a11y checks

src/generators/dom/preprocess.ts

@@ -1,7 +1,7 @@
 import Block from './Block';
 import { trimStart, trimEnd } from '../../utils/trim';
 import { assign } from '../../shared/index.js';
-import getStaticAttributeValue from '../shared/getStaticAttributeValue';
+import getStaticAttributeValue from '../../utils/getStaticAttributeValue';
 import { DomGenerator } from './index';
 import { Node } from '../../interfaces';
 import { State } from './interfaces';

src/generators/dom/visitors/Element/Attribute.ts

@@ -3,7 +3,7 @@ import deindent from '../../../../utils/deindent';
 import visitStyleAttribute, { optimizeStyle } from './StyleAttribute';
 import { stringify } from '../../../../utils/stringify';
 import getExpressionPrecedence from '../../../../utils/getExpressionPrecedence';
-import getStaticAttributeValue from '../../../shared/getStaticAttributeValue';
+import getStaticAttributeValue from '../../../../utils/getStaticAttributeValue';
 import { DomGenerator } from '../../index';
 import Block from '../../Block';
 import { Node } from '../../../../interfaces';

src/generators/dom/visitors/Element/Binding.ts

@@ -1,6 +1,6 @@
 import deindent from '../../../../utils/deindent';
 import flattenReference from '../../../../utils/flattenReference';
-import getStaticAttributeValue from '../../../shared/getStaticAttributeValue';
+import getStaticAttributeValue from '../../../../utils/getStaticAttributeValue';
 import { DomGenerator } from '../../index';
 import Block from '../../Block';
 import { Node } from '../../../../interfaces';

src/generators/dom/visitors/Element/Element.ts

@@ -8,7 +8,7 @@ import visitEventHandler from './EventHandler';
 import visitBinding from './Binding';
 import visitRef from './Ref';
 import * as namespaces from '../../../../utils/namespaces';
-import getStaticAttributeValue from '../../../shared/getStaticAttributeValue';
+import getStaticAttributeValue from '../../../../utils/getStaticAttributeValue';
 import addTransitions from './addTransitions';
 import { DomGenerator } from '../../index';
 import Block from '../../Block';
@@ -102,7 +102,7 @@ export default function visitElement(
 
 		if (node._cssRefAttribute) {
 			block.builders.hydrate.addLine(
-				`@setAttribute(${name}, "svelte-ref-${node._cssRefAttribute}", ");`
+				`@setAttribute(${name}, "svelte-ref-${node._cssRefAttribute}", "");`
 			)
 		}
 	}

src/generators/dom/visitors/Element/StyleAttribute.ts

@@ -2,7 +2,7 @@ import attributeLookup from './lookup';
 import deindent from '../../../../utils/deindent';
 import { stringify } from '../../../../utils/stringify';
 import getExpressionPrecedence from '../../../../utils/getExpressionPrecedence';
-import getStaticAttributeValue from '../../../shared/getStaticAttributeValue';
+import getStaticAttributeValue from '../../../../utils/getStaticAttributeValue';
 import { DomGenerator } from '../../index';
 import Block from '../../Block';
 import { Node } from '../../../../interfaces';

src/generators/dom/visitors/Slot.ts

@@ -2,7 +2,7 @@ import { DomGenerator } from '../index';
 import deindent from '../../../utils/deindent';
 import visit from '../visit';
 import Block from '../Block';
-import getStaticAttributeValue from '../../shared/getStaticAttributeValue';
+import getStaticAttributeValue from '../../../utils/getStaticAttributeValue';
 import { Node } from '../../../interfaces';
 import { State } from '../interfaces';
 

src/interfaces.ts

@@ -54,7 +54,7 @@ export interface CompileOptions {
 	cascade?: boolean;
 	hydratable?: boolean;
 	legacy?: boolean;
-	customElement: CustomElementOptions | true;
+	customElement?: CustomElementOptions | true;
 
 	onerror?: (error: Error) => void;
 	onwarn?: (warning: Warning) => void;

src/utils/getStaticAttributeValue.ts

@@ -0,0 +1,17 @@
+import { Node } from '../interfaces';
+
+export default function getStaticAttributeValue(node: Node, name: string) {
+	const attribute = node.attributes.find(
+		(attr: Node) => attr.name.toLowerCase() === name
+	);
+
+	if (!attribute) return null;
+
+	if (attribute.value.length === 0) return '';
+
+	if (attribute.value.length === 1 && attribute.value[0].type === 'Text') {
+		return attribute.value[0].data;
+	}
+
+	return null;
+}

src/validate/html/a11y.ts

@@ -0,0 +1,171 @@
+import * as namespaces from '../../utils/namespaces';
+import getStaticAttributeValue from '../../utils/getStaticAttributeValue';
+import fuzzymatch from '../utils/fuzzymatch';
+import validateEventHandler from './validateEventHandler';
+import { Validator } from '../index';
+import { Node } from '../../interfaces';
+
+const ariaAttributes = 'activedescendant atomic autocomplete busy checked controls describedby disabled dropeffect expanded flowto grabbed haspopup hidden invalid label labelledby level live multiline multiselectable orientation owns posinset pressed readonly relevant required selected setsize sort valuemax valuemin valuenow valuetext'.split(' ');
+const ariaAttributeSet = new Set(ariaAttributes);
+
+const ariaRoles = 'alert alertdialog application article banner button checkbox columnheader combobox command complementary composite contentinfo definition dialog directory document form grid gridcell group heading img input landmark link list listbox listitem log main marquee math menu menubar menuitem menuitemcheckbox menuitemradio navigation note option presentation progressbar radio radiogroup range region roletype row rowgroup rowheader scrollbar search section sectionhead select separator slider spinbutton status structure tab tablist tabpanel textbox timer toolbar tooltip tree treegrid treeitem widget window'.split(' ');
+const ariaRoleSet = new Set(ariaRoles);
+
+const invisibleElements = new Set(['meta', 'html', 'script', 'style']);
+
+export default function a11y(
+	validator: Validator,
+	node: Node,
+	elementStack: Node[]
+) {
+	if (node.type === 'Text') {
+		// accessible-emoji
+		return;
+	}
+
+	if (node.type !== 'Element') return;
+
+	const attributeMap = new Map();
+	node.attributes.forEach((attribute: Node) => {
+		const name = attribute.name.toLowerCase();
+
+		// aria-props
+		if (name.startsWith('aria-')) {
+			if (invisibleElements.has(node.name)) {
+				// aria-unsupported-elements
+				validator.warn(`A11y: <${node.name}> should not have aria-* attributes`, attribute.start);
+			}
+
+			const type = name.slice(5);
+			if (!ariaAttributeSet.has(type)) {
+				const match = fuzzymatch(type, ariaAttributes);
+				let message = `A11y: Unknown aria attribute 'aria-${type}'`;
+				if (match) message += ` (did you mean '${match}'?)`;
+
+				validator.warn(message, attribute.start);
+			}
+		}
+
+		// aria-role
+		if (name === 'role') {
+			if (invisibleElements.has(node.name)) {
+				// aria-unsupported-elements
+				validator.warn(`A11y: <${node.name}> should not have role attribute`, attribute.start);
+			}
+
+			const value = getStaticAttributeValue(node, 'role');
+			if (value && !ariaRoleSet.has(value)) {
+				const match = fuzzymatch(value, ariaRoles);
+				let message = `A11y: Unknown role '${value}'`;
+				if (match) message += ` (did you mean '${match}'?)`;
+
+				validator.warn(message, attribute.start);
+			}
+		}
+
+		// no-access-key
+		if (name === 'accesskey') {
+			validator.warn(`A11y: Avoid using accesskey`, attribute.start);
+		}
+
+		// no-autofocus
+		if (name === 'autofocus') {
+			validator.warn(`A11y: Avoid using autofocus`, attribute.start);
+		}
+
+		// scope
+		if (name === 'scope' && node.name !== 'th') {
+			validator.warn(`A11y: The scope attribute should only be used with <th> elements`, attribute.start);
+		}
+
+		// tabindex-no-positive
+		if (name === 'tabindex') {
+			const value = getStaticAttributeValue(node, 'tabindex');
+			if (!isNaN(value) && +value > 0) {
+				validator.warn(`A11y: avoid tabindex values above zero`, attribute.start);
+			}
+		}
+
+		attributeMap.set(attribute.name, attribute);
+	});
+
+	function shouldHaveAttribute(attributes: string[], name = node.name) {
+		if (attributes.length === 0 || !attributes.some((name: string) => attributeMap.has(name))) {
+			const article = /^[aeiou]/.test(attributes[0]) ? 'an' : 'a';
+			const sequence = attributes.length > 1 ?
+				attributes.slice(0, -1).join(', ') + ` or ${attributes[attributes.length - 1]}` :
+				attributes[0];
+
+			validator.warn(`A11y: <${name}> element should have ${article} ${sequence} attribute`, node.start);
+		}
+	}
+
+	function shouldHaveContent() {
+		if (node.children.length === 0) {
+			validator.warn(`A11y: <${node.name}> element should have child content`, node.start);
+		}
+	}
+
+	if (node.name === 'a') {
+		// anchor-is-valid
+		const href = attributeMap.get('href');
+		if (attributeMap.has('href')) {
+			const value = getStaticAttributeValue(node, 'href');
+			if (value === '' || value === '#') {
+				validator.warn(`A11y: '${value}' is not a valid href attribute`, href.start);
+			}
+		} else {
+			validator.warn(`A11y: <a> element should have an href attribute`, node.start);
+		}
+
+		// anchor-has-content
+		shouldHaveContent();
+	}
+
+	if (node.name === 'img') shouldHaveAttribute(['alt']);
+	if (node.name === 'area') shouldHaveAttribute(['alt', 'aria-label', 'aria-labelledby']);
+	if (node.name === 'object') shouldHaveAttribute(['title', 'aria-label', 'aria-labelledby']);
+	if (node.name === 'input' && getStaticAttributeValue(node, 'type') === 'image') {
+		shouldHaveAttribute(['alt', 'aria-label', 'aria-labelledby'], 'input type="image"');
+	}
+
+	// heading-has-content
+	if (/^h[1-6]$/.test(node.name)) {
+		shouldHaveContent();
+
+		if (attributeMap.has('aria-hidden')) {
+			validator.warn(`A11y: <${node.name}> element should not be hidden`, attributeMap.get('aria-hidden').start);
+		}
+	}
+
+	// iframe-has-title
+	if (node.name === 'iframe') {
+		shouldHaveAttribute(['title']);
+	}
+
+	// no-distracting-elements
+	if (node.name === 'marquee' || node.name === 'blink') {
+		validator.warn(`A11y: Avoid <${node.name}> elements`, node.start);
+	}
+
+	if (node.name === 'figcaption') {
+		const parent = elementStack[elementStack.length - 1];
+		if (parent) {
+			if (parent.name !== 'figure') {
+				validator.warn(`A11y: <figcaption> must be an immediate child of <figure>`, node.start);
+			} else {
+				const index = parent.children.indexOf(node);
+				if (index !== 0 && index !== parent.children.length - 1) {
+					validator.warn(`A11y: <figcaption> must be first or last child of <figure>`, node.start);
+				}
+			}
+		}
+	}
+}
+
+function getValue(attribute: Node) {
+	if (attribute.value.length === 0) return '';
+	if (attribute.value.length === 1 && attribute.value[0].type === 'Text') return attribute.value[0].data;
+
+	return null;
+}

src/validate/html/index.ts

@@ -1,41 +1,27 @@
-import * as namespaces from '../../utils/namespaces';
 import validateElement from './validateElement';
 import validateWindow from './validateWindow';
+import a11y from './a11y';
 import fuzzymatch from '../utils/fuzzymatch'
 import flattenReference from '../../utils/flattenReference';
 import { Validator } from '../index';
 import { Node } from '../../interfaces';
 
-const svg = /^(?:altGlyph|altGlyphDef|altGlyphItem|animate|animateColor|animateMotion|animateTransform|circle|clipPath|color-profile|cursor|defs|desc|discard|ellipse|feBlend|feColorMatrix|feComponentTransfer|feComposite|feConvolveMatrix|feDiffuseLighting|feDisplacementMap|feDistantLight|feDropShadow|feFlood|feFuncA|feFuncB|feFuncG|feFuncR|feGaussianBlur|feImage|feMerge|feMergeNode|feMorphology|feOffset|fePointLight|feSpecularLighting|feSpotLight|feTile|feTurbulence|filter|font|font-face|font-face-format|font-face-name|font-face-src|font-face-uri|foreignObject|g|glyph|glyphRef|hatch|hatchpath|hkern|image|line|linearGradient|marker|mask|mesh|meshgradient|meshpatch|meshrow|metadata|missing-glyph|mpath|path|pattern|polygon|polyline|radialGradient|rect|set|solidcolor|stop|switch|symbol|text|textPath|title|tref|tspan|unknown|use|view|vkern)$/;
-
 const meta = new Map([[':Window', validateWindow]]);
 
 export default function validateHtml(validator: Validator, html: Node) {
-	let elementDepth = 0;
-
 	const refs = new Map();
 	const refCallees: Node[] = [];
+	const elementStack: Node[] = [];
 
 	function visit(node: Node) {
-		if (node.type === 'Element') {
-			if (
-				elementDepth === 0 &&
-				validator.namespace !== namespaces.svg &&
-				svg.test(node.name)
-			) {
-				validator.warn(
-					`<${node.name}> is an SVG element – did you forget to add { namespace: 'svg' } ?`,
-					node.start
-				);
-			}
+		a11y(validator, node, elementStack);
 
+		if (node.type === 'Element') {
 			if (meta.has(node.name)) {
 				return meta.get(node.name)(validator, node, refs, refCallees);
 			}
 
-			elementDepth += 1;
-
-			validateElement(validator, node, refs, refCallees);
+			validateElement(validator, node, refs, refCallees, elementStack);
 		} else if (node.type === 'EachBlock') {
 			if (validator.helpers.has(node.context)) {
 				let c = node.expression.end;
@@ -53,16 +39,14 @@ export default function validateHtml(validator: Validator, html: Node) {
 		}
 
 		if (node.children) {
+			if (node.type === 'Element') elementStack.push(node);
 			node.children.forEach(visit);
+			if (node.type === 'Element') elementStack.pop();
 		}
 
 		if (node.else) {
 			visit(node.else);
 		}
-
-		if (node.type === 'Element') {
-			elementDepth -= 1;
-		}
 	}
 
 	html.children.forEach(visit);

src/validate/html/validateElement.ts

@@ -1,8 +1,17 @@
+import * as namespaces from '../../utils/namespaces';
 import validateEventHandler from './validateEventHandler';
 import { Validator } from '../index';
 import { Node } from '../../interfaces';
 
-export default function validateElement(validator: Validator, node: Node, refs: Map<string, Node[]>, refCallees: Node[]) {
+const svg = /^(?:altGlyph|altGlyphDef|altGlyphItem|animate|animateColor|animateMotion|animateTransform|circle|clipPath|color-profile|cursor|defs|desc|discard|ellipse|feBlend|feColorMatrix|feComponentTransfer|feComposite|feConvolveMatrix|feDiffuseLighting|feDisplacementMap|feDistantLight|feDropShadow|feFlood|feFuncA|feFuncB|feFuncG|feFuncR|feGaussianBlur|feImage|feMerge|feMergeNode|feMorphology|feOffset|fePointLight|feSpecularLighting|feSpotLight|feTile|feTurbulence|filter|font|font-face|font-face-format|font-face-name|font-face-src|font-face-uri|foreignObject|g|glyph|glyphRef|hatch|hatchpath|hkern|image|line|linearGradient|marker|mask|mesh|meshgradient|meshpatch|meshrow|metadata|missing-glyph|mpath|path|pattern|polygon|polyline|radialGradient|rect|set|solidcolor|stop|switch|symbol|text|textPath|title|tref|tspan|unknown|use|view|vkern)$/;
+
+export default function validateElement(
+	validator: Validator,
+	node: Node,
+	refs: Map<string, Node[]>,
+	refCallees: Node[],
+	elementStack: Node[]
+) {
 	const isComponent =
 		node.name === ':Self' || validator.components.has(node.name);
 
@@ -11,6 +20,13 @@ export default function validateElement(validator: Validator, node: Node, refs:
 		validator.warn(`${node.name} component is not defined`, node.start);
 	}
 
+	if (elementStack.length === 0 && validator.namespace !== namespaces.svg && svg.test(node.name)) {
+		validator.warn(
+			`<${node.name}> is an SVG element – did you forget to add { namespace: 'svg' } ?`,
+			node.start
+		);
+	}
+
 	if (node.name === 'slot') {
 		const nameAttribute = node.attributes.find((attribute: Node) => attribute.name === 'name');
 		if (nameAttribute) {

src/validate/js/index.ts

@@ -57,14 +57,12 @@ export default function validateJs(validator: Validator, js: Node) {
 					const match = fuzzymatch(prop.key.name, validPropList);
 					if (match) {
 						validator.error(
-							`Unexpected property '${prop.key
-								.name}' (did you mean '${match}'?)`,
+							`Unexpected property '${prop.key.name}' (did you mean '${match}'?)`,
 							prop.start
 						);
 					} else if (/FunctionExpression/.test(prop.value.type)) {
 						validator.error(
-							`Unexpected property '${prop.key
-								.name}' (did you mean to include it in 'methods'?)`,
+							`Unexpected property '${prop.key.name}' (did you mean to include it in 'methods'?)`,
 							prop.start
 						);
 					} else {