Clean way to add docker-desktop cask as a dependency

[tonytrg]

Hello community 👋 ,

I would like to add docker-desktop as a dependency.
in the style of depends_on "docker", right now it would simply install that non cask dependency.

What is the best way to implement the cask as a dependency?
Other idea I have it to maybe use a post-install, which seems kinda hacky to me.

Best regards, Tony

[SMillerDev]

Is it a dependency in a cask or formula?

[tonytrg]

It exists as both, a formula and a cask.
But in my case I want the cask as dependency, and I am not sure if brew allows that.
This is the cask I am talking about. Docker-desktop-cask.
And I have a private formula, where I would like this cask as a dependency á la depends_on docker #the cask version

[SMillerDev]

So depends_on "homebrew/cask/docker-desktop should work I think.

[tonytrg]

i tried some different variations which unfortunately did not work:

• depends_on "homebrew/cask/docker-desktop"
• depends_on cask: "homebrew/cask/docker-desktop"
• depends_on cask "homebrew/cask/docker-desktop"

In the cookbook under the chaption Specifying other formulae as dependencies it states this:

A Symbol (e.g. :xcode) specifies a Requirement which can be fulfilled by one or more formulae, casks or other system-wide installed software (e.g. Xcode).

The docs seem a little bit unclear to me in this aspect. I also wonder if adding casks as dependencies should not be a more popular problem, the research I have done is conflicting. I don't see a definitive yes or no on this question.

[tonytrg]

This is the output:
brew install private-formula Running brew update --preinstall`...
==> Auto-updated Homebrew!
Updated Homebrew from be8385785 to 9c58f9a77.
No changes to formulae.

Warning: No available formula with the name "homebrew/cask/docker-desktop" (dependency of private-formula).
==> Searching for similarly named formulae...
Error: No similarly named formulae found.
==> Searching for a previously deleted formula (in the last month)...
Error: No previously deleted formula found.`

[tlk]

What is the best way to implement the cask as a dependency?

The output from grep -r -e 'depends.*cask' -e 'depends.*formula' $(brew --repository)/Library/Taps/homebrew/ seems to indicate that a cask can depend on casks and formulas, but a formula can only depend on formulas (not casks).

Here is an example of a cask that depends on the docker cask:
https://github.com/Homebrew/homebrew-cask/blob/06a31f6a264c647603193eefac0cb9e66b36df18/Casks/lando.rb#L23

[SMillerDev]

That's actually just a homebrew/core rule. As far as I know it's entirely possible to do this (because we used to in core).

[Bo98]

Depending on casks is not possible directly.

This is because Casks are still seen as "external" dependencies - they effectively just run upstream installers, so there's no real difference between a cask installation and another external installation.

What you can do is have custom requirements that inform users to install the cask first. We had a couple of them ourselves in the past when we were more lenient about Java and macFUSE: https://github.com/Homebrew/brew/blob/3.0.11/Library/Homebrew/extend/os/mac/requirements/osxfuse_requirement.rb. This will also allow people who have Docker Desktop installed outside of Homebrew/cask to still use that.

Custom requirements are embeddable inside formulae: see glibc.rb in Homebrew/core for an example, which has special requirements for bootstrapping reasons.

[tonytrg]

Thank you all for the answers.
I went with the option to add manual steps in the caveat. Since after running the formula, these are only 2-3 optional steps I did not want to create a complicated workflow.

Thank you all for the answers!