Similar to GYP, GN is a build system designed for building Chromium. The

official builds of Node.js are built with GYP, but GN build files are also

provided as an unofficial alternative build system.

The GN build files only support a subset of the Node.js build configurations.

It's not required for all pull requests to Node.js to support GN builds, and the

CI of Node.js does not currently test GN builds, though Node.js welcomes pull

requests that improve GN support or fix breakages introduced by other pull

requests.

Currently the GN build is used by:

1. Electron for building Node.js together with Chromium.

2. V8 for testing the integration of Node.js in CI.

Node.js contains following GN build files:

* `node.gni` - Public GN arguments for configuring the build.

* `*/BUILD.gn` - This is the file where GN looks for build rules, in Node.js it

just includes the `unofficial.gni` file to avoid accidental modifications.

* `*/unofficial.gni` - The actual build rules for each component.

Unlike GYP, the GN tool does not include any built-in rules for compiling a

project, which means projects building with GN must provide their own build

configurations for things like how to invoke a C++ compiler. Chromium related

projects like V8 and skia choose to reuse Chromium's build configurations, and

V8's Node.js integration testing repository

([node-ci](https://chromium.googlesource.com/v8/node-ci/)) can be reused for

building Node.js.

The `depot_tools` is a set of tools used by Chromium related projects for

checking out code and managing dependencies, and since this guide is reusing the

infra of V8, it needs to be installed and added to `PATH`:

git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git

export PATH=/path/to/depot_tools:$PATH

You can also follow the [official tutorial of

`depot_tools`](https://commondatastorage.googleapis.com/chrome-infra-docs/flat/depot_tools/docs/html/depot_tools_tutorial.html).

To check out the latest main branch of Node.js for building, use the `fetch`

tool from `depot_tools`:

mkdir node_gn

cd node_gn

fetch node

You can choose to save some time by omitting git history:

fetch --no-history node

After syncing is done, you will get a directory structure like this:

The `node_gn` is a workspace directory, which only contains configurations and

caches of the `gclient` tool from `depot_tools`, and the repository is checked

out at `node_gn/node`.

The `node_gn/node` directory is not a checkout of Node.js, it is actually

[node-ci](https://chromium.googlesource.com/v8/node-ci/), the repository used by

V8 for testing integration with Node.js. The source code of Node.js is checked

out at `node_gn/node/node`.

GN only supports [`ninja`](https://ninja-build.org) for building, so to build

Node.js with GN, `ninja` build files should be generated first, and then

`ninja` can be invoked to do the building.

The `node-ci` repository provides a script for calling GN:

cd node # Enter `node_gn/node` which contains a node-ci checkout

./tools/gn-gen.py out/Release

which writes `ninja` build files into the `out/Release` directory under

`node_gn/node`.

And then you can execute `ninja`:

ninja -C out/Release node

After the build is completed, the compiled Node.js executable can be found in

`out/Release/node`.

Currently the GN build of Node.js is not fully functioning. It builds for macOS

and Linux, while the Windows build is still a work in progress. And some tests

are still failing with the GN build.

There are also efforts on making GN build work without using `depot_tools`,

which is tracked in the issue

[#51689](https://github.com/nodejs/node/issues/51689).