31d7bcc583
- At the AGM we formed an ad-hoc documentation working group. - One of our ideas was that we should have a last reviewed date for documentation, so that we can periodically implement a review mechanism (GitHub Actions posts to Slack for a regular documentation outdatedness check?) to track how old docs are and ensure they're still relevant. - This is a first step towards that goal, by adding a `last_review_date` to the metadata of all docs with a date of earlier than Homebrew's inception because everything needs reviewing so that we start from a good base!
16 lines
1.6 KiB
Markdown
16 lines
1.6 KiB
Markdown
---
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last_review_date: "1970-01-01"
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---
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# Building Against Non-Homebrew Dependencies
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## History
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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 `Requirement`s 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 satisfied by a particular formula.
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As Homebrew became primarily a binary package manager, most users were fulfilling `Requirement`s 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.
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## Today
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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](How-to-Create-and-Maintain-a-Tap.md) 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 e.g. `which ruby` to access your existing `PATH` variable and allow compilation to link against this Ruby. You can also [include a custom Requirement](https://github.com/Homebrew/brew/tree/HEAD/Library/Homebrew/requirements) in your formula that more accurately describes the non-Homebrew software you build against.
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