scripts/cxx-api

Python build pipeline for React Native's C++ (and Objective-C) API snapshots.

Overview

scripts/cxx-api generates human-readable snapshots of React Native's public C++ API surface. It uses Doxygen to parse C/C++/Objective-C headers and a custom Python parser to produce a simplified, sorted representation of every public symbol.

The pipeline produces one .api snapshot file per configured API view × variant combination:

Snapshot	Description
`ReactCommonDebugCxx.api`	Platform-independent C++ API (debug)
`ReactCommonReleaseCxx.api`	Platform-independent C++ API (release)
`ReactAndroidDebugCxx.api`	Android-specific C++ API (debug)
`ReactAndroidReleaseCxx.api`	Android-specific C++ API (release)
`ReactAppleDebugCxx.api`	Apple-specific C++/Obj-C API (debug)
`ReactAppleReleaseCxx.api`	Apple-specific C++/Obj-C API (release)

For each view, debug and release variants are generated with different preprocessor definitions (e.g. REACT_NATIVE_DEBUG vs NDEBUG), since #ifdef guards in the source headers can produce a different public API surface per variant.

Snapshot files are committed to the repo under scripts/cxx-api/api-snapshots/.

Usage

Generate snapshots

Maintainers should run this command whenever making intentional C++ API changes:

python -m scripts.cxx-api.parser

Validate snapshots against committed baseline

This mode generates snapshots to a temporary directory and compares them against the committed .api files. It is designed for CI:

python -m scripts.cxx-api.parser --validate

If any snapshot differs, a unified diff is printed and the process exits with a non-zero status. To fix a failing validation, regenerate the snapshots with python -m scripts.cxx-api.parser and commit the updated .api files.

How it works

The pipeline has two main stages:

1. Doxygen XML generation

Doxygen is configured via a generated config file (built from .doxygen.config.template) with the input directories, exclude patterns, and preprocessor definitions specified in config.yml. It outputs XML describing every symbol found in the headers.

2. Snapshot parsing

The Python parser (parser/) reads the Doxygen XML output and builds a scope tree of the public API surface. The tree is then serialized to a deterministically sorted, human-readable .api text format.

When to use it

The snapshot should be regenerated whenever making intentional changes to the public C++ API surface. This includes additions, removals, and changes to files located in:

xplat/js/react-native-github/
xplat/js/react-native-github/ReactCommon/
xplat/js/react-native-github/ReactAndroid/
xplat/js/react-native-github/ReactApple/
xplat/js/react-native-github/Libraries/

Configuration

All API views and their variants are defined in config.yml. Each view specifies:

Field	Description
`inputs`	Directories to scan for headers
`exclude_patterns`	Glob patterns for files to skip
`definitions`	Preprocessor macros to define
`variants`	Named build variants (e.g. debug/release) with extra definitions
`codegen`	Optional codegen platform (`android`, `ios`) to generate TurboModule/Component headers before scanning
`private_directories`	Directories whose headers are scanned (they may be transitively included) but should not contribute public symbols. If any public API entity is defined in a private directory, a warning is printed to help catch accidental API exposure.

Snapshot format

The .api files use a minimal pseudo-C++ syntax designed for easy diffing:

namespace facebook::react {
  class ComponentDescriptor {
    public ComponentDescriptor(ComponentDescriptorParameters params);
    public ComponentHandle getComponentHandle();
  }

  enum class AccessibilityRole {
    None = 0,
    Button = 1,
  }
}

Scopes and members are sorted alphabetically.
Access specifiers (public, protected) are preserved.
Template parameters are included.
Doc comments and source file names are stripped.