nvim-tree/nvim-tree.lua is a mature Neovim file explorer plugin written entirely in Lua. It provides a tree-view sidebar with file system operations, git status indicators, diagnostic integration (LSP/COC), file filtering, bookmarks, clipboard management, and extensive customization. The architecture is modular, with clearly separated concerns: an explorer module handles tree construction and traversal; a view module manages the floating or split window; a renderer with a decorator pattern applies icons and highlights; a git module runs async git status queries; and an actions layer handles file create/rename/delete/trash. It uses an internal event system, filesystem watchers via libuv, and a public API for user extensions. The codebase demonstrates solid Lua craftsmanship, including a fluent node iterator, a classic OOP library, and a config validation recursive checker. It is actively maintained, with continuous adaptation to Neovim API changes and cross-platform support.
django-mptt-admin is a reusable Django application that provides an interactive tree view interface in the Django admin for models using django-mptt (Modified Preorder Tree Traversal). It enables drag-and-drop reordering, inline editing, adding child nodes, filtering within subtrees, and a grid view alternative. The backend is implemented as a Django admin mixin (`DjangoMpttAdminMixin`) that handles tree JSON serialization, move operations, and changelist customization. The frontend is a TypeScript integration layer that initializes a tree widget (using the tree-element library) and manages CSRF-protected AJAX move requests, loading spinners, and error handling. The repository includes a full example project with tests (unit, view, and Playwright), CI/CD pipelines, and internationalization for multiple languages. It is actively maintained, with recent major version 3.0.0 that replaced the previous jqTree library with a modern jQuery-free tree widget.
react-sortable-tree is a React component library that provides a drag-and-drop sortable tree view for hierarchical data. It renders nested arrays of nodes with expand/collapse, virtualization via react-virtualized, search with highlighting, theming, and extensive callback hooks for move and visibility changes. The library is not actively maintained; the last release was in 2020, and the README explicitly disclaims maintenance. The codebase is well-architected with clean separation of concerns: pure tree-data utility functions (walk, map, insertNode, etc.) separated from React rendering, a DndManager class that wraps react-dnd, and a theming system. Despite its staleness, the core tree manipulation algorithms are high-quality and extractable for other projects. The library depends on outdated versions of React (16) and react-dnd (11), and uses react-virtualized instead of the more modern react-window.