b70b5429d0
This has been a nightmare in terms of the complexity to our dependency system and the whack-a-mole required on bugs. If a Requirement resolves to a Formula it should just use `depends_on "formula"` instead. This matches the effective behaviour all users of bottles (the vast majority of users and installs) and what we're doing in Homebrew/homebrew-core.
1.4 KiB
Building Against Non-Homebrew Dependencies
History
Originally Homebrew was a build-from-source package manager and all user environment variables and non-Homebrew-installed software were available to builds. Since then Homebrew added Requirements to specify dependencies on non-Homebrew software (such as those provided by brew cask like X11/XQuartz), the superenv build system to strip out unspecified dependencies, environment filtering to stop the user environment leaking into Homebrew builds and default_formula to specify that a Requirement can be satisifed by a particular formula.
As Homebrew became primarily a binary package manager, most users were fulfilling Requirements with the default_formula, not with arbitrary alternatives. To improve quality and reduce variation, Homebrew now exclusively supports using the default formula, as an ordinary dependency, and no longer supports using arbitrary alternatives.
Today
If you wish to build against custom non-Homebrew dependencies that are provided by Homebrew (e.g. a non-Homebrew, non-macOS ruby) then you must create and maintain your own tap as these formulae will not be accepted in Homebrew/homebrew-core. Once you have done that you can specify env :std in the formula which will allow a e.g. which ruby to access your existing PATH variable and allow compilation to link against this Ruby.