slot validation

packages/svelte/src/compiler/errors.js

@@ -252,13 +252,19 @@ const attributes = {
 const slots = {
 	'invalid-slot-element-attribute': () => `<slot> can only receive attributes, not directives`,
 	'invalid-slot-attribute': () => `slot attribute must be a static value`,
-	'invalid-slot-name': () => `slot attribute must be a static value`,
+	/** @param {boolean} is_default */
+	'invalid-slot-name': (is_default) =>
+		is_default
+			? `default is a reserved word — it cannot be used as a slot name`
+			: `slot attribute must be a static value`,
 	'invalid-slot-placement': () =>
 		`Element with a slot='...' attribute must be a child of a component or a descendant of a custom element`,
-	'duplicate-slot-name': /** @param {string} name @param {string} component */ (name, component) =>
+	/** @param {string} name @param {string} component */
-		`Duplicate slot name '${name}' in <${component}>`,
+	'duplicate-slot-name': (name, component) => `Duplicate slot name '${name}' in <${component}>`,
 	'invalid-default-slot-content': () =>
-		`Found default slot content alongside an explicit slot="default"`
+		`Found default slot content alongside an explicit slot="default"`,
+	/** @param {string} name */
+	'duplicate-slot-declaration': (name) => `duplicate ${name} <slot> element`
 };
 
 /** @satisfies {Errors} */
@@ -358,10 +364,6 @@ const errors = {
 	// 	code: 'dynamic-slot-name',
 	// 	message: '<slot> name cannot be dynamic'
 	// },
-	// invalid_slot_name: {
-	// 	code: 'invalid-slot-name',
-	// 	message: 'default is a reserved word — it cannot be used as a slot name'
-	// },
 	// invalid_slot_attribute_value_missing: {
 	// 	code: 'invalid-slot-attribute',
 	// 	message: 'slot attribute value is missing'

packages/svelte/src/compiler/phases/2-analyze/index.js

@@ -364,6 +364,7 @@ export function analyze_component(root, options) {
 				ast_type: ast === instance.ast ? 'instance' : ast === template.ast ? 'template' : 'module',
 				parent_element: null,
 				has_props_rune: false,
+				slots: new Set(),
 				component_slots: new Set(),
 				expression: null,
 				private_derived_state: [],
@@ -401,6 +402,7 @@ export function analyze_component(root, options) {
 				instance_scope: instance.scope,
 				reactive_statement: null,
 				reactive_statements: analysis.reactive_statements,
+				slots: new Set(),
 				component_slots: new Set(),
 				expression: null,
 				private_derived_state: [],

packages/svelte/src/compiler/phases/2-analyze/types.d.ts

@@ -16,6 +16,7 @@ export interface AnalysisState {
 	ast_type: 'instance' | 'template' | 'module';
 	parent_element: string | null;
 	has_props_rune: boolean;
+	slots: Set<string>;
 	/** Which slots the current parent component has */
 	component_slots: Set<string>;
 	/** The current {expression}, if any */

packages/svelte/src/compiler/phases/2-analyze/validation.js

@@ -485,18 +485,35 @@ export const validation = {
 			}
 		}
 	},
-	SlotElement(node) {
+	SlotElement(node, context) {
+		let is_named_slot = false;
+
 		for (const attribute of node.attributes) {
 			if (attribute.type === 'Attribute') {
 				if (attribute.name === 'name') {
 					if (!is_text_attribute(attribute)) {
-						error(attribute, 'invalid-slot-name');
+						error(attribute, 'invalid-slot-name', false);
+					}
+					const slot_name = attribute.value[0].data;
+					if (slot_name === 'default') {
+						error(attribute, 'invalid-slot-name', true);
+					} else if (context.state.slots.has(slot_name)) {
+						error(attribute, 'duplicate-slot-declaration', `'${slot_name}'`);
 					}
+					context.state.slots.add(slot_name);
+					is_named_slot = true;
 				}
 			} else if (attribute.type !== 'SpreadAttribute') {
 				error(attribute, 'invalid-slot-element-attribute');
 			}
 		}
+
+		if (!is_named_slot) {
+			if (context.state.slots.has('default')) {
+				error(node, 'duplicate-slot-declaration', 'default');
+			}
+			context.state.slots.add('default');
+		}
 	},
 	Component: validate_component,
 	SvelteComponent: validate_component,

packages/svelte/tests/validator/samples/component-slot-default-duplicate/_config.js

@@ -1,3 +0,0 @@
-import { test } from '../../test';
-
-export default test({ skip: true });

packages/svelte/tests/validator/samples/component-slot-default-duplicate/errors.json

@@ -1,9 +1,14 @@
 [
 	{
+		"code": "duplicate-slot-declaration",
 		"message": "duplicate default <slot> element",
 		"start": {
 			"line": 2,
 			"column": 0
+		},
+		"end": {
+			"line": 2,
+			"column": 13
 		}
 	}
 ]

packages/svelte/tests/validator/samples/component-slot-default-reserved/_config.js

@@ -1,3 +0,0 @@
-import { test } from '../../test';
-
-export default test({ skip: true });

packages/svelte/tests/validator/samples/component-slot-dynamic-attribute/_config.js

@@ -1,3 +0,0 @@
-import { test } from '../../test';
-
-export default test({ skip: true });

packages/svelte/tests/validator/samples/component-slot-dynamic-attribute/errors.json

@@ -1,7 +1,7 @@
 [
 	{
 		"code": "invalid-slot-attribute",
-		"message": "slot attribute cannot have a dynamic value",
+		"message": "slot attribute must be a static value",
 		"start": {
 			"line": 6,
 			"column": 9

packages/svelte/tests/validator/samples/component-slot-dynamic/_config.js

@@ -1,3 +0,0 @@
-import { test } from '../../test';
-
-export default test({ skip: true });

packages/svelte/tests/validator/samples/component-slot-dynamic/errors.json

@@ -1,7 +1,7 @@
 [
 	{
-		"code": "dynamic-slot-name",
+		"code": "invalid-slot-name",
-		"message": "<slot> name cannot be dynamic",
+		"message": "slot attribute must be a static value",
 		"start": {
 			"line": 1,
 			"column": 6

packages/svelte/tests/validator/samples/component-slot-named-duplicate/_config.js

@@ -1,3 +0,0 @@
-import { test } from '../../test';
-
-export default test({ skip: true });

packages/svelte/tests/validator/samples/component-slot-named-duplicate/errors.json

@@ -1,9 +1,14 @@
 [
 	{
+		"code": "duplicate-slot-declaration",
 		"message": "duplicate 'foo' <slot> element",
 		"start": {
 			"line": 2,
 			"column": 6
+		},
+		"end": {
+			"line": 2,
+			"column": 16
 		}
 	}
 ]

packages/svelte/tests/validator/samples/component-slotted-custom-element-2/_config.js

@@ -1,3 +0,0 @@
-import { test } from '../../test';
-
-export default test({ skip: true });

packages/svelte/tests/validator/samples/component-slotted-custom-element-2/errors.json

@@ -1,6 +1,6 @@
 [
 	{
-		"code": "invalid-slotted-content",
+		"code": "invalid-slot-placement",
 		"message": "Element with a slot='...' attribute must be a child of a component or a descendant of a custom element",
 		"start": { "line": 10, "column": 9 },
 		"end": { "line": 10, "column": 19 }

packages/svelte/tests/validator/samples/component-slotted-each-block/_config.js

@@ -1,3 +0,0 @@
-import { test } from '../../test';
-
-export default test({ skip: true });

packages/svelte/tests/validator/samples/component-slotted-each-block/errors.json

@@ -1,6 +1,6 @@
 [
 	{
-		"code": "invalid-slotted-content",
+		"code": "invalid-slot-placement",
 		"message": "Element with a slot='...' attribute must be a child of a component or a descendant of a custom element",
 		"start": {
 			"line": 7,

packages/svelte/tests/validator/samples/component-slotted-if-block/_config.js

@@ -1,3 +0,0 @@
-import { test } from '../../test';
-
-export default test({ skip: true });

packages/svelte/tests/validator/samples/component-slotted-if-block/errors.json

@@ -1,6 +1,6 @@
 [
 	{
-		"code": "invalid-slotted-content",
+		"code": "invalid-slot-placement",
 		"message": "Element with a slot='...' attribute must be a child of a component or a descendant of a custom element",
 		"start": {
 			"line": 7,