Implementing a livecheck mechanism to find out outdated formulas.

[youtux]

I was reading #12564 and I thought that it would be nice to have a feature to check if a formula is outdated w.r.t. the upstream, just like macports does with port livecheck.

I thought about having this kind of syntax:
brew livecheck <formula> to find out what is the latest version of the formula in the upstream;
brew livecheck outdated to list all the outdated formulas (yes, it could be a very long process);
brew livecheck installed to list all the outdated formulas that are installed;
brew livecheck to list all the outdated formulas maintained by the user (maybe they could be into an ENV variable, like HOMEBREW_WATCH).
I'd really like to help to implement such thing, but I'm trying to understand the internals of homebrew without much success. Furthermore, I don't have a good ruby-style programming experience.
Of course the syntax of a formula must be updated, but since a good number of the formulas are "github-based", we could just rely on the list of tags from git.

Let me know if I missed some sources where I can find how to contribute.

[MikeMcQuaid]

You shouldn't actually need to use much of the internals of Homebrew here. Do you have any more specific questions on something you've struggled with? I suggest just trying to implement brew livecheck as an external command for a single formula first.

[youtux]

Well, the problem is that the command would work only with the specific formula you're considering. I would like to make it available for all the formulas, but then it would be necessary to have some additional fields in the formula syntax, like

check_updated do
  # code that returns the list of available version from the upstream
end

and then the command brew livecheck <formula> would actually run that method and find if there is a version newer than the formula's one.

[MikeMcQuaid]

We won't be adding code to formulae until we have a tool that handles most of them without it, I'm afraid.

[youtux]

If I (unlikely) come up with a solution that needs just one method more (like check_updated) to be added to the formula syntax, is it possible that you accept it?

EDIT: Of course it is not mandatory, but those formulas that implement it are enabled to this function.

[MikeMcQuaid]

@youtux I don't think this needs something added to the formula syntax so currently: probably not, sorry.

[jacknagel]

I agree, adding something to the formula syntax is one of the last steps in developing a feature. It should be straightforward to implement this without touching internals. If the feature proves useful, then we can discuss adding it to core.

[youtux]

Ok, I made a basic external command at https://github.com/youtux/homebrew-livecheck.
It is very basic, but it already can check for updates for those formulae that uses git (for example, sqlmap). For the others, it is possible to extend the formula by implementing a method get_latest_version and then just merge it into my repository.

Let me know if you think it's a good idea and any other suggestion are well appreciated.

[MikeMcQuaid]

Yeh, this looks like a good approach. I'll close this out for now but might be interesting to make a note/blog/wiki for this noting which formulae you've testing it with and where it works/doesn't currently.

[youtux]

FYI the command I wrote now can display the version of all the installed formulae.
Of course most of the time it fails since not all formulae use git and there are only a few formulae that implement the livecheck functionality in my project.
Is there any way it can go on the homebrew's wiki to get some attention?

[MikeMcQuaid]

@youtux If you tweet asking for help building it and mention @MacHomebrew I'll RT you. Probably worth posting to the mailing list (homebrew@librelist.com) too.