# TreeView

> Application tree with hierarchical selection, expansion, roving focus, and arrow-key navigation.

- Status: beta
- Group: navigation
- Page: https://www.digitaltableteur.com/design-system/components/tree-view
- Contract: https://www.digitaltableteur.com/contracts/v1/TreeView.contract.json

## When to use

Use TreeView for application hierarchies that users expand, collapse, navigate, and select. Use stable identifiers and concise node labels.

## When not to use

- Do not replace a sitemap or ordinary nested navigation list.
- Do not nest independently focusable controls inside node labels.
- Do not use TreeView for a flat set of links or ordinary site navigation.

## Look-alikes

The contract names no look-alike with a deciding condition.

## Props

| Prop | Type | Default | Description | Required |
| --- | --- | --- | --- | --- |
| `nodes` | `TreeViewNode[]` | none | Hierarchical nodes. | Yes |
| `aria-label` | `string` | none | Accessible name for the tree. | Yes |
| `selectedId` | `string \| null` | none | Controlled selected node identifier. | No |
| `defaultSelectedId` | `string \| null` | `null` | Initial uncontrolled selected node identifier. | No |
| `onSelectedIdChange` | `(id: string) => void` | none | Receives selection changes. | No |
| `expandedIds` | `string[]` | none | Controlled expanded node identifiers. | No |
| `defaultExpandedIds` | `string[]` | `[]` | Initial uncontrolled expanded node identifiers. | No |
| `onExpandedIdsChange` | `(ids: string[]) => void` | none | Receives expansion changes. | No |
| `size` | `"sm" \| "md" \| "lg"` | `md` | Density scale. | No |
| `className` | `string` | none | No description in the contract. | No |

## Variants

- Available sizes: `sm`, `md`, `lg` (default `md`).

## Invalid combinations

- MUST NOT: `selectedId` and `defaultSelectedId` set together. `selectedId` makes the component controlled and `defaultSelectedId` uncontrolled; pass one, not both.
- MUST NOT: `expandedIds` and `defaultExpandedIds` set together. `expandedIds` makes the component controlled and `defaultExpandedIds` uncontrolled; pass one, not both.

## Keyboard

| Key | Behaviour |
| --- | --- |
| ArrowUp | Moves focus or the value in that direction. (standard) |
| ArrowDown | Moves focus or the value in that direction. (standard) |
| ArrowLeft | Moves focus or the value in that direction. (standard) |
| ArrowRight | Moves focus or the value in that direction. (standard) |
| Home | Moves to the first item. (standard) |
| End | Moves to the last item. (standard) |
| Enter | Activates the focused control. (standard) |
| Space | Activates or toggles the focused control. (standard) |

Rows marked (standard) name a key the contract lists without a description; the behaviour shown is the usual one for that key.

## Rules

Every item under When not to use is a MUST NOT. MUST and SHOULD follow RFC 2119.

| Level | Rule | How it is checked |
| --- | --- | --- |
| MUST NOT | `selectedId` and `defaultSelectedId` set together. `selectedId` makes the component controlled and `defaultSelectedId` uncontrolled; pass one, not both. | Checked by the MCP tool validate_component_usage. |
| MUST NOT | `expandedIds` and `defaultExpandedIds` set together. `expandedIds` makes the component controlled and `defaultExpandedIds` uncontrolled; pass one, not both. | Checked by the MCP tool validate_component_usage. |
| MUST | ARIA: Root has role=tree and an accessible name. | Not yet verified: no evidence record. WCAG 4.1.2. |
| MUST | ARIA: Nodes expose role=treeitem, aria-level and aria-selected. | Not yet verified: no evidence record. WCAG 4.1.2. |
| MUST | ARIA: Branch nodes expose aria-expanded. | Not yet verified: no evidence record. WCAG 4.1.2. |
| MUST | ARIA: Only the focused treeitem has tabIndex=0. | Not yet verified: no evidence record. WCAG 4.1.2. |
| MUST | Required stories produce no axe violations at the configured severity. | Automated by `npm run test:stories:matrix:ci`. WCAG 2.5.8. |
| MUST | The accessibility tree (role, name, state) matches the committed snapshot for every required story. | Automated by `npm run test:stories:matrix:ci`. WCAG 1.3.1, 4.1.2. |
| MUST | The component remains legible and operable under a real browser forced-colors: active pass. | Automated by `npm run test:stories:hc`. |
| MUST | Every documented keyboard interaction works as specified. | Not yet verified: no evidence record. WCAG 2.1.1, 2.1.2. |
| MUST | A human completed an end-to-end accessibility review of this component. | Manual review, last on 2026-07-26. |
| SHOULD | Give the tree an accessible label that identifies the hierarchy. | Not stated in the contract. |
| SHOULD | Use stable node identifiers across filtering, refreshes, and reordering. | Not stated in the contract. |
| SHOULD | Keep labels concise and place secondary status in the description. | Not stated in the contract. |
| SHOULD | Preserve expansion state when nearby application content changes. | Not stated in the contract. |
| SHOULD NOT | Do not embed buttons, inputs, or menus inside a tree item's label. | Not stated in the contract. |

## Install and import

- Install: `npm install @digitaltableteur/react` (version 0.9.1, restricted access on npm).
- Import: `import { TreeView } from "@digitaltableteur/react";`
- Entry point: `@digitaltableteur/react/navigation` exports it too.
- Styles: import `@digitaltableteur/react/style.css` once at the app boundary.

## Links

- Machine-readable contract (Design System Contract 1.0): https://www.digitaltableteur.com/contracts/v1/TreeView.contract.json
- Markdown version of this page: https://www.digitaltableteur.com/design-system/components/tree-view.md
- Component index as JSON: https://www.digitaltableteur.com/design-system/components.json
- All components: https://www.digitaltableteur.com/design-system/components
- Source: The implementation lives in a private repository. This page, its Markdown twin and the contract are generated from it at build time and are the public source of truth.