This document briefly goes over the installer API for the updater on macOS.
The Installer API is the integration between the app installer and the updater, and is platform specific. The main functionality for doing the updates in the new updater will be an update executable (.install). The update executable will be invoked by the updater when there is an update available.
The Installer API will be called through Installer::RunApplicationInstaller(), which takes const base::FilePath& for the path to the installer and const std::string& arguments for any arguments. This will then call InstallFromDMG(), which takes the same parameters. InstallFromDMG() then executes .install with the correct arguments.
The installer DMG will have the .install executable in the root of the volume and the new application embedded within.
Currently the install executable takes just three arguments - an absolute path to the DMG, an absolute path to the currently installed app, and the version of the currently installed app. Installer::RunApplicationInstaller(), will append the existence checker path (path to the installed app) and the version from the registration into the args.
For example, Google Chrome.dmg, will contain Google Chrome.app and .install executable. Here is an example of what InstallFromDMG() will run:
i.e.
./.install "/Volumes/Google Chrome.dmg" "/Applications/Google Chrome.app" \ "81.0.416.0"
The current constraint for exit codes for the .install executable is that 0 is a successful update, and every other value is an error of some kind. For documentation on the existing exit codes for the implemented .install executable, please refer to //chrome/updater/mac/setup/.install.sh.
When executing InstallFromDMG(), there can also be cases in which the Installer API fails before the install executable is executed. These are translated from the enum updater::InstallErrors. Please refer to //chrome/updater/mac/install.h for documentation on these error codes.