allow <slot> to be part of a slot

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Unreleased
 
+* Support `<slot slot="...">` ([#2079](https://github.com/sveltejs/svelte/issues/2079))
 * Add `EventSource` to known globals ([#5463](https://github.com/sveltejs/svelte/issues/5463))
 * Fix compiler exception with `~`/`+` combinators and `{...spread}` attributes ([#5465](https://github.com/sveltejs/svelte/issues/5465))
 

src/compiler/compile/render_dom/wrappers/Element/create_slot_block.ts

@@ -0,0 +1,61 @@
+import ElementWrapper from './index';
+import SlotWrapper from '../Slot';
+import Block from '../../Block';
+import { sanitize } from '../../../../utils/names';
+import InlineComponentWrapper from '../InlineComponent';
+import create_debugging_comment from '../shared/create_debugging_comment';
+import { get_slot_definition } from '../shared/get_slot_definition';
+
+export default function create_slot_block(attribute, element: ElementWrapper | SlotWrapper, block: Block) {
+	const owner = find_slot_owner(element.parent);
+
+	if (owner && owner.node.type === 'InlineComponent') {
+		const name = attribute.get_static_value() as string;
+
+		if (!((owner as unknown) as InlineComponentWrapper).slots.has(name)) {
+			const child_block = block.child({
+				comment: create_debugging_comment(element.node, element.renderer.component),
+				name: element.renderer.component.get_unique_name(
+					`create_${sanitize(name)}_slot`
+				),
+				type: 'slot'
+			});
+
+			const { scope, lets } = element.node;
+			const seen = new Set(lets.map(l => l.name.name));
+
+			((owner as unknown) as InlineComponentWrapper).node.lets.forEach(l => {
+				if (!seen.has(l.name.name)) lets.push(l);
+			});
+
+			((owner as unknown) as InlineComponentWrapper).slots.set(
+				name,
+				get_slot_definition(child_block, scope, lets)
+			);
+			element.renderer.blocks.push(child_block);
+		}
+
+		element.slot_block = ((owner as unknown) as InlineComponentWrapper).slots.get(
+			name
+		).block;
+
+		return element.slot_block;
+	}
+
+	return block;
+}
+
+function find_slot_owner(owner) {
+	while (owner) {
+		if (owner.node.type === 'InlineComponent') {
+			break;
+		}
+
+		if (owner.node.type === 'Element' && /-/.test(owner.node.name)) {
+			break;
+		}
+
+		owner = owner.parent;
+	}
+	return owner;
+}

src/compiler/compile/render_dom/wrappers/Element/index.ts

@@ -2,7 +2,7 @@ import Renderer from '../../Renderer';
 import Element from '../../../nodes/Element';
 import Wrapper from '../shared/Wrapper';
 import Block from '../../Block';
-import { is_void, sanitize } from '../../../../utils/names';
+import { is_void } from '../../../../utils/names';
 import FragmentWrapper from '../Fragment';
 import { escape_html, string_literal } from '../../../utils/stringify';
 import TextWrapper from '../Text';
@@ -14,12 +14,9 @@ import StyleAttributeWrapper from './StyleAttribute';
 import SpreadAttributeWrapper from './SpreadAttribute';
 import { dimensions } from '../../../../utils/patterns';
 import Binding from './Binding';
-import InlineComponentWrapper from '../InlineComponent';
 import add_to_set from '../../../utils/add_to_set';
 import { add_event_handler } from '../shared/add_event_handlers';
 import { add_action } from '../shared/add_actions';
-import create_debugging_comment from '../shared/create_debugging_comment';
-import { get_slot_definition } from '../shared/get_slot_definition';
 import bind_this from '../shared/bind_this';
 import { is_head } from '../shared/is_head';
 import { Identifier } from 'estree';
@@ -28,6 +25,7 @@ import { extract_names } from 'periscopic';
 import Action from '../../../nodes/Action';
 import MustacheTagWrapper from '../MustacheTag';
 import RawMustacheTagWrapper from '../RawMustacheTag';
+import create_slot_block from './create_slot_block';
 
 interface BindingGroup {
 	events: string[];
@@ -177,47 +175,7 @@ export default class ElementWrapper extends Wrapper {
 
 		this.attributes = this.node.attributes.map(attribute => {
 			if (attribute.name === 'slot') {
-				// TODO make separate subclass for this?
-				let owner = this.parent;
-				while (owner) {
-					if (owner.node.type === 'InlineComponent') {
-						break;
-					}
-
-					if (owner.node.type === 'Element' && /-/.test(owner.node.name)) {
-						break;
-					}
-
-					owner = owner.parent;
-				}
-
-				if (owner && owner.node.type === 'InlineComponent') {
-					const name = attribute.get_static_value() as string;
-
-					if (!(owner as unknown as InlineComponentWrapper).slots.has(name)) {
-						const child_block = block.child({
-							comment: create_debugging_comment(node, this.renderer.component),
-							name: this.renderer.component.get_unique_name(`create_${sanitize(name)}_slot`),
-							type: 'slot'
-						});
-
-						const { scope, lets } = this.node;
-						const seen = new Set(lets.map(l => l.name.name));
-
-						(owner as unknown as InlineComponentWrapper).node.lets.forEach(l => {
-							if (!seen.has(l.name.name)) lets.push(l);
-						});
-
-						(owner as unknown as InlineComponentWrapper).slots.set(
-							name,
-							get_slot_definition(child_block, scope, lets)
-						);
-						this.renderer.blocks.push(child_block);
-					}
-
-					this.slot_block = (owner as unknown as InlineComponentWrapper).slots.get(name).block;
-					block = this.slot_block;
-				}
+				block = create_slot_block(attribute, this, block);
 			}
 			if (attribute.name === 'style') {
 				return new StyleAttributeWrapper(this, block, attribute);

src/compiler/compile/render_dom/wrappers/Slot.ts

@@ -12,11 +12,13 @@ import Expression from '../../nodes/shared/Expression';
 import is_dynamic from './shared/is_dynamic';
 import { Identifier, ObjectExpression } from 'estree';
 import create_debugging_comment from './shared/create_debugging_comment';
+import create_slot_block from './Element/create_slot_block';
 
 export default class SlotWrapper extends Wrapper {
 	node: Slot;
 	fragment: FragmentWrapper;
 	fallback: Block | null = null;
+	slot_block: Block;
 
 	var: Identifier = { type: 'Identifier', name: 'slot' };
 	dependencies: Set<string> = new Set(['$$scope']);
@@ -42,6 +44,10 @@ export default class SlotWrapper extends Wrapper {
 			renderer.blocks.push(this.fallback);
 		}
 
+		if (this.node.values.has('slot')) {
+			block = create_slot_block(this.node.values.get('slot'), this, block);
+		}
+
 		this.fragment = new FragmentWrapper(
 			renderer,
 			this.fallback,
@@ -71,6 +77,10 @@ export default class SlotWrapper extends Wrapper {
 
 		const { slot_name } = this.node;
 
+		if (this.slot_block) {
+			block = this.slot_block;
+		}
+
 		let get_slot_changes_fn;
 		let get_slot_context_fn;
 

src/compiler/compile/render_ssr/handlers/Slot.ts

@@ -2,9 +2,18 @@ import Renderer, { RenderOptions } from '../Renderer';
 import Slot from '../../nodes/Slot';
 import { x } from 'code-red';
 import get_slot_data from '../../utils/get_slot_data';
+import { get_slot_scope } from './shared/get_slot_scope';
 
-export default function(node: Slot, renderer: Renderer, options: RenderOptions) {
+export default function(node: Slot, renderer: Renderer, options: RenderOptions & {
+	slot_scopes: Map<any, any>;
+}) {
 	const slot_data = get_slot_data(node.values);
+	const slot = node.get_static_attribute_value('slot');
+	const nearest_inline_component = node.find_nearest(/InlineComponent/);
+
+	if (slot && nearest_inline_component) {
+		renderer.push();
+	}
 
 	renderer.push();
 	renderer.render(node.children, options);
@@ -15,4 +24,17 @@ export default function(node: Slot, renderer: Renderer, options: RenderOptions)
 			? #slots.${node.slot_name}(${slot_data})
 			: ${result}
 	`);
+
+	if (slot && nearest_inline_component) {
+		const lets = node.lets;
+		const seen = new Set(lets.map(l => l.name.name));
+
+		nearest_inline_component.lets.forEach(l => {
+			if (!seen.has(l.name.name)) lets.push(l);
+		});
+		options.slot_scopes.set(slot, {
+			input: get_slot_scope(node.lets),
+			output: renderer.pop()
+		});
+	}
 }

test/runtime/samples/component-slot-nested-in-slot/One.svelte

@@ -0,0 +1,8 @@
+<script>
+	import Two from './Two.svelte';
+	export let a, b;
+</script>
+
+<Two {b} let:two>
+	<slot name="one" slot="two" one={a} two={two}></slot>
+</Two>

test/runtime/samples/component-slot-nested-in-slot/Two.svelte

@@ -0,0 +1,4 @@
+<script>
+  export let b;
+</script>
+<slot name="two" two={b}></slot>

test/runtime/samples/component-slot-nested-in-slot/_config.js

@@ -0,0 +1,18 @@
+export default {
+	html: `
+		<p slot='one'>one: 1 two: 2</p>
+	`,
+	test({ assert, component, target }) {
+		component.a = 3;
+		component.b = 4;
+		assert.htmlEqual(target.innerHTML, `
+			<p slot='one'>one: 3 two: 4</p>
+		`);
+
+		component.a = 5;
+		component.b = 6;
+		assert.htmlEqual(target.innerHTML, `
+			<p slot='one'>one: 5 two: 6</p>
+		`);
+	}
+};

test/runtime/samples/component-slot-nested-in-slot/main.svelte

@@ -0,0 +1,9 @@
+<script>
+	import One from './One.svelte';
+	export let a = 1;
+	export let b = 2;
+</script>
+
+<One {a} {b}>
+	<p slot='one' let:one let:two>one: {one} two: {two}</p>
+</One>