Conditionally use Homebrew location for Spin plugins and templates

[kate-goldenring]

The current experience for installing spin is to either use the install script or build from source. Users should be able to install Spin using their favorite package manager, such as Homebrew. #641

I am working on creating a fermyon-spin Homebrew formula. Homebrew is sandboxed such that you can only install into a subdirectory of $HOMEBREW_PREFIX (/opt/homebrew on ARM macOs and /usr/local on Intel macOs ). The formula installs default plugins and templates to the $HOMEBREW_PREFIX/etc/fermyon-spin directory.

The plugin and templates systems look at $XDG_DATA_HOME or more specifically $HOME/Library/Application Support for macOS. This updates them to look for the existence of a brew installation of Spin and if exists, use the $HOMEBREW_PREFIX/etc/fermyon-spin directory for plugins and templates.

If a user has a brew installation of spin and another installation or local execution, there could be duplication of plugins and templates, with each executable using their expected directory

[lann]

I don't know much about homebrew but this doesn't seem right to me. If I install e.g. iTerm from homebrew and spin from source, will spin see HOMEBREW_PREFIX if its run from iTerm?

[kate-goldenring]

I don't know much about homebrew but this doesn't seem right to me. If I install e.g. iTerm from homebrew and spin from source, will spin see HOMEBREW_PREFIX if its run from iTerm?

@lann This installs the plugins to $HOMEBREW_PREFIX/var/spin iff both $HOMEBREW_PREFIX exists and $HOMEBREW_PREFIX/var/spin/plugins exists. If only $HOMEBREW_PREFIX exists (which would be the case in the above scenario), it continues with the normal installation path.

[lann]

Ohhh so the formula creates those dirs? I have no opinion then 😅

[kate-goldenring]

Ohhh so the formula creates those dirs? I have no opinion then 😅

Yes exactly. In the formula install step, those directories are created:

  def spin_datadir
      var/"spin"
  end
  
  def install
    system "#{Formula["rustup-init"].bin}/rustup-init", "-qy", "--no-modify-path"
    ENV.prepend_path "PATH", HOMEBREW_CACHE/"cargo_cache/bin"
    system "rustup", "target", "add", "wasm32-wasi", "wasm32-unknown-unknown"
    system "cargo", "install", *std_cargo_args

    (spin_datadir/"templates").mkpath
    (spin_datadir/"plugins").mkpath

    system "#{bin}/spin", "templates", "install", "--git", "https://github.com/fermyon/spin", "--upgrade"
    system "#{bin}/spin", "templates", "install", "--git", "https://github.com/fermyon/spin-python-sdk", "--upgrade"
    system "#{bin}/spin", "templates", "install", "--git", "https://github.com/fermyon/spin-js-sdk", "--upgrade"
    system "#{bin}/spin", "plugins", "update"
    system "#{bin}/spin", "plugins", "install", "js2wasm", "--yes"
    system "#{bin}/spin", "plugins", "install", "py2wasm", "--yes"
  end

[tpmccallum]

Issue added to developer documentation repository Re: documenting this work fermyon/developer#612