implement <svelte:fragment>

add validation and test

replace svelte:slot -> svelte:fragment

slot as a sugar syntax

fix eslint

src/compiler/compile/nodes/DefaultSlotTemplate.ts

@@ -0,0 +1,28 @@
+import Component from '../Component';
+import TemplateScope from './shared/TemplateScope';
+import Node from './shared/Node';
+import Let from './Let';
+import { INode } from './interfaces';
+
+export default class DefaultSlotTemplate extends Node {
+	type: 'SlotTemplate';
+	scope: TemplateScope;
+	children: INode[];
+	lets: Let[] = [];
+	slot_template_name = 'default';
+
+	constructor(
+		component: Component,
+		parent: INode,
+		scope: TemplateScope,
+		info: any,
+		lets: Let[],
+		children: INode[]
+	) {
+		super(component, parent, scope, info);
+		this.type = 'SlotTemplate';
+		this.children = children;
+		this.scope = scope;
+		this.lets = lets;
+	}
+}

src/compiler/compile/nodes/Element.ts

@@ -429,7 +429,7 @@ export default class Element extends Node {
 					component.slot_outlets.add(name);
 				}
 
-				if (!(parent.type === 'InlineComponent' || within_custom_element(parent))) {
+				if (!(parent.type === 'SlotTemplate' || within_custom_element(parent))) {
 					component.error(attribute, {
 						code: 'invalid-slotted-content',
 						message: 'Element with a slot=\'...\' attribute must be a child of a component or a descendant of a custom element'
@@ -863,6 +863,10 @@ export default class Element extends Node {
 			);
 		}
 	}
+
+	get slot_template_name() {
+		return this.attributes.find(attribute => attribute.name === 'slot').get_static_value() as string;
+	}
 }
 
 function should_have_attribute(

src/compiler/compile/nodes/InlineComponent.ts

@@ -45,12 +45,6 @@ export default class InlineComponent extends Node {
 					});
 
 				case 'Attribute':
-					if (node.name === 'slot') {
-						component.error(node, {
-							code: 'invalid-prop',
-							message: "'slot' is reserved for future use in named slots"
-						});
-					}
 					// fallthrough
 				case 'Spread':
 					this.attributes.push(new Attribute(component, this, scope, node));
@@ -111,6 +105,57 @@ export default class InlineComponent extends Node {
 			});
 		});
 
-		this.children = map_children(component, this, this.scope, info.children);
+		const children = [];
+		for (let i=info.children.length - 1; i >= 0; i--) {
+			const child = info.children[i];
+			if (child.type === 'SlotTemplate') {
+				children.push(child);
+				info.children.splice(i, 1);
+			} else if ((child.type === 'Element' || child.type === 'InlineComponent' || child.type === 'Slot') && child.attributes.find(attribute => attribute.name === 'slot')) {
+				const slot_template = {
+					start: child.start,
+					end: child.end,
+					type: 'SlotTemplate',
+					name: 'svelte:fragment',
+					attributes: [],
+					children: [child]
+				};
+
+				// transfer attributes
+				for (let i=child.attributes.length - 1; i >= 0; i--) {
+					const attribute = child.attributes[i];
+					if (attribute.type === 'Let') {
+						slot_template.attributes.push(attribute);
+						child.attributes.splice(i, 1);
+					} else if (attribute.type === 'Attribute' && attribute.name === 'slot') {
+						slot_template.attributes.push(attribute);
+					}
+				}
+
+				children.push(slot_template);
+				info.children.splice(i, 1);
+			}
+		}
+
+		if (info.children.some(node => not_whitespace_text(node))) {
+			children.push({ 
+				start: info.start,
+				end: info.end,
+				type: 'SlotTemplate', 
+				name: 'svelte:fragment',
+				attributes: [],
+				children: info.children
+			});
+		}
+
+		this.children = map_children(component, this, this.scope, children);
+	}
+
+	get slot_template_name() {
+		return this.attributes.find(attribute => attribute.name === 'slot').get_static_value() as string;
 	}
 }
+
+function not_whitespace_text(node) {
+	return !(node.type === 'Text' && /^\s+$/.test(node.data));
+}

src/compiler/compile/nodes/SlotTemplate.ts

@@ -0,0 +1,82 @@
+import map_children from './shared/map_children';
+import Component from '../Component';
+import TemplateScope from './shared/TemplateScope';
+import Node from './shared/Node';
+import Let from './Let';
+import Attribute from './Attribute';
+import { INode } from './interfaces';
+
+export default class SlotTemplate extends Node {
+	type: 'SlotTemplate';
+	scope: TemplateScope;
+	children: INode[];
+	lets: Let[] = [];
+	slot_attribute: Attribute;
+	slot_template_name: string = 'default';
+
+	constructor(
+		component: Component,
+		parent: INode,
+		scope: TemplateScope,
+		info: any
+	) {
+		super(component, parent, scope, info);
+
+		this.validate_slot_template_placement();
+
+		const has_let = info.attributes.some((node) => node.type === 'Let');
+		if (has_let) {
+			scope = scope.child();
+		}
+
+		info.attributes.forEach((node) => {
+			switch (node.type) {
+				case 'Let': {
+					const l = new Let(component, this, scope, node);
+					this.lets.push(l);
+					const dependencies = new Set([l.name.name]);
+
+					l.names.forEach((name) => {
+						scope.add(name, dependencies, this);
+					});
+					break;
+				}
+				case 'Attribute': {
+					if (node.name === 'slot') {
+						this.slot_attribute = new Attribute(component, this, scope, node);
+						if (!this.slot_attribute.is_static) {
+							component.error(node, {
+								code: 'invalid-slot-attribute',
+								message: 'slot attribute cannot have a dynamic value'
+							});
+						}
+						const value = this.slot_attribute.get_static_value();
+						if (typeof value === 'boolean') {
+							component.error(node, {
+								code: 'invalid-slot-attribute',
+								message: 'slot attribute value is missing'
+							});
+						}
+						this.slot_template_name = value as string;
+						break;
+					}
+					throw new Error(`Invalid attribute '${node.name}' in <svelte:fragment>`);
+				}
+				default:
+					throw new Error(`Not implemented: ${node.type}`);
+			}
+		});
+
+		this.scope = scope;
+		this.children = map_children(component, this, this.scope, info.children);
+	}
+
+	validate_slot_template_placement() {
+		if (this.parent.type !== 'InlineComponent') {
+			this.component.error(this, {
+				code: 'invalid-slotted-content',
+				message: '<svelte:fragment> must be a child of a component'
+			});
+		}
+	}
+}

src/compiler/compile/nodes/Text.ts

@@ -29,7 +29,7 @@ export default class Text extends Node {
 	should_skip() {
 		if (/\S/.test(this.data)) return false;
 
-		const parent_element = this.find_nearest(/(?:Element|InlineComponent|Head)/);
+		const parent_element = this.find_nearest(/(?:Element|InlineComponent|SlotTemplate|Head)/);
 		if (!parent_element) return false;
 
 		if (parent_element.type === 'Head') return true;

src/compiler/compile/nodes/interfaces.ts

@@ -25,6 +25,8 @@ import Options from './Options';
 import PendingBlock from './PendingBlock';
 import RawMustacheTag from './RawMustacheTag';
 import Slot from './Slot';
+import SlotTemplate from './SlotTemplate';
+import DefaultSlotTemplate from './DefaultSlotTemplate';
 import Text from './Text';
 import ThenBlock from './ThenBlock';
 import Title from './Title';
@@ -58,6 +60,8 @@ export type INode = Action
 | PendingBlock
 | RawMustacheTag
 | Slot
+| SlotTemplate
+| DefaultSlotTemplate
 | Tag
 | Text
 | ThenBlock

src/compiler/compile/nodes/shared/TemplateScope.ts

@@ -3,8 +3,9 @@ import ThenBlock from '../ThenBlock';
 import CatchBlock from '../CatchBlock';
 import InlineComponent from '../InlineComponent';
 import Element from '../Element';
+import SlotTemplate from '../SlotTemplate';
 
-type NodeWithScope = EachBlock | ThenBlock | CatchBlock | InlineComponent | Element;
+type NodeWithScope = EachBlock | ThenBlock | CatchBlock | InlineComponent | Element | SlotTemplate;
 
 export default class TemplateScope {
 	names: Set<string>;
@@ -40,7 +41,7 @@ export default class TemplateScope {
 
 	is_let(name: string) {
 		const owner = this.get_owner(name);
-		return owner && (owner.type === 'Element' || owner.type === 'InlineComponent');
+		return owner && (owner.type === 'Element' || owner.type === 'InlineComponent' || owner.type === 'SlotTemplate');
 	}
 
 	is_await(name: string) {

src/compiler/compile/nodes/shared/map_children.ts

@@ -12,6 +12,7 @@ import Options from '../Options';
 import RawMustacheTag from '../RawMustacheTag';
 import DebugTag from '../DebugTag';
 import Slot from '../Slot';
+import SlotTemplate from '../SlotTemplate';
 import Text from '../Text';
 import Title from '../Title';
 import Window from '../Window';
@@ -35,6 +36,7 @@ function get_constructor(type) {
 		case 'RawMustacheTag': return RawMustacheTag;
 		case 'DebugTag': return DebugTag;
 		case 'Slot': return Slot;
+		case 'SlotTemplate': return SlotTemplate;
 		case 'Text': return Text;
 		case 'Title': return Title;
 		case 'Window': return Window;

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

@@ -25,7 +25,6 @@ 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[];
@@ -141,7 +140,6 @@ export default class ElementWrapper extends Wrapper {
 	event_handlers: EventHandler[];
 	class_dependencies: string[];
 
-	slot_block: Block;
 	select_binding_dependencies?: Set<string>;
 
 	var: any;
@@ -174,9 +172,6 @@ export default class ElementWrapper extends Wrapper {
 		}
 
 		this.attributes = this.node.attributes.map(attribute => {
-			if (attribute.name === 'slot') {
-				block = create_slot_block(attribute, this, block);
-			}
 			if (attribute.name === 'style') {
 				return new StyleAttributeWrapper(this, block, attribute);
 			}
@@ -231,26 +226,13 @@ export default class ElementWrapper extends Wrapper {
 		}
 
 		this.fragment = new FragmentWrapper(renderer, block, node.children, this, strip_whitespace, next_sibling);
-
-		if (this.slot_block) {
-			block.parent.add_dependencies(block.dependencies);
-
-			// appalling hack
-			const index = block.parent.wrappers.indexOf(this);
-			block.parent.wrappers.splice(index, 1);
-			block.wrappers.push(this);
-		}
 	}
 
 	render(block: Block, parent_node: Identifier, parent_nodes: Identifier) {
 		const { renderer } = this;
 
 		if (this.node.name === 'noscript') return;
 
-		if (this.slot_block) {
-			block = this.slot_block;
-		}
-
 		const node = this.var;
 		const nodes = parent_nodes && block.get_unique_name(`${this.var.name}_nodes`); // if we're in unclaimable territory, i.e. <head>, parent_nodes is null
 		const children = x`@children(${this.node.name === 'template' ? x`${node}.content` : node})`;

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

@@ -11,6 +11,7 @@ import InlineComponent from './InlineComponent/index';
 import MustacheTag from './MustacheTag';
 import RawMustacheTag from './RawMustacheTag';
 import Slot from './Slot';
+import SlotTemplate from './SlotTemplate';
 import Text from './Text';
 import Title from './Title';
 import Window from './Window';
@@ -36,6 +37,7 @@ const wrappers = {
 	Options: null,
 	RawMustacheTag,
 	Slot,
+	SlotTemplate,
 	Text,
 	Title,
 	Window