Porting Term into Comonicon printing system

[camilogarciabotero]

Hi @FedeClaudi

I was unsure whether to open the discussion here or in the Comonicon.jl repo, but anyways...

Since JuliaLang/julia#44527 landed, it is certainly better to use Julia as a scripting language, then it naturally comes that command line applications (CLI) may be a thing in the coming versions. There is a lot of stuff related to CLI, but one thing that is pretty useful is the design of how the CLI will take the flags, arguments, and options. Here comes the Comonicon.jl package (kudos to @Roger-luo!) it has many features and works lovely! Here is a simple example of how a function becomes a main command:

using Comonicon

@main function mycmd(arg; option="Sam", flag::Bool=false)
    @show arg
    @show option
    @show flag
end

Will give this:

It is nice, and I was fine with it. However, a time ago I came across Typer which is

[...] a library for building CLI applications that users will love using and developers will love creating. Based on Python 3.6+ type hints.

Basically applying rich to Python to create gorgeous CLIs. here is an example of it:

import typer


def main(name: str):
    print(f"Hello {name}")


if __name__ == "__main__":
    typer.run(main)

I believe this is could be achieved using Term with that panel feature and will be awesome!

[FedeClaudi]

That's very interesting, and something Term could certainly do, Term's meant to be a counterpart to rich in Python for Julia.
I'd be very happy to see this happen I could even help with the work on it. Would either you or @Roger-luo be interested in working on this?

[Roger-luo]

I probably won't have time to work on this, also I don't think we should have Comonicon depending on the Term given how heavy it is

tested on v1.8.5

julia> @time using Comonicon
  0.097803 seconds (309.89 k allocations: 21.233 MiB)

julia> @time using Term
  0.642835 seconds (1.78 M allocations: 122.588 MiB, 10.77% gc time, 0.24% compilation time)

however, one can write an extra code generator like other code generators, or we can provide a custom printer API for the Julia code generator and implement this as a separate package.

[Roger-luo]

I like the idea though it's just we don't have much latency budget in Julia to have richer built-ins.

Since JuliaLang/julia#44527 landed, it is certainly better to use Julia as a scripting language, then it naturally comes that command line applications (CLI) may be a thing in the coming versions.

I think the next step is to wait for loading time optimizations, e.g lazy sub-packages, and static compilation before that happens writing CLI applications in Julia has to be very careful to avoid unnecessary latencies.

[FedeClaudi]

That's fair.

Just a note, not sure what version of Term.jl you've used for the test above, but I've been working on improving pre-compilation so I'm hoping to bring down latency for Term.

[camilogarciabotero]

Adding some benches on v.1.9.0-beta2 and Term v.1.10

julia> @time using Term
  1.517197 seconds (1.72 M allocations: 107.844 MiB, 4.51% gc time)

Second:

julia> @time using Term
  0.000519 seconds (184 allocations: 14.078 KiB)

I know that the second execution is not actually what happens when a CLI is used, but it is now quite cheap, isn't it? Could Term v.2.0 be like the second benchmark? I switched to the master branch of Term, and tried in a fresh Julia session, and now it looks like the loading latency is quite good:

julia> @time using Term
  0.000351 seconds (184 allocations: 14.078 KiB)

[camilogarciabotero]

I'd be very happy to see this happen I could even help with the work on it.

Great, I was playing around with src/ast/print.jl API of Comonicon (which I thought could be a nice starting point) and have some troubles with Term.Panel (as I'm unfamiliar with Comonicon to use them well), yet I ended up using hLine and got some differences in the CLI:

This was achieved by adding hline to what is defined as section in the printing system.

I don't think we should have Comonicon depending on the Term given how heavy it is

Regarding the dependency issue of having Term, and adding to some of what you later suggested, what if we only use part of it, like using Term: Panel or using Term:hLine? Is this helpful in reducing startup latency? I haven't noticed heavy differences while making the aforementioned changes in my local machine.

The other ideas you mentioned sound great, yet I'm not that skillful to write a code generator.

however, one can write an extra code generator like other code generators, or we can provide a custom printer API for the Julia code generator and implement this as a separate package