chore: import upstream snapshot with attribution

js/dataframe/shared/tanstack/index.ts

@@ -0,0 +1,23 @@
+export { createSvelteTable } from "./table.svelte.js";
+
+export { createSvelteVirtualizer, type VirtualItem } from "./virtual.svelte.js";
+
+export {
+	createColumnHelper,
+	getCoreRowModel,
+	getSortedRowModel,
+	getFilteredRowModel,
+	type ColumnDef,
+	type TableOptions,
+	type Table,
+	type Header,
+	type Cell,
+	type Row,
+	type SortingState,
+	type ColumnFiltersState,
+	type ColumnPinningState,
+	type FilterFn,
+	type SortingFn,
+	type CellContext,
+	type HeaderContext
+} from "@tanstack/table-core";

js/dataframe/shared/tanstack/table.svelte.ts

@@ -0,0 +1,121 @@
+import {
+	createTable,
+	type RowData,
+	type TableOptions,
+	type TableOptionsResolved,
+	type TableState
+} from "@tanstack/table-core";
+
+/**
+ * Merges objects while preserving property getters for lazy evaluation.
+ * Properties are defined as getters that look up values from sources in
+ * reverse order at access time. This is critical: it means reading a
+ * property from the merged result doesn't happen until the property is
+ * actually accessed, not when mergeObjects is called.
+ */
+export function mergeObjects(...sources: any): any {
+	const target: Record<string, any> = {};
+	for (let i = 0; i < sources.length; i++) {
+		let source = sources[i];
+		if (typeof source === "function") source = source();
+		if (source) {
+			const descriptors = Object.getOwnPropertyDescriptors(source);
+			for (const key in descriptors) {
+				if (key in target) continue;
+				Object.defineProperty(target, key, {
+					enumerable: true,
+					get() {
+						for (let j = sources.length - 1; j >= 0; j--) {
+							let s = sources[j];
+							if (typeof s === "function") s = s();
+							const v = (s || {})[key];
+							if (v !== undefined) return v;
+						}
+					}
+				});
+			}
+		}
+	}
+	return target;
+}
+
+/**
+ * Creates a reactive TanStack Table for Svelte 5.
+ *
+ * The reactivity works through mergeObjects' lazy getters:
+ * - $effect.pre calls table.setOptions() with a merged object
+ * - The merged object has lazy getters for `data`, `columns`, `state`, etc.
+ * - TanStack stores this object but doesn't deep-read all properties immediately
+ * - When getRowModel() is called (in $derived), TanStack reads `data` and `columns`
+ *   through the lazy getters, which read the reactive $state/$derived values
+ * - onStateChange fires when TanStack mutates its own state → bumps version
+ * - version is read by getRowModel/getHeaderGroups → $derived re-evaluates
+ */
+export function createSvelteTable<TData extends RowData>(
+	options: TableOptions<TData>
+) {
+	const resolvedOptions: TableOptionsResolved<TData> = mergeObjects(
+		{
+			state: {},
+			onStateChange() {},
+			renderFallbackValue: null,
+			mergeOptions: (
+				defaultOptions: TableOptions<TData>,
+				opts: Partial<TableOptions<TData>>
+			) => {
+				return mergeObjects(defaultOptions, opts);
+			}
+		},
+		options
+	);
+
+	const table = createTable(resolvedOptions);
+	let state = $state<Partial<TableState>>(table.initialState);
+	let version = $state(0);
+
+	function updateOptions(): void {
+		table.setOptions(() => {
+			// Always merge from resolvedOptions instead of prev to prevent
+			// unbounded getter chains. Using prev would add a new mergeObjects
+			// layer on every call; properties not in the overrides would have
+			// to traverse every previous layer, causing stack overflow.
+			// TanStack's setOptions already re-applies feature defaults via
+			// mergeOptions, so we don't lose any internal defaults.
+			return mergeObjects(resolvedOptions, options, {
+				state: mergeObjects(state, options.state || {}),
+				onStateChange: (updater: any) => {
+					if (updater instanceof Function) state = updater(state);
+					else state = mergeObjects(state, updater);
+					version += 1;
+					options.onStateChange?.(updater);
+				}
+			});
+		});
+	}
+
+	// Initial sync
+	updateOptions();
+
+	// Re-sync when options change. Because mergeObjects uses lazy getters,
+	// this effect's tracked dependencies are only the properties that
+	// table.setOptions() eagerly reads (which is minimal — mostly just
+	// checking if the options object reference changed).
+	$effect.pre(() => {
+		updateOptions();
+	});
+
+	return {
+		getRowModel: () => {
+			void version;
+			return table.getRowModel();
+		},
+		getHeaderGroups: () => {
+			void version;
+			return table.getHeaderGroups();
+		},
+		getColumn: (id: string) => {
+			void version;
+			return table.getColumn(id);
+		}
+	};
+}

js/dataframe/shared/tanstack/virtual.svelte.ts

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+import {
+	Virtualizer,
+	elementScroll,
+	observeElementOffset,
+	observeElementRect,
+	type PartialKeys,
+	type VirtualizerOptions
+} from "@tanstack/virtual-core";
+import { untrack } from "svelte";
+
+export type { VirtualItem } from "@tanstack/virtual-core";
+
+/**
+ * Creates a reactive TanStack Virtualizer for Svelte 5.
+ *
+ * Returns a getter function that returns the virtualizer instance.
+ * Call the getter inside $derived or template expressions to create
+ * reactive dependencies on the virtualizer state.
+ */
+export function createSvelteVirtualizer<
+	TScrollElement extends Element,
+	TItemElement extends Element
+>(
+	options: PartialKeys<
+		VirtualizerOptions<TScrollElement, TItemElement>,
+		"observeElementRect" | "observeElementOffset" | "scrollToFn"
+	>
+): {
+	instance: Virtualizer<TScrollElement, TItemElement>;
+	virtualItems: () => ReturnType<
+		Virtualizer<TScrollElement, TItemElement>["getVirtualItems"]
+	>;
+	totalSize: () => number;
+} {
+	let version = $state(0);
+
+	const virtualizer = new Virtualizer<TScrollElement, TItemElement>({
+		observeElementRect: observeElementRect,
+		observeElementOffset: observeElementOffset,
+		scrollToFn: elementScroll,
+		...options,
+		onChange: (instance, sync) => {
+			if (sync) {
+				version += 1;
+			} else {
+				queueMicrotask(() => {
+					version += 1;
+				});
+			}
+			options.onChange?.(instance, sync);
+		}
+	});
+
+	$effect(() => {
+		const cleanup = virtualizer._didMount();
+		untrack(() => {
+			version += 1;
+		});
+		return cleanup;
+	});
+
+	let prev_count = 0;
+
+	$effect(() => {
+		const current_count = options.count;
+		virtualizer.setOptions({
+			observeElementRect: observeElementRect,
+			observeElementOffset: observeElementOffset,
+			scrollToFn: elementScroll,
+			...options,
+			onChange: (instance, sync) => {
+				if (sync) {
+					version += 1;
+				} else {
+					queueMicrotask(() => {
+						version += 1;
+					});
+				}
+				options.onChange?.(instance, sync);
+			}
+		});
+
+		if (prev_count === 0 && current_count > 0) {
+			virtualizer.measure();
+		}
+		prev_count = current_count;
+	});
+
+	$effect.pre(() => {
+		void version;
+		virtualizer._willUpdate();
+	});
+
+	return {
+		instance: virtualizer,
+		virtualItems: () => {
+			void version;
+			return virtualizer.getVirtualItems();
+		},
+		totalSize: () => {
+			void version;
+			return virtualizer.getTotalSize();
+		}
+	};
+}