Use cache directory to store build files

[ZerdoX-x]

$HOME/Library/Caches in macos (os x)
$XDG_CACHE_HOME/ttfautohint-build (with fallback) in linux

solves #38

[ZerdoX-x]

I am not very good at bash so please test it. Especially I am not sure about OS X recognition

[chrissimpkins]

Thank you!

Reviewing some background on your approach here and will document in the thread below.

[chrissimpkins]

From Apple docs on Library/Caches dir:

Contains cached data that can be regenerated as needed. Apps should never rely on the existence of cache files. Cache files should be placed in a directory whose name matches the bundle identifier of the app.

By convention, apps should store cache files in a subdirectory whose name matches the bundle identifier of the app. For example, if your app is named MyApp and has the bundle identifier com.example.MyApp, you would put user-specific cache files in the ~/Library/Caches/com.example.MyApp/ directory.

[chrissimpkins]

Do you know how broadly accepted / implemented the XDG spec is across Linux distros? Is this a Debian-specific issue or do applications commonly use this approach everywhere in Linux env's?

[chrissimpkins]

From SO re portability of the $OSTYPE environment variable for platform detection:

The OSTYPE environment variable is not recognized by the original Bourne shell

It looks like this may limit our shell support? Perhaps we go with a uname approach instead?

[ZerdoX-x]

From Apple docs on Library/Caches dir:

Yep, thanks for the docs. So we only store build cache files? If yes, this is the right place.

Do you know how broadly accepted / implemented the XDG spec is across Linux distros?

This thing should not be implemented by any distro. It it accepted by the most applications (and it's mostly accepted if it's specific linux only application). Here is a huge list of them: https://wiki.archlinux.org/title/XDG_Base_Directory (list is not full of course) -- here you can see programs and apps that do implement this spec, has workaround or has hardcoded path.
This xdg spec should be treated similar way as windows says to install programs to C:\Program Files and C:\Program Files(x86), (this should be the default installation path, but user can change it).

Is this a Debian-specific issue?

Not related to distro at all. I am using arch and void linux

Or do applications commonly use this approach everywhere in Linux env's?

Yep. I can provide example like alacritty
And even git changed default path from ~/.gitconfig to XDG_CONFIG_HOME/git/config. Both git and alacritty are cross platform of course

UPDATE: I did some changes to the path in a commit above, check it again please

[chrissimpkins]

Thank you!

I updated our CI tests to use GitHub Actions and rebased your changes here on the master branch updates so that we can run the tests. If everything passes, let's merge this and cut a new release with your updates.

[chrissimpkins]

Mind updating the string check syntax fail in the shellcheck lint so that it passes POSIX sh tests?

https://github.com/koalaman/shellcheck/wiki/SC2039#testing-equality

See SO answer https://stackoverflow.com/a/1089852/2848172 for details.

I think that the following syntax change in your if / else block may do the trick:

if [ "$OS" = "Darwin"* ]; then

[chrissimpkins]

#39 (comment)

[ZerdoX-x]

Need some help converting from [[ "$OS" = "Darwin"* ]] to posix friendly grep as [[ ]] not supported.

stackoverflow.com/a/59553621