Re-work toHierarchy utility

Refactor `toHiearchy` to be more generic, performant

- Use callback to "pick" generic parent ID property instead of requiring that `pid` be hardcoded`
- Account for edge cases of an invalid parent ID
- Use Map to store node children for lookups
- Use one pass instead of removing empty nodes at the very end
- DX: use generics to type `toHierarchy`
- Make `toHierarchy` even more generic (reusable with `RecursiveList`)

Co-Authored-By: Bram <bramhavers@gmail.com>

types/TreeView/TreeView.svelte.d.ts

@@ -15,7 +15,7 @@ type $RestProps = SvelteHTMLElements["ul"];
 
 type $Props = {
   /**
-   * Provide a nested array of nodes to render
+   * Provide an array of nodes to render
    * @default []
    */
   nodes?: Array<TreeNode>;
@@ -94,11 +94,6 @@ export default class TreeView extends SvelteComponentTyped<
    */
   collapseAll: () => void;
 
-  /**
-   * Create a nested array from a flat array
-   */
-  toHierarchy: (flatArray: TreeNode[] & { pid?: any }[]) => TreeNode[];
-
   /**
    * Programmatically expand a subset of nodes.
    * Expands all nodes if no argument is provided

types/TreeView/index.d.ts

@@ -1,2 +1 @@
 export { default as TreeView } from "./TreeView.svelte";
-export { toHierarchy } from "./treeview";

types/TreeView/treeview.d.ts

@@ -1,9 +0,0 @@
-import { type TreeNode } from "./TreeView.svelte";
-/**
- * Create a nested array from a flat array
- */
-export function toHierarchy(
-  flatArray: TreeNode[] & { pid?: any }[],
-): TreeNode[];
-
-export default toHierarchy;

types/index.d.ts

@@ -143,7 +143,6 @@ export { default as TooltipFooter } from "./Tooltip/TooltipFooter.svelte";
 export { default as TooltipDefinition } from "./TooltipDefinition/TooltipDefinition.svelte";
 export { default as TooltipIcon } from "./TooltipIcon/TooltipIcon.svelte";
 export { default as TreeView } from "./TreeView/TreeView.svelte";
-export { default as toHierarchy } from "./TreeView/treeview";
 export { default as Truncate } from "./Truncate/Truncate.svelte";
 export { default as truncate } from "./Truncate/truncate";
 export { default as Header } from "./UIShell/Header.svelte";
@@ -167,3 +166,4 @@ export { default as SkipToContent } from "./UIShell/SkipToContent.svelte";
 export { default as HeaderGlobalAction } from "./UIShell/HeaderGlobalAction.svelte";
 export { default as HeaderSearch } from "./UIShell/HeaderSearch.svelte";
 export { default as UnorderedList } from "./UnorderedList/UnorderedList.svelte";
+export { default as toHierarchy } from "./utils/toHierarchy";

types/utils/toHierarchy.d.ts

@@ -0,0 +1,21 @@
+type NodeLike = {
+  id: string | number;
+  nodes?: NodeLike[];
+  [key: string]: any;
+};
+
+/** Create a hierarchical tree from a flat array. */
+export function toHierarchy<
+  T extends NodeLike,
+  K extends keyof Omit<T, "id" | "nodes">,
+>(
+  flatArray: T[] | readonly T[],
+  /**
+   * Function that returns the parent ID for a given node.
+   * @example
+   * toHierarchy(flatArray, (node) => node.parentId);
+   */
+  getParentId: (node: T) => T[K] | null,
+): (T & { nodes?: (T & { nodes?: T[] })[] })[];
+
+export default toHierarchy;