add a progress bar when fetching packages

[andrewrk]

Zig is silent while it downloads third party packages from the Internet, which could take an arbitrarily long time.

Instead, it should report the progress, network speed, and which packages it is currently on, as expected by our esteemed users.

zig/src/main.zig

Lines 4449 to 4462 in 8a18abf

	const fetch_result = build_pkg.fetchAndAddDependencies(
	&main_pkg,
	arena,
	&thread_pool,
	&http_client,
	build_directory,
	global_cache_directory,
	local_cache_directory,
	&dependencies_source,
	&build_roots_source,
	"",
	&wip_errors,
	&all_modules,
	);

[VeroAsghar]

I’m willing to attempt solving this issue! I will also respond quickly if I feel this is too far out of my wheelhouse, so that I’m not wasting anyone’s time. (I’m quite new at contributing to OSS, so I’m not sure about the normal way to show interest in a specific issue.)

[mlugg]

@VeroAsghar

I'd quite like to get a basic impl of this in for 0.11 - it'll save a lot of confusion over the next few months - so would it be possible for you to try and get it done in the next week or do? I'm happy to take it on if not, I just don't like nabbing contributor-friendly issues from people.

If you want to get started with this, you can take a look at the std.Progress API. It's not the prettiest, and maybe won't satisfy all the goals here, but is fairly easy to use and definitely works for a basic impl. You're welcome to ping me here or on Discord (@mlugg) if you've got any questions :)

[VeroAsghar]

@mlugg

Thanks for the tips!
On Discord i'm (at)jva, so that you don't have to worry about a random ping.
I'll see how far I get by Monday and can tell you then if I'm able to complete it within the coming week.
Would that be okay still? Or would you like to know earlier?

[mlugg]

@VeroAsghar that's totally fine, I'm not trying to rush you, just wanna get it in before 0.11 :) good luck!

[truemedian]

A warning about this implementation: if you want to find the length of a http response you'll need to pull it from request.response.content_length, but this field will be null for chunked messages, so you'll also need a way to handle not knowing how long the response may be.

[VeroAsghar]

So far I'm able to increment the progress bar by the amount of packages in the .zon file, with a placeholder file size.

downloading packages... [1/5] libz [1/100]

The problem I currently have is getting the content-length from the request, as fetchAndAddDependencies (where the dependency names are held) calls fetchAndUnpack (where the request is actually made). The request data does not bubble back up to fetchAndAddDependencies from fetchAndUnpack.
I'm currently trying to find a method around this.

[andrewrk]

so you'll also need a way to handle not knowing how long the response may be.

Hmmmmmmmm I think we may have stumbled our way into a proposal: #16528