SDK build tools

This directory contains templates and scripts used to build and consume SDKs in the Fuchsia GN build.

Overview

The build output of “an SDK build” is a manifest file describing the various elements of the SDK, the files that constitute them, as well as metadata.

Metadata includes the nature of an element (e.g. programming language(s), runtime type), its relationship with other elements (e.g. dependencies, supporting tools), the context in which the element was constructed (e.g. target architecture, high-level compilation options), etc...

The packaging of an SDK is a post-build step using this manifest as a blueprint.

A single build can produce multiple SDK manifests.

Implementation

Individual elements are declared using the sdk_atom template. It should be rare for a developer to directly use that template though: in most instances its use should be wrapped by another higher-level template, such as language-based templates.

Groups of atoms are declared with the sdk_molecule template. A molecule can also depend on other molecules. Molecules are a great way to provide hierarchy to SDK atoms.

Declaring SDK elements

There are a few GN templates developers should use to enable the inclusion of their code in an SDK:

sdk_shared_library
sdk_source_set
sdk_static_library
sdk_group A target //foo/bar declared with one of these templates will yield an additional target //foo/bar:bar_sdk which is an atom ready to be included in an SDK.

Additionally, the sdk template should be used to declare an SDK.

Creating a custom SDK

Identify the atoms needed in the SDK;
Create a new SDK //my/api with the sdk template, regrouping the atoms and molecules that should be included;
Add a new package file for the molecule:

{
  "labels": [
    "//my/api"
  ]
}

The package file can now be used in a standard Fuchsia build and will produce the manifest at //out/foobar/gen/my/api/api.sdk