3df8f70511
This adds a `UsesOnSystem` class to `OnSystem`, containing boolean instance variables to indicate which types of on_system methods are used in a formula or cask. This is intended as a replacement for `@on_system_blocks_exist`, which doesn't allow us to determine what kinds of on_system calls were used. This provides more granularity but we can still use `@uses_on_system.present?` to determine whether any on_system calls were used (and this doubles as a `nil` check in `Formula`, as the `self.class` instance variable has to use a nilable type). The `UsesOnSystem` instance variables cover the current `ARCH_OPTIONS` and `BASE_OS_OPTIONS`. At the moment, we mostly need to tell whether there are macOS/Linux or Intel/ARM on_system calls, so I've omitted instance variables for specific macOS version until we have a need for them. As a practical example, if you wanted to determine whether a cask uses Linux on_system calls, you can call `cask.uses_on_system.linux?`. The `linux` boolean will be `true` if the cask has an `on_linux` block, an `on_system` block (which requires Linux), or uses `os linux: ...`. This is something that would be challenging to determine from outside of `OnSystem` but it's relatively easy to collect the information in `OnSystem` methods and make it available like this.
Library
This directory contains all the code run by the official brew command in Homebrew and all formulae (package descriptions) in taps (repositories containing formulae) in Taps subdirectories.