ARCHITECTURE.md

Architecture

This document describes the high-level architecture of Re.Pack. If you want to familiarize yourself with the code base, you are just in the right place!

Before you start, make sure you've gone through the README.

Feel free to jump between this document and Documentation for an additional context on configuration, parameters and types.

General overview

There are 2 ways to look at the content of the Re.Pack:

• by command that are exposed to React Native Community CLI
• by Webpack plugins and utilities

Here's a chart that represents both aspect of the codebase:

Structure

The following list describes the components that create Re.Pack:

• packages
  • repack — Main source code for Re.Pack
    • ios — source code for iOS native module
    • android — source coce for Android native module
    • src/
      • client/
        • runtime/ — Source code for runtime code embedded into a final bundle.
        • chunks-api/ — Source code for ChunkManager used for dealing with Code Splitting.
      • commands/ — Source code for React Native Community CLI commands.
      • server/ — Source code for Development server, proxy and all related functionality.
      • webpack/ — Source code for Webpack plugins and utilities.
  • debugger-ui — Source code for Chrome Remote JS debugger.
  • TesterApp — Example tester application.
• templates/ — Templates for files to initialize a new project.

Bundling

The core of bundling functionality is to load platform-specific Webpack configuration file, then using Webpack API, create and run a compiler.

Depending on how code is run, the final Webpack configuration might be different:

• if Webpack and Re.Pack are run by React Native Community CLI, it provides data to functions like getMode, getContext etc.
• if Webpack and Re.Pack are run by Webpack CLI, the results for functions like getMode, getContext, etc is based on fallback values.

Development server

When running a development server, there is a wide difference in the functionality provided by (webpack-)start command and Webpack CLI:

• Webpack CLI:
  • Will create platform-specific Webpack configuration, so when the compiler calls DevSeverPlugin, a platform-specific DevServer will be created.
  • The platform-specific DevServer has all the required features (debugging, symbolication, logging, message/events WebSocket server, HMR, Dev endpoints).
• webpack-start:
  • Uses DevServerProxy, which sole purpose is to allow running multiple Webpack compilers for multiple platforms.
  • Each platform will get its own compiler worker, which runs Webpack compiler in watch mode. For each compilation a platform-specific Webpack configuration will be created, which will include platform-specific DevServer.
  • Each platform-specific DevServer will listen on randomly picked free-port.
  • DevServerProxy will handle the creation of said workers, as well as forwarding the requests based on ?platform=<platform> query param.
  • Additionally DevServerProxy has the same Dev endpoints as DevServer (they both extend BaseDevServer) and dedicated POST /symbolicate endpoint.

The overall architecture of DevServerProxy is as follows:

`DevServerProxy`
├── <compiler worker platform=ios>
│   └── <webpack compilation>
│       └── `DevServerPlugin`
│           └── `DevServer`
├── <compiler worker platform=android>
│   └── <webpack compilation>
│       └── `DevServerPlugin`
│           └── `DevServer`
└── ...

Check getDevServerOptions function for details on configuration options that the DevServer or DevServerProxy will receive.

Logging

Depending on how you run Re.Pack the logging works slightly differently, but the end destination for all logs is Reporter instance — this is the place where all logs are written to the terminal and/or file. The route that each log takes to get to the reporter instance will differ.

The top-level Reporter instance will also try to broadcast logs to the connected Flipper instance under React Native -> Logs with tag repack_<type> where type can be debug, info, warn or error. Because of the Flipper tight integration with Metro all Re.Pack logs will be reported as verbose so make sure you sent the filter to include type Verbose and use searching to filter logs e.g. by typing repack_debug.

Bundling with webpack-bundle command and Webpack CLI / Running with development server via Webpack CLI

Read as stack trace, from bottom to the top.

<terminal/file>
└── Reporter
    └── LoggerPlugin
        ├── <webpack stats>
        ├── compilation.hooks.log
        └── compiler.hooks.infrastructureLog
            └── DevServerPlugin
                └── DevServer

Running with development server via webpack-start command

Read as stack trace, from bottom to the top.

<terminal>
└── Reporter
    └── DevServerProxy
        └── <compiler worker>
            └── Reporter <file: if enabled> (format: json)
                └── LoggerPlugin
                    ├── <webpack stats>
                    ├── compilation.hooks.log
                    └── compiler.hooks.infrastructureLog
                        └── DevServerPlugin
                            └── DevServer