next.js

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The Next.js repository is a comprehensive framework for building modern, server-rendered React applications. It provides a robust set of tools and utilities that simplify the development, deployment, and optimization of web applications. The key functionality of the Next.js framework can be broadly categorized into three main areas: server-side rendering, client-side routing, and the build process.

The server-side rendering functionality, located in the …/server directory, is responsible for rendering React components on the server and generating the initial HTML response. This includes handling API routes, managing the incremental cache, and providing error handling mechanisms. The renderToHTMLOrFlightImpl() function in the …/app-render.tsx file is the main entry point for the server-side rendering process, coordinating the various components and utilities involved.

The client-side routing functionality, found in the …/client directory, manages the navigation, prefetching, and server actions on the client-side. The Router component in the app-router.tsx file is the core of the client-side routing system, handling the navigation and rendering of the application's components.

The build process, encapsulated in the …/build directory, is responsible for generating the production-ready assets for a Next.js application. This includes managing the Webpack configuration, handling external dependencies, and generating build manifests. The getBaseWebpackConfig() function in the …/webpack-config.ts file is the main entry point for the build process, creating the necessary Webpack configurations based on the provided options.

Throughout the codebase, Next.js leverages several key technologies and design choices to achieve its goals:

• Webpack: Next.js uses Webpack to bundle and optimize the application's assets, taking advantage of Webpack's powerful module system and plugin ecosystem.
• SWC (Speedy Web Compiler): Next.js integrates the SWC compiler, a high-performance alternative to Babel, to improve the build process's speed and efficiency.
• Asynchronous Execution: Next.js utilizes asynchronous primitives, such as AsyncLocalStorage and AbortController, to manage the state and control flow of server-side operations.
• Modular Design: The codebase is organized into well-defined directories and modules, promoting code reuse, maintainability, and testability.
• Comprehensive Testing: The Next.js repository includes a vast array of tests, covering various aspects of the framework's functionality, including server-side rendering, client-side routing, and build process.

For more detailed information about the specific functionality and implementation details of the Next.js framework, please refer to the following sections of the wiki:

Server-Side Rendering Client-Side Routing Build Process

References: packages/next/src

The core functionality of the Next.js framework can be broadly categorized into three main areas: server-side rendering, client-side routing, and the build process.

References: packages/next/src/server, packages/next/src/server/app-render, packages/next/src/server/api-utils

The core functionality of the …/app-render directory is to handle the server-side rendering (SSR) and static site generation (SSG) in Next.js applications. This includes the following key features:

References: packages/next/src/client, packages/next/src/shared/lib/router

The functionality provided by Next.js for client-side routing includes the handling of navigation, prefetching, and server actions. This is primarily implemented in the …/components directory.

References: packages/next/src/build

The …/webpack directory contains the implementation of the Webpack configuration and related functionality for a Next.js application.

References: packages/create-next-app, examples

The create-next-app tool provided by Next.js is the official way to bootstrap a new Next.js application. This tool provides a seamless and customizable experience for setting up a new Next.js project, allowing developers to choose between TypeScript or JavaScript, enable Tailwind CSS and ESLint, and even start with a pre-built example project.

References: packages/create-next-app

The create-next-app tool provided by Next.js is the official way to bootstrap a new Next.js application. This tool provides a seamless and customizable experience for setting up a new Next.js project, allowing developers to choose between TypeScript or JavaScript, enable Tailwind CSS and ESLint, and even start with a pre-built example project.

References: examples

The …/cms-wordpress directory contains a Next.js-based blog application that uses WordPress as the content management system (CMS). The key functionality is divided into several components and modules:

References: scripts, packages/next-bundle-analyzer, packages/next-codemod

The Next.js repository contains a variety of configuration files, scripts, and utilities that manage various aspects of the project, such as linting, release management, and performance optimization.

References: scripts/minimal-server.js, scripts/check-pre-compiled.sh

The minimal-server.js script is responsible for optimizing the performance of the Next.js project by providing a minimal server setup for running a Next.js application in production mode. It includes several features to help developers debug and optimize the performance of their applications.

References: packages/third-parties

The Next.js framework provides a set of components and utilities for efficiently integrating various third-party services and APIs into a web application. This functionality is primarily located in the …/ directory.

References: packages/third-parties/src/google

The Next.js repository provides functionality for integrating various Google services into a Next.js application, including Google Maps, YouTube, Tag Manager, and Analytics.

References: packages/third-parties/src/ThirdPartyScriptEmbed.tsx

The ThirdPartyScriptEmbed component in the …/ThirdPartyScriptEmbed.tsx file provides functionality for securely embedding third-party scripts and HTML content within a Next.js application.

References: packages/third-parties/src/types

The …/types directory contains TypeScript type definitions for integrating various third-party services and APIs into a Next.js application. The main functionality provided by this directory includes:

References: packages/next/font

The Next.js framework provides robust functionality for handling font-related features, including the integration of Google Fonts and the optimization of locally-hosted fonts.

References: packages/next/font/google

The next/font/google directory provides functionality for integrating Google Fonts into a Next.js application. The main implementation is located in the next/dist/compiled/@next/font/dist/google module, which is re-exported through the next/font/google/index.d.ts declaration file.

References: packages/next/font/local

The …/ directory in the Next.js codebase contains functionality related to handling locally-hosted font files within Next.js applications. The key components in this directory are:

References: test/development

The Next.js framework provides robust error handling and reporting capabilities, with a focus on providing a seamless development experience. The key functionality in this area includes:

References: test/development/acceptance, test/development/acceptance-app

The React Refresh and Error Overlay functionality in Next.js is responsible for providing a seamless development experience by handling errors and updating components without a full page refresh.

References: test/development/acceptance-app

The …/rsc-runtime-errors.test.ts file contains a test suite that verifies the behavior of the Next.js error overlay when dealing with runtime errors in React Server Components (RSCs). The tests cover the following scenarios:

References: test/development/app-dir

The Next.js framework provides robust error handling and logging functionality when using the "app directory" feature. This functionality is primarily implemented in the following directories and files:

References: test/development/middleware-errors

The error handling and logging behavior of Next.js middleware in a development environment is tested extensively in the …/middleware-errors directory. This directory contains files and subdirectories that simulate different types of errors that can occur in the middleware during the loading process.

References: test/development/app-render-error-log

The error handling and logging behavior of Next.js when errors occur during page rendering is implemented in the …/app-render-error-log directory. This directory contains a test suite that verifies the logging behavior when an error occurs during the rendering of a standard page and a page using the Edge runtime.

References: test/production/app-dir-edge-runtime-with-wasm

Next.js provides functionality to support the Edge runtime and the integration of WebAssembly (WASM) in Next.js applications. This is demonstrated in the …/app-dir-edge-runtime-with-wasm directory, which contains a test suite for a Next.js application that uses WASM in the Edge runtime.

References: test/production/app-dir

The "App" Directory Structure

References: test/production/app-dir/parallel-routes-static

The functionality related to handling parallel routes in the "app" directory structure is implemented in the …/parallel-routes-static directory. This directory contains a Next.js application that demonstrates the use of parallel routes in the app directory.

References: test/production/app-dir/parallel-routes-static

The functionality provided by Next.js to generate static files for the "app" directory structure is centered around the parallel routes feature. The key aspects of this functionality are:

References: test/production/app-dir/revalidate

The revalidate.test.ts file contains a test suite that verifies the revalidation functionality of a Next.js application in the "app" directory structure. The test case performs the following steps:

References: test/production/app-dir/unexpected-error

The Next.js repository provides functionality to handle unexpected errors that occur in the "app" directory structure. This includes scenarios where errors happen during Incremental Static Regeneration (ISR) and Server-Side Rendering (SSR) processes.

References: test/production/app-dir/symbolic-file-links

The …/symbolic-file-links directory contains a test suite that verifies the functionality of the Next.js framework when dealing with symbolic file links in the "app" directory structure.

References: test/production/app-dir/client-components-tree-shaking

The Next.js repository includes functionality for client-side component tree shaking, which ensures that only the necessary components are included in the browser bundle, reducing its size and improving performance.

References: test/production/app-dir/typed-routes-with-webpack-worker

The functionality related to typed routes and webpack build worker in the "app" directory structure is as follows:

References: test/production/app-dir/app-only-flag

The "app-only" flag in the "app" directory structure of Next.js is a feature that allows developers to serve content exclusively from the "app" directory, effectively disabling the traditional "pages" directory.

References: test/production/app-dir/app-fetch-build-cache

The …/app-fetch-build-cache directory contains the core functionality of a Next.js application that fetches data during the build process and caches it.

References: test/production/app-dir/build-output

The …/build-output directory contains functionality related to verifying the build output of a Next.js application using the "app" directory structure.

References: test/production/app-dir/subresource-integrity

The Next.js framework provides functionality to handle Subresource Integrity (SRI) in the "app" directory structure. This feature helps protect the application's static assets, such as scripts and stylesheets, from tampering by ensuring their integrity.

References: test/production/app-dir/worker-restart

The Next.js framework provides functionality to handle worker restarts when generating static pages in the "app" directory structure. This is particularly important when a page takes longer than the configured timeout to generate, as the framework needs to gracefully handle these situations without failing.

References: test/production/app-dir/deopted-into-client-rendering-warning

The "Deopted into Client Rendering Warning" subsection covers the functionality related to handling the warning that is displayed when a Next.js application is "deopted" into client-side rendering, rather than being rendered server-side as expected.