots

packages/svelte/src/compiler/phases/3-transform/client/visitors/template.js

@@ -789,6 +789,8 @@ function serialize_inline_component(node, component_name, context) {
 
 	/** @type {import('estree').Statement[]} */
 	const snippet_declarations = [];
+	/** @type {import('estree').Property[]} */
+	const serialized_slots = [];
 
 	// Group children by slot
 	for (const child of node.fragment.nodes) {
@@ -802,6 +804,8 @@ function serialize_inline_component(node, component_name, context) {
 			});
 
 			push_prop(b.prop('init', child.expression, child.expression));
+			// Back/forward compatibility: allows people to pass snippets when component still uses slots
+			serialized_slots.push(b.init(child.expression.name, b.true));
 
 			continue;
 		}
@@ -825,8 +829,6 @@ function serialize_inline_component(node, component_name, context) {
 	}
 
 	// Serialize each slot
-	/** @type {import('estree').Property[]} */
-	const serialized_slots = [];
 	for (const slot_name of Object.keys(children)) {
 		const body = create_block(node, `${node.name}_${slot_name}`, children[slot_name], context);
 		if (body.length === 0) continue;
@@ -3070,11 +3072,14 @@ export const template_visitors = {
 						b.block(create_block(node, 'fallback', node.fragment.nodes, context))
 					);
 
-		const expression = is_default
+		const slot = b.call(
-			? b.call('$.default_slot', b.id('$$props'))
+			'$.slot',
-			: b.member(b.member(b.id('$$props'), b.id('$$slots')), name, true, true);
+			context.state.node,
-
+			b.id('$$props'),
-		const slot = b.call('$.slot', context.state.node, expression, props_expression, fallback);
+			name,
+			props_expression,
+			fallback
+		);
 		context.state.init.push(b.stmt(slot));
 	},
 	SvelteHead(node, context) {

packages/svelte/src/compiler/phases/3-transform/server/transform-server.js

@@ -1037,6 +1037,8 @@ function serialize_inline_component(node, component_name, context) {
 
 	/** @type {import('estree').Statement[]} */
 	const snippet_declarations = [];
+	/** @type {import('estree').Property[]} */
+	const serialized_slots = [];
 
 	// Group children by slot
 	for (const child of node.fragment.nodes) {
@@ -1050,6 +1052,8 @@ function serialize_inline_component(node, component_name, context) {
 			});
 
 			push_prop(b.prop('init', child.expression, child.expression));
+			// Back/forward compatibility: allows people to pass snippets when component still uses slots
+			serialized_slots.push(b.init(child.expression.name, b.true));
 
 			continue;
 		}
@@ -1071,9 +1075,6 @@ function serialize_inline_component(node, component_name, context) {
 	}
 
 	// Serialize each slot
-	/** @type {import('estree').Property[]} */
-	const serialized_slots = [];
-
 	for (const slot_name of Object.keys(children)) {
 		const body = create_block(node, children[slot_name], context);
 		if (body.length === 0) continue;
@@ -1750,7 +1751,7 @@ const template_visitors = {
 		const lets = [];
 
 		/** @type {import('estree').Expression} */
-		let expression = b.call('$.default_slot', b.id('$$props'));
+		let slot_name = b.literal('default');
 
 		for (const attribute of node.attributes) {
 			if (attribute.type === 'SpreadAttribute') {
@@ -1758,7 +1759,7 @@ const template_visitors = {
 			} else if (attribute.type === 'Attribute') {
 				const value = serialize_attribute_value(attribute.value, context, false, true);
 				if (attribute.name === 'name') {
-					expression = b.member(b.member_id('$$props.$$slots'), value, true, true);
+					slot_name = value;
 				} else if (attribute.name !== 'slot') {
 					if (attribute.metadata.dynamic) {
 						props.push(b.get(attribute.name, [b.return(value)]));
@@ -1782,7 +1783,14 @@ const template_visitors = {
 			node.fragment.nodes.length === 0
 				? b.literal(null)
 				: b.thunk(b.block(create_block(node, node.fragment.nodes, context)));
-		const slot = b.call('$.slot', b.id('$$payload'), expression, props_expression, fallback);
+		const slot = b.call(
+			'$.slot',
+			b.id('$$payload'),
+			b.id('$$props'),
+			slot_name,
+			props_expression,
+			fallback
+		);
 
 		state.template.push(t_statement(b.stmt(slot)));
 		state.template.push(block_close);

packages/svelte/src/internal/client/dom/legacy/misc.js

@@ -66,15 +66,3 @@ export function update_legacy_props($$new_props) {
 		}
 	}
 }
-
-/**
- * @param {Record<string, any>} $$props
- */
-export function default_slot($$props) {
-	var children = $$props.$$slots?.default;
-	if (children === true) {
-		return $$props.children;
-	} else {
-		return children;
-	}
-}

packages/svelte/src/internal/client/index.js

@@ -72,8 +72,7 @@ export {
 	add_legacy_event_listener,
 	bubble_event,
 	reactive_import,
-	update_legacy_props,
+	update_legacy_props
-	default_slot
 } from './dom/legacy/misc.js';
 export {
 	append,

packages/svelte/src/internal/client/render.js

@@ -63,11 +63,21 @@ export function set_text(dom, value) {
 
 /**
  * @param {Comment} anchor
- * @param {void | ((anchor: Comment, slot_props: Record<string, unknown>) => void)} slot_fn
+ * @param {Record<string, any>} $$props
+ * @param {string} slot_name
  * @param {Record<string, unknown>} slot_props
  * @param {null | ((anchor: Comment) => void)} fallback_fn
  */
-export function slot(anchor, slot_fn, slot_props, fallback_fn) {
+export function slot(anchor, $$props, slot_name, slot_props, fallback_fn) {
+	var slot_fn = $$props.$$slots?.[slot_name];
+	if (slot_fn === true) {
+		if (slot_name === 'default') {
+			slot_fn = $$props.children;
+		} else {
+			slot_fn = $$props[slot_name];
+		}
+	}
+
 	if (slot_fn === undefined) {
 		if (fallback_fn !== null) {
 			fallback_fn(anchor);

packages/svelte/src/internal/server/index.js

@@ -499,12 +499,22 @@ export async function value_or_fallback_async(value, fallback) {
 
 /**
  * @param {Payload} payload
- * @param {void | ((payload: Payload, props: Record<string, unknown>) => void)} slot_fn
+ * @param {Record<string, any>} $$props
+ * @param {string} slot_name
  * @param {Record<string, unknown>} slot_props
  * @param {null | (() => void)} fallback_fn
  * @returns {void}
  */
-export function slot(payload, slot_fn, slot_props, fallback_fn) {
+export function slot(payload, $$props, slot_name, slot_props, fallback_fn) {
+	var slot_fn = $$props.$$slots?.[slot_name];
+	if (slot_fn === true) {
+		if (slot_name === 'default') {
+			slot_fn = $$props.children;
+		} else {
+			slot_fn = $$props[slot_name];
+		}
+	}
+
 	if (slot_fn === undefined) {
 		if (fallback_fn !== null) {
 			fallback_fn();
@@ -631,5 +641,3 @@ export {
 } from '../shared/validate.js';
 
 export { escape_html as escape };
-
-export { default_slot } from '../client/dom/legacy/misc.js';

packages/svelte/tests/runtime-runes/samples/snippet-slot-interop/Child.svelte

@@ -0,0 +1,2 @@
+<p><slot /></p>
+<p><slot name="named" /></p>

packages/svelte/tests/runtime-runes/samples/snippet-slot-interop/_config.js

@@ -0,0 +1,5 @@
+import { test } from '../../test';
+
+export default test({
+	html: `<p>Default</p> <p>Named</p>`
+});

packages/svelte/tests/runtime-runes/samples/snippet-slot-interop/main.svelte

@@ -0,0 +1,10 @@
+<script>
+	import Child from './Child.svelte';
+</script>
+
+<Child>
+	Default
+	{#snippet named()}
+		Named 
+	{/snippet}
+</Child>