Designing Async-First Signals

About this video

• Video Title: Designing Async-First Signals
• Channel: Ryan Carniato
• Speakers: Ryan Carniato
• Duration: 06:30:27

Overview

This video discusses the design principles and implementation of async-first signals in modern UI frameworks, with a particular focus on SolidJS. Ryan Carniato explores concepts like suspense, transitions, optimistic UI, and tearing, comparing Solid's approach with those in React and Svelte. He delves into the challenges of managing asynchronous operations within reactive systems, the importance of consistency guarantees, and the potential benefits of an async-first design for improved developer experience and performance. The discussion also touches upon the evolution of reactivity, the role of compilers, and the impact of different data models on performance.

Key takeaways

• Async Handling in JS Frameworks: JavaScript's single-threaded nature and its unique approach to concurrency (schedulers, not threads) influenced early UI framework designs, often overlooking explicit async management.
• Reactivity and Consistency: Signals and reactive frameworks like React prioritize UI consistency to build user trust, which is crucial for a good user experience.
• Suspense and Transitions: React's Suspense and Transitions APIs, which inspired Solid's implementations, aim to manage loading states and smooth UI updates during asynchronous operations. Suspense provides layout-driven loading boundaries, while transitions offer "holding" models to maintain previous UI states.
• Async Modes: Four async modes are discussed: placeholder (Suspense), hold (transitions), optimistic UI, and tearing (default behavior without specific handling).
• Tearing and Trust: Tearing, where parts of the UI update asynchronously, can break user trust if not handled carefully, highlighting the need for consistent rendering.
• Svelte's Approach: Svelte's async handling, particularly its derived async and holding model, is examined, with comparisons made to Solid's methods, noting the compiler's role in dependency inference.
• Async in Routing and Actions: The integration of async operations in routers and server actions (like in Remix) is crucial for modern web applications, impacting how routes and data are fetched and displayed.
• Signals vs. Observables: Signals are presented as a mechanism for synchronization guarantees, contrasting with RxJS, which is viewed as an event system.
• The "Cost of Consistency": Different frameworks (React, Vue, Svelte, Solid) report values differently, and introducing async operations can break assumptions about derived values, leading to potential bugs if not managed correctly.
• Async-First Design Thought Experiment (R3): The speaker proposes an async-first approach where transitions are implicit, and tearing is an opt-out, aiming for a more unified API for managing async states.
• IsPending as a Graph Concept: The isPending concept is reframed as a graph-level question rather than a per-signal flag, allowing for more comprehensive state management.
• Deferred Commits and Disposal: The idea of deferring pure disposal of components and nodes in the graph, rather than immediate disposal, is explored as a way to manage transitions and maintain UI responsiveness without explicit forking.
• Pure Memos vs. Render Effects: A distinction is made between pure memoized computations and render effects, with the latter being handled specially to manage asynchronous updates and UI stability.
• The Challenge of Composition: Creating reusable components that seamlessly handle async operations and transitions is a significant challenge, often requiring careful consideration of state management and component lifecycles.
• Signals and Performance: While signals offer fine-grained reactivity, their performance in complex scenarios, especially with large state trees or frequent updates, requires careful management and optimization.
• The Importance of the Reactive Graph: The underlying reactive graph is key to Solid's approach, enabling features like automatic disposal and efficient propagation of changes, which is contrasted with compiler-driven optimizations in other frameworks.
• External Stores vs. Internal Signals: The discussion highlights the debate around using external state management solutions versus internal signals, with a leaning towards the benefits of signals for integrated reactivity within the framework.
• The "Outside vs. Inside" System Concept: A key realization is the distinction between operations happening "inside" the reactive system (seamless) and "outside" (messy, requiring careful handling), particularly concerning event handlers and effects.
• React Compiler's Role: The React compiler aims to optimize performance by automatically memoizing components and managing state updates, addressing some of the challenges inherent in React's model, especially when dealing with context-based state.
• The Future of React: The speaker speculates that React's future might involve a shift towards isolating state from rendering and potentially adopting a more signals-like approach, even if not explicitly labeled as such.
• Benchmarks and Real-World Performance: The video emphasizes the limitations of synthetic benchmarks and the importance of testing in real-world scenarios, noting that optimized prototypes may not always reflect production performance.
• The Role of Funding: The discussion touches upon the impact of funding from companies like Google and Versel on the development of foundational technologies in the JavaScript ecosystem, benefiting frameworks like Solid.
• This Week in JavaScript: The video concludes with a rapid-fire summary of recent JavaScript ecosystem news, including Solid's growth, the adoption of Solid in tooling, the development of Solid Start, and commentary on HTMX and the overuse of useEffect.