Check availabilty of all depedencies when building if necessary

[deepestsound]

Description

This PR checks that all required dependencies are available when building with --mode full or --mode docgen.
This is done before any building or compilation.

Advantages

• All dependencies fails are reported in one invocation, it doesn't stop immediately
• The error message reports the names of the packages needed to be installed
• All dependencies names are in a single structure for easy housekeeping

Disadvantages

• For now it is entirely dependent on pkg-config and its clones
• Suggested package names are not the same in all repositories (mpfr-devel on Fedora, libmpfr-dev on Ubuntu, etc.)

Todo

This only works on Linux, I have not tested or written this to work on Windows or MacOs.

Future Directions

It would be nice to make sure this system works on all major distros and that package names in the error message were applicable to most repositories, for now I just used the names correct for Red Hat/Fedora/Rocky Linux etc.
Should this problem be brute-forced by having a table like this?

const dependencies = {
   "mpfr": {
         "Fedora":  "mpfr-devel",  
         "Ubuntu": "libmpfr-dev",  
         "Arch": "mpfr"}.toTable,
   "webkit2gtk-4.1": {
         "Fedora": "webkit2gtk4.1-devel", 
         "Ubuntu": "libwebkit2gtk-4.1-dev", 
         "Arch": "webkit2gtk-4.1"}.toTable
}.toTable

and then change:

 log dependencies[fail]

to:

log dependencies[fail][hostOs]

Type of change

• Code cleanup
• Unit tests (added or updated unit-tests)
• Bug fix (non-breaking change which fixes an issue)
• Enhancement (implementation update, or general performance enhancements)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation (documentation-related additions)

[drkameleon]

OK... obviously I like your approach! Good job! 😄

I have a suggestion:

Can we somehow do it by OS/distro?
I'm not saying that you have to add the dependencies for each and every one of the systems yourself, but 💡 you could actually write/add the basic structure so that we can keep adding dependencies for new OSes.

To begin with, the dependencies table could be a table with the OSes/distros as keys and then the different dependencies as a sub-table.

As for the checking (in checkDependencies) I believe we can partly use Nim's own OS checking mechanisms (e.g. when defined(Linux) ...., etc) along with some custom distro-spotting code perhaps(?).

What I mean (obviously, the code below is off the of my head - "extremely draft-ish" warning ❗ lol):

...
var deps: Table[String,String] = {}.toTable

when defined(Linux):
      if distroIsFedora(): # I have no idea how this can be checked
                                      # but there must be a way
             deps = dependencies["Fedora"]
      else:
             discard            # for now
else:
      discard                  # for now
       
for dep in deps:
      # ...

Obviously, it can get even trickier along the way (e.g. we can't just use pkg-config on all systems - we have to even adapt our dependency checks), but I think we could make it a bit more flexible?

What do you think?

[deepestsound]

I agree with your comments.
I already have an approach to detect what distribution the script is run on and to create a table as compact as possible for all necessary combinations of packages and OSes.

[deepestsound]

I think it's in good shape, BSDs have checks bypassed for now, but the data structures already have the scaffolding needed to finish it in the future if needed.
I also wanted to know how does this PR affect this function.

[RickBarretto]

Well, looks good to me!
I've checked each review I'd made, and you managed all of them correctly.

I just added a review comment about a typo, but this is not that important, I can fix it myself.

Also, I tested locally on my machine. Obviously, I could just cover the Windows version, but ohh, well...

If CI passes and @drkameleon approves, all set up and ready 🙂!