react-native/__docs__/DOCS.md

React Native Technical Documentation

The React Native technical documentation describes how React Native works internally, the subsystems it is composed of, how they work and how they interact with each other.

The intended audience is people who want to learn about the internals of React Native and contribute to it. End users of React Native are meant to use the public website instead (its code can be found here).

Motivation

The goals of this documentation are:

1. To make it easier for people to understand and contribute to the React Native architecture.
2. To ensure the architecture is easy to maintain, with clearly scoped subsystems that are easy to reason about and change.

Strategy

Our documentation supports the following use cases:

1. [Exploration based] I want to understand how React Native works and learn about its different parts. I want to explore.
2. [Goal based] I want to solve a problem and change something specific, so I want to understand what I should change and how the system I need to change works. I need to understand how other systems depend on this.

To support the first case, we provide a single entrypoint for the whole documentation, which will be the first step in a tree of docs with links to parents and children:

• <root>/__docs__/README.md (with links to subsystems 1, 2, etc.)
  • Subsystem 1/__docs__/README.md (with links to root and subsystems 1.1, 1.2, etc.)
    • Subsystem 1.1/__docs__/README.md (with links to subsystem 1 and subsystems 1.1.1, 1.1.2, etc.)
    • Subsystem 1.2/__docs__/README.md
  • Subsystem 2/__docs__/README.md

This structure will make it possible for the user to navigate across the documentation organically, just following links within the documents themselves.

To support the second use case, focusing on a specific subsystem, we will describe what are the relationships between that subsystem and others, to make sure that changes to its API are understood, and that usages of other subsystems are considered.

The use of the __docs__ directory (inspired by Python) has 2 goals:

1. Make the documentation easy to find in the directory, by generally appearing at the top of the directory (similar to __tests__).
2. Grouping the documentation itself and its assets (images, diagrams, etc.).

Guidelines

Content

Use this template to write the documentation for a subsystem, adding the appropriate subsections depending on what that documentation requires. Only diverge from this structure if it is strictly necessary (removing unnecessary or empty sections is fine).

Include supporting images and diagrams in the documentation. Those assets should be placed in the same __docs__ directory as the README.md file. Use relative paths to link to the assets in those directories.

If you include Excalidraw diagrams, make sure to export an SVG image from the website using the "Embedded scene" option, so the original diagram is included in the file and can be re-uploaded to Excalidraw for future modifications. Use the extension .excalidraw.svg to signal this.

Granularity

The level of granularity in the definition of the subsystems should be enough to correctly describe how React Native works, but not so detailed that any changes in the code require changes in the documentation.

Examples:

• Requires updating the docs:
  • Adding a new major feature or API.
  • Adding a new relevant dependency. Adding a dependency to helper functions does not count as relevant.
• Does NOT require updating the docs:
  • Internal implementation details that do not change how the system works or interacts with others.
  • Making a minor API or feature change.
  • Internal refactors, even if they create new modules or introduce dependencies to external helpers.

Location

When a specific subsystem exists in multiple directories (e.g.: platform-specific ones, C++, JavaScript, etc.):

1. Choose one of them to place the canonical documentation (in order of preference, JavaScript -> C++ -> platform).
2. Create specific files in the rest linking to the canonical one.