Accessibility Round 2

src/form/README.md

@@ -33,7 +33,7 @@ form.resetValidation();
 ```html
 <tp-form prevent-submit="yes">
 	<form action="#">
-		<tp-form-field required="yes" revalidate-on-change="no"> <-- If you don't want to revalidate as the value changes
+		<tp-form-field required="yes" revalidate-on-change="no"> <!-- If you don't want to revalidate as the value changes -->
 			<label>Field 1</label>
 			<input type="text" name="field_1">
 		</tp-form-field>
@@ -55,7 +55,7 @@ form.resetValidation();
 			<textarea name="field_4"></textarea>
 		</tp-form-field>
 		<tp-form-submit submitting-text="Submitting...">
-			<button type="submit">Submit</button> <-- There must be a submit button inside this component
+			<button type="submit">Submit</button> <!-- There must be a submit button inside this component -->
 		</tp-form-submit>
 	</form>
 </tp-form>
@@ -84,3 +84,142 @@ Validates the form.
 ### `resetValidation`
 
 Removes all validation errors from the form.
+
+## Error Summary
+
+For accessible form validation, you can add an error summary that lists all validation errors with links to the invalid fields. This follows the [GOV.UK design system pattern](https://design-system.service.gov.uk/components/error-summary/).
+
+The component provides maximum flexibility — you control the markup structure.
+
+```html
+<tp-form prevent-submit="yes">
+	<form action="#">
+		<tp-form-errors>
+			<p><tp-form-errors-heading format="$count error(s) found"></tp-form-errors-heading></p>
+			<tp-form-errors-list role="list"></tp-form-errors-list>
+		</tp-form-errors>
+		<!-- form fields here -->
+	</form>
+</tp-form>
+```
+
+### Components
+
+| Component | Purpose |
+|-----------|---------|
+| `tp-form-errors` | Container. Sets `active="yes"` when errors exist. |
+| `tp-form-errors-heading` | Displays error count. Use `format` attribute with `$count` placeholder. |
+| `tp-form-errors-list` | Contains the list of error links. Add `role="list"` for accessibility. |
+| `tp-form-errors-error` | Generated for each error. Has `role="listitem"` auto-applied. |
+
+### Visibility
+
+The error summary is hidden by default. Use CSS to show it when `active="yes"`:
+
+```css
+tp-form-errors {
+	display: none;
+}
+
+tp-form-errors[active="yes"] {
+	display: block;
+}
+```
+
+### Numbering with CSS Counters
+
+Use CSS counters to number the error list:
+
+```css
+tp-form-errors-list {
+	counter-reset: errors;
+}
+
+tp-form-errors-error {
+	display: block;
+	counter-increment: errors;
+}
+
+tp-form-errors-error::before {
+	content: counter(errors) ". ";
+}
+```
+
+### Focus Management
+
+- If `tp-form-errors` exists: Focus moves to the error summary on validation failure
+- If `tp-form-errors` doesn't exist: Focus moves to the first visible invalid field
+
+## Accessibility
+
+The form component provides accessibility features while you control the semantic markup.
+
+### What the Component Handles
+
+- **Auto-generates IDs** on form fields if not present
+- **Auto-sets `for` attribute** on labels if not present
+- **`aria-invalid`** on fields when validation fails
+- **`aria-describedby`** linking fields to error messages
+- **`role="alert"`** on dynamically created error messages
+- **`role="listitem"`** on error summary list items
+- **Focus management** to error summary or first visible invalid field
+
+### What You Should Provide
+
+| Attribute | Purpose |
+|-----------|---------|
+| `aria-required="true"` | On required inputs for screen reader announcements |
+| `role="list"` | On `tp-form-errors-list` for proper list semantics |
+
+## Internationalization (i18n)
+
+### Inline Error Messages
+
+Customize inline error messages via `window.tpFormErrors`:
+
+```js
+window.tpFormErrors['required'] = 'Ce champ est obligatoire';
+window.tpFormErrors['email'] = 'Veuillez entrer une adresse email valide';
+```
+
+### Summary Error Messages
+
+Customize summary error messages via `window.tpFormSummaryErrors`. Use `%label%` as a placeholder for the field label:
+
+```js
+window.tpFormSummaryErrors['required'] = '%label% est obligatoire';
+window.tpFormSummaryErrors['email'] = '%label%: Veuillez entrer une adresse email valide';
+```
+
+### Built-in Validators
+
+| Validator | Default Error Message | Default Summary Message |
+|-----------|----------------------|-------------------------|
+| `required` | This field is required | %label% is required |
+| `email` | Please enter a valid email address | %label%: Please enter a valid email address |
+| `min-length` | Must be at least %1 characters | %label%: Must be at least %1 characters |
+| `max-length` | Must be less than %1 characters | %label%: Must be less than %1 characters |
+| `no-empty-spaces` | This field should not contain only white-spaces | %label%: Should not contain only white-spaces |
+| `zip` | Please enter a valid zip code | %label%: Please enter a valid zip code |
+
+## Custom Validators
+
+Add custom validators to `window.tpFormValidators`:
+
+```js
+window.tpFormValidators['my-validator'] = {
+	validate: (field) => {
+		// validation logic
+		return true;
+	},
+	// Inline error message (shown next to field)
+	getErrorMessage: (field) => 'This field is invalid',
+	// Summary error message (shown in error summary, optional)
+	getSummaryMessage: (field) => {
+		const label = field.querySelector('label')?.textContent || 'Field';
+		return `${label} is invalid`;
+	},
+};
+```
+
+If `getSummaryMessage` is not defined, the component falls back to `getErrorMessage`.

src/form/definitions.d.ts

@@ -10,6 +10,7 @@ export interface TPFormValidator {
 	validate: { ( field: TPFormFieldElement ): boolean | Promise<boolean> };
 	getErrorMessage: { ( field: TPFormFieldElement ): string };
 	getSuspenseMessage?: { ( field: TPFormFieldElement ): string };
+	getSummaryMessage?: { ( field: TPFormFieldElement ): string };
 }
 
 /**
@@ -24,6 +25,9 @@ declare global {
 		tpFormErrors: {
 			[ key: string ]: string;
 		};
+		tpFormSummaryErrors: {
+			[ key: string ]: string;
+		};
 		tpFormSuspenseMessages: {
 			[ key: string ]: string;
 		};

src/form/index.html

@@ -28,6 +28,44 @@
 		textarea {
 			width: 100%;
 		}
+
+		/* Error summary - hidden by default, shown when active */
+		tp-form-errors {
+			display: none;
+		}
+
+		tp-form-errors[active="yes"] {
+			display: block;
+			background: #fef2f2;
+			border: 1px solid #ef4444;
+			border-radius: 4px;
+			padding: 16px;
+			margin-bottom: 16px;
+		}
+
+		tp-form-errors[active="yes"] p {
+			color: #dc2626;
+			font-size: 1rem;
+			font-weight: bold;
+			margin: 0 0 8px 0;
+		}
+
+		tp-form-errors-list {
+			counter-reset: errors;
+		}
+
+		tp-form-errors-error {
+			display: block;
+			counter-increment: errors;
+		}
+
+		tp-form-errors-error::before {
+			content: counter(errors) ". ";
+		}
+
+		tp-form-errors[active="yes"] a {
+			color: #dc2626;
+		}
 	</style>
 
 	<script type="module">
@@ -48,7 +86,11 @@
 	<main>
 		<tp-form prevent-submit="yes">
 			<form action="#">
-				<h3>Synchronous Form</h3>
+				<h3>Synchronous Form (with visible error summary)</h3>
+				<tp-form-errors>
+					<p><tp-form-errors-heading format="$count error(s) found in the form"></tp-form-errors-heading></p>
+					<tp-form-errors-list role="list"></tp-form-errors-list>
+				</tp-form-errors>
 				<tp-form-field no-empty-spaces="yes" required="yes">
 					<label>Field 1</label>
 					<input type="text" name="field_1">

src/form/index.ts

@@ -31,15 +31,21 @@ const validators = [
  */
 window.tpFormValidators = {};
 window.tpFormErrors = {};
+window.tpFormSummaryErrors = {};
 window.tpFormSuspenseMessages = {};
 
 // Register validators.
 validators.forEach( (
-	{ name, validator, errorMessage }: { name: string, validator: TPFormValidator, errorMessage: string }
+	{ name, validator, errorMessage, summaryErrorMessage }: { name: string, validator: TPFormValidator, errorMessage: string, summaryErrorMessage?: string }
 ): void => {
 	// Assigning validators and error messages to various fields.
 	window.tpFormValidators[ name ] = validator;
 	window.tpFormErrors[ name ] = errorMessage;
+
+	// Register summary error message if provided.
+	if ( summaryErrorMessage ) {
+		window.tpFormSummaryErrors[ name ] = summaryErrorMessage;
+	}
 } );
 
 /**
@@ -48,6 +54,10 @@ validators.forEach( (
 import { TPFormElement } from './tp-form';
 import { TPFormFieldElement } from './tp-form-field';
 import { TPFormErrorElement } from './tp-form-error';
+import { TPFormErrorsElement } from './tp-form-errors';
+import { TPFormErrorsHeadingElement } from './tp-form-errors-heading';
+import { TPFormErrorsListElement } from './tp-form-errors-list';
+import { TPFormErrorsErrorElement } from './tp-form-errors-error';
 import { TPFormSuspenseElement } from './tp-form-suspense';
 import { TPFormSubmitElement } from './tp-form-submit';
 
@@ -57,5 +67,9 @@ import { TPFormSubmitElement } from './tp-form-submit';
 customElements.define( 'tp-form', TPFormElement );
 customElements.define( 'tp-form-field', TPFormFieldElement );
 customElements.define( 'tp-form-error', TPFormErrorElement );
+customElements.define( 'tp-form-errors', TPFormErrorsElement );
+customElements.define( 'tp-form-errors-heading', TPFormErrorsHeadingElement );
+customElements.define( 'tp-form-errors-list', TPFormErrorsListElement );
+customElements.define( 'tp-form-errors-error', TPFormErrorsErrorElement );
 customElements.define( 'tp-form-suspense', TPFormSuspenseElement );
 customElements.define( 'tp-form-submit', TPFormSubmitElement );

src/form/tp-form-errors-error.ts

@@ -0,0 +1,45 @@
+/**
+ * TP Form Errors Error.
+ */
+export class TPFormErrorsErrorElement extends HTMLElement {
+	/**
+	 * Constructor.
+	 */
+	constructor() {
+		// Initialize parent.
+		super();
+
+		// Use event delegation to handle clicks on dynamically added anchors.
+		this.addEventListener( 'click', this.handleClick.bind( this ) );
+	}
+
+	/**
+	 * Handle click on error link.
+	 *
+	 * @param {Event} event Click event.
+	 */
+	protected handleClick( event: Event ): void {
+		// Find the anchor element.
+		const target = event.target as HTMLElement;
+		const anchor = target.closest( 'a' );
+
+		// Only handle clicks on anchors.
+		if ( ! anchor ) {
+			// Bail early.
+			return;
+		}
+
+		// Prevent default to avoid hash in URL.
+		event.preventDefault();
+
+		// Get the field ID from href.
+		const href = anchor.getAttribute( 'href' ) ?? '';
+		const fieldId = href.replace( '#', '' );
+
+		// Focus the target field.
+		if ( fieldId ) {
+			const targetField = document.getElementById( fieldId );
+			targetField?.focus();
+		}
+	}
+}

src/form/tp-form-errors-heading.ts

@@ -0,0 +1,36 @@
+/**
+ * TP Form Errors Heading.
+ *
+ * Displays the error count. User controls the heading element wrapper.
+ */
+export class TPFormErrorsHeadingElement extends HTMLElement {
+	/**
+	 * Get format.
+	 *
+	 * @return {string} Format with $count placeholder.
+	 */
+	get format(): string {
+		// Get format.
+		return this.getAttribute( 'format' ) ?? '';
+	}
+
+	/**
+	 * Set format.
+	 *
+	 * @param {string} format Format string.
+	 */
+	set format( format: string ) {
+		// Set format.
+		this.setAttribute( 'format', format );
+	}
+
+	/**
+	 * Update the heading with the error count.
+	 *
+	 * @param {number} count Number of errors.
+	 */
+	update( count: number ): void {
+		// Update count.
+		this.textContent = this.format.replace( '$count', count.toString() );
+	}
+}