Products are a Fuchsia-specific feature built on top of GN to help customize Fuchsia builds. Products reference packages and coarsely define which build artifacts the packages are added to.
A product can import one or more packages into three different package sets of build artifacts, as defined below. The package sets influence what packages are included in parts of build output.
The monolith section of a product defines the list of build packages that are to be included in the disk images, system update images and package repository. Membership of a package in the monolith dependency set takes precedence over membership in other package sets.
The preinstall section of a product defines the list of build packages that are to be preinstalled in the disk image artifacts of the build, and will also be made available in the package repository. These packages are not added to the system update images or packages.
The available section of a product defines the list of build packages that are added to the package repository only. These packages will be available for runtime installation, but are not found in system update images nor are they preinstalled in any disk images. All members of monolith and preinstall are inherently available.
The default product for a layer, found in //<layer>/products/default by convention contains:
monolith - a common minimal base for this layer that makes up a system update.preinstall - a set of most commonly used development tools for the layer and other common work-items.available - all prod packages for the layer.By convention, the default product for a higher layer should be additive from the layer below.