feat(Field): start implementing field api

.changeset/plenty-singers-matter.md

@@ -0,0 +1,6 @@
+---
+"@digdir/designsystemet-css": patch
+"@digdir/designsystemet-react": patch
+---
+
+Field: Adds `<Field>` component wrapping and connecting internal form elements for better accessibility

packages/css/field.css

@@ -0,0 +1,7 @@
+.ds-field {
+  display: contents;
+
+  & > * + * {
+    margin-top: var(--ds-spacing-2);
+  }
+}

packages/css/index.css

@@ -14,6 +14,7 @@
 @import url('./popover.css') layer(ds.components);
 @import url('./skiplink.css') layer(ds.components);
 @import url('./accordion.css') layer(ds.components);
+@import url('./field.css') layer(ds.components);
 @import url('./switch.css') layer(ds.components);
 @import url('./checkbox.css') layer(ds.components);
 @import url('./radio.css') layer(ds.components);

packages/react/src/components/ValidationMessage/ValidationMessage.tsx

@@ -30,10 +30,11 @@ export const ValidationMessage = forwardRef<
 
   return (
     <Component
-      ref={ref}
       className={cl('ds-validation-message', className)}
       data-error={error || undefined}
+      data-field='validation'
       data-size={size}
+      ref={ref}
       {...rest}
     />
   );

packages/react/src/components/form/Field/Field.mdx

@@ -0,0 +1,8 @@
+import { Meta, Controls, Primary } from '@storybook/blocks';
+
+import * as FieldStories from './Field.stories';
+
+<Meta of={FieldStories} />
+
+<Primary />
+<Controls />

packages/react/src/components/form/Field/Field.stories.tsx

@@ -0,0 +1,81 @@
+import type { Meta, StoryFn } from '@storybook/react';
+
+import { useEffect } from 'react';
+import { Label } from '../../Label';
+
+import { Field } from '.';
+import { ValidationMessage } from '../../ValidationMessage';
+import { Input } from '../Input';
+import { Select } from '../Select';
+import { Textarea } from '../Textarea';
+
+type Story = StoryFn<typeof Field>;
+
+export default {
+  title: 'Komponenter/Field',
+  component: Field,
+  argTypes: {
+    type: {
+      control: { type: 'radio' },
+      options: ['textarea', 'input', 'select', false],
+      mapping: { textarea: Textarea, input: Input, select: Select },
+    },
+  },
+} as Meta;
+
+// TMP toggles to test a11yField utility
+const toggles = {
+  type: 'textarea',
+  inputId: '',
+  label: true,
+  labelFor: '',
+  description: true,
+  descriptionId: '',
+  validation: true,
+  validationId: '',
+  moveToBody: false,
+};
+
+export const Preview: Story = (args) => {
+  const {
+    type,
+    inputId,
+    label,
+    labelFor,
+    description,
+    descriptionId,
+    validation,
+    validationId,
+    moveToBody,
+  } = args as typeof toggles;
+  const Component = type as keyof JSX.IntrinsicElements;
+
+  useEffect(() => {
+    const label = document.querySelector('label');
+    const valid = document.querySelector('[data-my-validation]');
+    const field = document.querySelector('[data-my-field]');
+    const root = moveToBody ? document.body : field;
+    if (valid && valid.parentElement !== root) root?.append(valid);
+    if (label && label.parentElement !== root) root?.prepend(label);
+  }, [moveToBody]);
+
+  return (
+    <Field data-my-field>
+      {label && <Label htmlFor={labelFor || undefined}>Kort beskrivelse</Label>}
+      {description && (
+        <Field.Description id={descriptionId || undefined}>
+          Beskrivelse
+        </Field.Description>
+      )}
+      {type && <Component id={inputId || undefined} />}
+      {validation && (
+        <ValidationMessage data-my-validation id={validationId || undefined}>
+          Feilmelding
+        </ValidationMessage>
+      )}
+    </Field>
+  );
+};
+
+// @ts-expect-error ts2559: Preview.args uses more properties for testing than what is supported by <Field>
+Preview.args = toggles;

packages/react/src/components/form/Field/Field.tsx

@@ -0,0 +1,19 @@
+import { useMergeRefs } from '@floating-ui/react';
+import cl from 'clsx/lite';
+import type { HTMLAttributes } from 'react';
+import { forwardRef, useEffect, useRef } from 'react';
+import { fieldObserver } from './fieldObserver';
+
+export type FieldProps = HTMLAttributes<HTMLDivElement>;
+export const Field = forwardRef<HTMLDivElement, FieldProps>(function Field(
+  { className, ...rest },
+  ref,
+) {
+  const fieldRef = useRef<HTMLDivElement>(null);
+  const mergedRefs = useMergeRefs([fieldRef, ref]);
+  useEffect(() => fieldObserver(fieldRef.current), []);
+
+  return (
+    <div className={cl('ds-field', className)} ref={mergedRefs} {...rest} />
+  );
+});

packages/react/src/components/form/Field/FieldDescription.tsx

@@ -0,0 +1,11 @@
+import type { HTMLAttributes } from 'react';
+import { forwardRef } from 'react';
+
+export type FieldDescriptionProps = HTMLAttributes<HTMLDivElement>;
+
+export const FieldDescription = forwardRef<
+  HTMLDivElement,
+  FieldDescriptionProps
+>(function FieldDescription(rest, ref) {
+  return <div data-field='description' ref={ref} {...rest} />;
+});

packages/react/src/components/form/Field/fieldObserver.test.tsx

@@ -0,0 +1,22 @@
+import { render, screen } from '@testing-library/react';
+import { vi } from 'vitest';
+
+import { Input, Label } from '../..';
+import { fieldObserver } from './fieldObserver';
+
+describe('fieldObserver', () => {
+  it('connects input and label', () => {
+    const { container } = render(
+      <div>
+        <Label>Navn</Label>
+        <Input />
+      </div>,
+    );
+    fieldObserver(container);
+
+    const label = screen.getByText('Navn');
+    const input = screen.getByLabelText('Navn');
+
+    expect(label).toHaveAttribute('for', input.id);
+  });
+});

packages/react/src/components/form/Field/fieldObserver.ts

@@ -0,0 +1,91 @@
+export function fieldObserver(fieldElement: HTMLElement | null) {
+  if (!fieldElement) return;
+
+  const elements = new Map<Element, string | null>();
+  const uuid = `:${Math.round(Date.now() + Math.random() * 100).toString(36)}`;
+  let input: Element | null = null;
+
+  const process = (mutations: Partial<MutationRecord>[]) => {
+    const changed: Node[] = [];
+    const removed: Node[] = [];
+
+    // Merge MutationRecords
+    for (const mutation of mutations) {
+      if (mutation.attributeName) changed.push(mutation.target ?? fieldElement);
+      changed.push(...(mutation.addedNodes || []));
+      removed.push(...(mutation.removedNodes || []));
+    }
+
+    // Register elements
+    for (const el of changed) {
+      if (!isElement(el)) continue;
+
+      if (isLabel(el)) elements.set(el, el.htmlFor);
+      else if (el.hasAttribute('data-field')) elements.set(el, el.id);
+      else if (isFormAssociated(el)) input = el;
+    }
+
+    // Reset removed elements
+    for (const el of removed) {
+      if (!isElement(el)) continue;
+
+      if (input === el) input = null;
+      if (elements.has(el)) {
+        setAttr(el, isLabel(el) ? 'for' : 'id', elements.get(el));
+        elements.delete(el);
+      }
+    }
+
+    // Connect elements
+    const inputId = input?.id || uuid;
+    const descs: string[] = [];
+    for (const [el, value] of elements) {
+      const desc = el.getAttribute('data-field');
+      const id = desc ? `${inputId}:${desc}` : inputId;
+
+      if (!value) setAttr(el, isLabel(el) ? 'for' : 'id', id); // Ensure we have a value
+      if (desc) descs[desc === 'validation' ? 'unshift' : 'push'](el.id); // Validations to the front
+    }
+
+    setAttr(input, 'id', inputId);
+    setAttr(input, 'aria-describedby', descs.join(' '));
+  };
+
+  const observer = createOptimizedMutationObserver(process);
+  observer.observe(fieldElement, {
+    attributeFilter: ['id', 'for', 'aria-describedby'],
+    attributes: true,
+    childList: true,
+    subtree: true,
+  });
+
+  process([{ addedNodes: fieldElement.querySelectorAll('*') }]); // Initial setup
+  observer.takeRecords(); // Clear initial setup queue
+  return () => observer.disconnect();
+}
+
+// Utilities
+const isElement = (node: Node) => node instanceof Element;
+const isLabel = (node: Node) => node instanceof HTMLLabelElement;
+const isFormAssociated = (node: Node): node is Element =>
+  'validity' in node && !(node instanceof HTMLButtonElement);
+
+const setAttr = (el: Element | null, name: string, value?: string | null) =>
+  value ? el?.setAttribute(name, value) : el?.removeAttribute(name);
+
+// Speed up MutationObserver by debouncing, clearing internal queue after changes and only running when page is visible
+function createOptimizedMutationObserver(callback: MutationCallback) {
+  const queue: MutationRecord[] = [];
+  const observer = new MutationObserver((mutations) => {
+    if (!queue.length) requestAnimationFrame(process);
+    queue.push(...mutations);
+  });
+
+  const process = () => {
+    callback(queue, observer);
+    queue.length = 0; // Reset queue
+    observer.takeRecords(); // Clear queue due to DOM changes in callback
+  };
+
+  return observer;
+}

packages/react/src/components/form/Field/index.ts

@@ -0,0 +1,21 @@
+import { Field as FieldParent } from './Field';
+import { FieldDescription } from './FieldDescription';
+
+/**
+ * @example
+ * <Field>
+ *  <Label>Label text</Label>
+ *  <Field.Description>Description</Field.Description>
+ *  <Input />
+ *  <ValidationMessage>Validation message</ValidationMessage>
+ * </Field>
+ */
+const Field = Object.assign(FieldParent, {
+  Description: FieldDescription,
+});
+
+Field.Description.displayName = 'Field.Description';
+
+export type { FieldProps } from './Field';
+export type { FieldDescriptionProps } from './FieldDescription';
+export { Field, FieldDescription };

packages/react/src/components/index.ts

@@ -19,6 +19,7 @@ export * from './Chip';
 export * from './Pagination';
 export * from './SkipLink';
 export * from './Tooltip';
+export * from './form/Field';
 export * from './form/Checkbox';
 export * from './form/Radio';
 export * from './form/Fieldset';