$ show preactjs/signals
This is the official Preact Signals repository: a multi-package monorepo providing a high-performance reactive state management library. The core package (`@preact/signals-core`) implements fine-grained dependency tracking using a linked-list-based reactive graph, with primitives like `signal()`, `computed()`, `effect()`, `batch()`, `untracked()`, `createModel()`, and `action()`. Framework-specific integrations exist for Preact (`@preact/signals`) and React (`@preact/signals-react`), including hooks (`useSignal`, `useComputed`, `useSignalEffect`, `useModel`), utility components (`Show`, `For`), and automatic Babel transforms that inject `useSignals` for seamless reactive re-rendering. In addition to the core and framework libraries, the repository includes a comprehensive developer tooling ecosystem: an ESLint plugin with six rules to prevent common signal anti-patterns, a debug package (`@preact/signals-debug`) that instruments signal internals for logging and DevTools integration, a Vite plugin (`@preact/signals-agent-vite`) that wires up debug clients and Babel transforms, and a full-featured DevTools UI (`@preact/signals-devtools-ui`) with a timeline, performance insights, and an interactive dependency graph. A browser extension embeds this UI into Chrome DevTools, communicating via adapters that support direct, postMessage, and extension messaging patterns. The codebase is well-structured with clear separation of concerns, extensive test coverage (unit, integration, and cross-framework), and active maintenance. While certain components are tightly coupled to the signals ecosystem, several patterns (adapter-based communication, graph layout algorithm, batch reconciliation logic) are isolated enough for extraction into other projects. The repository uses modern tooling (pnpm workspaces, Vitest, Babel, ESLint/Oxlint) and keeps up with framework versions, indicating low technical drift.
The LLM identified 3 files worth highlighting for reuse:
A Preact component that renders the signal dependency graph using a custom layout algorithm: it topologically sorts nodes, applies barycenter heuristic for edge crossing minimization, and wraps dense layers into columns to avoid aspect ratio issues. The layout logic is self-contained (approx. 250 lines) and depends only on a few type definitions, making it extractable for any directed acyclic graph visualization task. It also includes features like search, collapse/expand, SVG export, and performance bailouts for large graphs.
An abstract base class and three concrete adapters (DirectAdapter, PostMessageAdapter, BrowserExtensionAdapter) that decouple the DevTools UI from the communication layer with the debug instrumentation. Each adapter implements a simple connect/disconnect/message transceive contract. The pattern allows the same UI to run in a browser extension panel, an iframe, or directly embedded in the application. The base adapter and its implementations are minimal and could be reused as a template for other cross-context messaging scenarios.
An ESLint rule that statically detects when a signal's `.value` is read inside a reactive scope behind a non-reactive guard (e.g., a plain variable or `.peek()`), which prevents the signal from being tracked as a dependency. It implements a custom analysis of reactive scopes (using call graphs and import resolution) and conditional branches. This logic is non-trivial and demonstrates deep understanding of the signals reactivity model. The rule infrastructure (scope utilities) is shared across all six rules and is designed for extensibility.