kandev/docs/plans/subtask-reparenting-drag-drop/task-02-frontend-nest-drop-infrastructure.md

id, title, status, wave, depends_on, plan, spec

id	title	status	wave	depends_on	plan	spec
02-frontend-nest-drop-infrastructure	Frontend nest-drop infrastructure	done	2	01-backend-composite-semantics	plan.md	../../specs/tasks/requirements/subtask-reparenting-drag-drop.md

Task 02: Frontend nest-drop infrastructure

Acceptance

• A single DndContext per sidebar group section replaces the per-level contexts, so a drag can target rows outside its own sibling level; sibling reorder behavior is unchanged.
• resolveSidebarDrop (pure) and computeNestTargets (pure) exist with unit tests; NestDropZone renders on candidate rows with data-testid="nest-drop-zone" and data-task-id.
• Existing TaskSwitcher / SortableTaskLevel tests pass (no behavior regression when no group-level context or reorder is configured).

Verification

cd apps/web && pnpm test -- components/task/task-switcher-subtask-dnd.test.ts components/task/task-switcher.test.tsx lib/sidebar/nest-candidates.test.ts
cd apps/web && pnpm run typecheck

Files likely touched

• apps/web/components/task/task-switcher-subtask-dnd.tsx — hoist DndContext out of SortableTaskLevel (new externalDragContext mode), add NestDropZone, resolveSidebarDrop, computeNestTargets, custom collision (pointerWithin → nest: ids, else closestCenter), sensors, group-level onDragStart/onDragEnd.
• apps/web/components/task/task-switcher.tsx — GroupSection renders the hoisted DndContext; TaskTreeContext carries candidate ids + onReparentTask; TaskTreeNode renders NestDropZone on candidate rows; new optional onReparentTask prop on TaskSwitcher (unwired for now).
• apps/web/components/task/task-switcher-subtask-dnd.test.ts (new) — resolveSidebarDrop unit tests: nest id mapping, group-root reorder, subtask-level reorder, cross-level drop → null, no-over → null.

Dependencies

Task 01 (semantics only — infra works against the existing updateTask path regardless).

Inputs

• Spec sections: What (gesture, targets, reorder preservation), Scenarios.
• Existing code: useLevelDnd / SortableTaskLevel / DraggableSortableTaskNode in task-switcher-subtask-dnd.tsx; TaskTreeLevel/GroupSection/TaskTreeContext in task-switcher.tsx; computeNestCandidates in apps/web/lib/sidebar/nest-candidates.ts; activation constraints constants.
• Reorder callbacks keep their signatures: onReorderGroup(orderedTaskIds), onReorderSubtasks(parentTaskId, orderedTaskIds).

Output contract

Report the component/helper changes, exact commands and results, files changed, blockers, residual risks; update this task and plan.md when acceptance passes.

Results

• cd apps/web && pnpm test -- components/task/task-switcher-subtask-dnd.test.ts components/task/task-switcher.test.tsx components/task/task-switcher-direct-subtasks.test.tsx — 31 passed (new helper tests + switcher regression suites).
• pnpm run typecheck clean; pnpm run lint clean (0 warnings); pnpm run i18n:ratchet clean.
• Hoisted per-level DndContext into TaskTreeDndGroup (one per group section; custom collision: pointerWithin → nest: ids win, else closestCenter); SortableTaskLevel gained externalDragContext; added NestDropZone + pure resolveSidebarDrop/computeNestTargets (unit-tested); GroupSection slimmed via props-object + new task-switcher-tree-context.ts (flattenGroupTasks/buildTaskTreeContext) to stay under lint line limits.
• Files changed: components/task/task-switcher-subtask-dnd.tsx, task-switcher-subtask-dnd.test.ts, task-switcher.tsx, task-switcher-tree-context.ts (new), src/locales/en/sidebar.json (sidebar:nestUnder).