feat: add a11y interactive-supports-focus (#8392)

#820

site/content/docs/06-accessibility-warnings.md

@@ -137,6 +137,17 @@ Enforce that attributes important for accessibility have a valid value. For exam
 
 ---
 
+### `a11y-interactive-supports-focus`
+
+Enforce that elements with an interactive role and interactive handlers (mouse or key press) must be focusable or tabbable.
+
+```sv
+<!-- A11y: Elements with the 'button' interactive role must have a tabindex value. -->
+<div role="button" on:keypress={() => {}} />
+```
+
+---
+
 ### `a11y-label-has-associated-control`
 
 Enforce that a label tag has a text label and an associated control.

src/compiler/compile/compiler_warnings.ts

@@ -166,6 +166,10 @@ export default {
 		code: 'a11y-img-redundant-alt',
 		message: 'A11y: Screenreaders already announce <img> elements as an image.'
 	},
+	a11y_interactive_supports_focus: (role: string) => ({
+		code: 'a11y-interactive-supports-focus',
+		message: `A11y: Elements with the '${role}' interactive role must have a tabindex value.`
+	}),
 	a11y_label_has_associated_control: {
 		code: 'a11y-label-has-associated-control',
 		message: 'A11y: A form label must be associated with a control.'

src/compiler/compile/nodes/Element.ts

@@ -25,7 +25,7 @@ import { Literal } from 'estree';
 import compiler_warnings from '../compiler_warnings';
 import compiler_errors from '../compiler_errors';
 import { ARIARoleDefinitionKey, roles, aria, ARIAPropertyDefinition, ARIAProperty } from 'aria-query';
-import { is_interactive_element, is_non_interactive_element, is_non_interactive_roles, is_presentation_role, is_interactive_roles, is_hidden_from_screen_reader, is_semantic_role_element, is_abstract_role } from '../utils/a11y';
+import { is_interactive_element, is_non_interactive_element, is_non_interactive_roles, is_presentation_role, is_interactive_roles, is_hidden_from_screen_reader, is_semantic_role_element, is_abstract_role, is_static_element, has_disabled_attribute } from '../utils/a11y';
 
 const aria_attributes = 'activedescendant atomic autocomplete busy checked colcount colindex colspan controls current describedby description details disabled dropeffect errormessage expanded flowto grabbed haspopup hidden invalid keyshortcuts label labelledby level live modal multiline multiselectable orientation owns placeholder posinset pressed readonly relevant required roledescription rowcount rowindex rowspan selected setsize sort valuemax valuemin valuenow valuetext'.split(' ');
 const aria_attribute_set = new Set(aria_attributes);
@@ -75,6 +75,33 @@ const a11y_labelable = new Set([
 	'textarea'
 ]);
 
+const a11y_interactive_handlers = new Set([
+	// Keyboard events
+	'keypress',
+	'keydown',
+	'keyup',
+
+	// Click events
+	'click',
+	'contextmenu',
+	'dblclick',
+	'drag',
+	'dragend',
+	'dragenter',
+	'dragexit',
+	'dragleave',
+	'dragover',
+	'dragstart',
+	'drop',
+	'mousedown',
+	'mouseenter',
+	'mouseleave',
+	'mousemove',
+	'mouseout',
+	'mouseover',
+	'mouseup'
+]);
+
 const a11y_nested_implicit_semantics = new Map([
 	['header', 'banner'],
 	['footer', 'contentinfo']
@@ -603,6 +630,21 @@ export default class Element extends Node {
 							}
 						}
 
+						// interactive-supports-focus
+						if (
+							!has_disabled_attribute(attribute_map) &&
+							!is_hidden_from_screen_reader(this.name, attribute_map) &&
+							!is_presentation_role(current_role) &&
+							is_interactive_roles(current_role) &&
+							is_static_element(this.name, attribute_map) &&
+							!attribute_map.get('tabindex')
+						) {
+							const has_interactive_handlers = handlers.some((handler) => a11y_interactive_handlers.has(handler.name));
+							if (has_interactive_handlers) {
+								component.warn(this, compiler_warnings.a11y_interactive_supports_focus(current_role));
+							}
+						}
+
 						// no-interactive-element-to-noninteractive-role
 						if (is_interactive_element(this.name, attribute_map) && (is_non_interactive_roles(current_role) || is_presentation_role(current_role))) {
 							component.warn(this, compiler_warnings.a11y_no_interactive_element_to_noninteractive_role(current_role, this.name));

src/compiler/compile/utils/a11y.ts

@@ -68,6 +68,24 @@ export function is_hidden_from_screen_reader(tag_name: string, attribute_map: Ma
 	return aria_hidden_value === true || aria_hidden_value === 'true';
 }
 
+export function has_disabled_attribute(attribute_map: Map<string, Attribute>) {
+	const disabled_attr = attribute_map.get('disabled');
+	const disabled_attr_value = disabled_attr && disabled_attr.get_static_value();
+	if (disabled_attr_value) {
+		return true;
+	}
+
+	const aria_disabled_attr = attribute_map.get('aria-disabled');
+	if (aria_disabled_attr) {
+		const aria_disabled_attr_value = aria_disabled_attr.get_static_value();
+		if (aria_disabled_attr_value === true) {
+			return true;
+		}
+	}
+
+	return false;
+}
+
 const non_interactive_element_role_schemas: ARIARoleRelationConcept[] = [];
 
 elementRoles.entries().forEach(([schema, roles]) => {

test/validator/samples/a11y-interactive-supports-focus/input.svelte

@@ -0,0 +1,32 @@
+<!-- VALID -->
+<div aria-hidden role="button" on:keypress={() => {}} />
+<div aria-disabled role="button" on:keypress={() => {}} />
+<div disabled role="button" on:keypress={() => {}} />
+<div role="presentation" on:keypress={() => {}} />
+<button on:click={() => {}} />
+<div role="menuitem" tabindex="0" on:click={() => {}} on:keypress={() => {}} />
+<div role="button" tabindex="-1" on:click={() => {}} on:keypress={() => {}} />
+
+<!-- INVALID -->
+<div role="button" on:keypress={() => {}} />
+<span role="menuitem" on:keydown={() => {}} />
+<div role="button" on:keyup={() => {}} />
+<span role="menuitem" on:click={() => {}} on:keypress={() => {}} />
+<div role="button" on:contextmenu={() => {}} />
+<span role="menuitem" on:dblclick={() => {}} />
+<div role="button" on:drag={() => {}} />
+<span role="menuitem" on:dragend={() => {}} />
+<div role="button" on:dragenter={() => {}} />
+<span role="menuitem" on:dragexit={() => {}} />
+<div role="button" on:dragleave={() => {}} />
+<span role="menuitem" on:dragover={() => {}} />
+<div role="button" on:dragstart={() => {}} />
+<span role="menuitem" on:drop={() => {}} />
+<div role="button" on:mousedown={() => {}} />
+<span role="menuitem" on:mouseenter={() => {}} />
+<div role="button" on:mouseleave={() => {}} />
+<span role="menuitem" on:mousemove={() => {}} />
+<div role="button" on:mouseout={() => {}} />
+<span role="menuitem" on:mouseover={() => {}} />
+<div role="button" on:mouseup={() => {}} />
+