Add subcommand to download the crate source

[gsingh93]

It would be nice to be able to download the source for a crates.io crate. Currently, I either google the repository name to find the github page, or find the crate on crates.io and find the repository link on the crate page. Not only is this process long, but it also may not always work as some crates may have generic and hard to search names, may be hosted on less popular hosting platforms, or may not have include the repository link in the manifest.

A subcommand would be useful to quickly download the source without running into these issues.

[withoutboats]

cc me

[JanLikar]

How do you think this subcommand should be named? Should it essentially work like git clone?

[gsingh93]

Maybe cargo source or cargo get-source? I prefer the former but don't feel too strongly about the name.

[alexcrichton]

@JanLikar yeah I've thought in the past that cargo clone may be a good name for something like this, it could even check out the git repo if it's available or just download the source from crates.io (depending on what's selected)

[JanLikar]

I'm willing to do this, but I would need some guidance. @alexcrichton, would you be my mentor?

[alexcrichton]

Certainly! You'll likely want to start this outside of this repo and use the cargo crate on crates.io Once you've got that you'll do something along the lines of:

• Construct a Source. This is done through various concrete implementations which are found in src/cargo/sources
• Update the source
• Download the package
• Call get to get the Package from which you can get the source.

You may want to also explore other cargo subcommands to explore how to set up the CLI.

[JanLikar]

Why shouldn't I just work with a copy of the master branch?

[retep998]

@JanLikar Because it is fairly trivial to cargo install an external version so that as soon as you get it written and working, people can immediately use it without having to wait for it to get merged into cargo and proliferate into the version of Rust they use. Also it acts as a sort of stabilization period.

[alexcrichton]

@JanLikar yeah what @retep998 says is right, and we also unfortunately can't have "unstable cargo subcommands" so anything added would be instantly stable, and we may not be ready to commit to this.

[lifthrasiir]

FYI @JanLikar has since created the cargo-clone for this exact purpose. (I note that here because I was asked about the feature and found that the subcommand is not yet mentioned in this issue.)

[joshtriplett]

cargo-clone is useful; however, it would also be nice to have a cargo-download that downloads the .crate file, with checksum verification (and optional specification of a version other than the latest).

[lilianmoraru]

I will give you one example where this would be useful to have directly inside cargo:
In CI builds you need some Rust tool and you would like to cache the build of that, so you don't waste minutes building the tool every time.
Installing another tool here would defeat the purpose - you still sit through cargo's downloads and compilation into a temporary directory that you cannot cache.

[stale]

As there hasn't been any activity here in over 6 months I've marked this as stale and if no further activity happens for 7 days I will close it.

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[joshtriplett]

This issue still exists.

The next step would be the implementation of a command (cargo download or cargo source, not sure which name makes more sense) which would download the .crate file for a crate, and optionally unpack it into a directory.

[durka]

cargo-download may cover this.

[withoutboats]

I'm inclined to close this issue. Multiple implementations as third party tools exist, and we'd want an RFC to add a built-in command to cargo. I think there's no further progress that can be made in this repository without an RFC.

[joshtriplett]

That's fair; the next step is probably an RFC, not further implementation work.

[epage]

Another potentially similar command: https://github.com/nakabonne/rhack

[Nemo157]

Yet another third-party implementation of this: cargo-dl. The major difference of this (and why I wrote it to replace my previous cargo download usage) is that it verifies the checksums to detect IO issues like cargo-download has. (It also has a couple user-friendly features like grabbing existing tarballs from cargo's cache if they exist, parallel downloading so you can quickly grab a range of versions cargo dl -e serde@=1.0.{0..9}, and not defaulting to dumping binary gzip data to stdout).

[lolbinarycat]

just want to mention two existing commands that fetch package sources: cargo fetch and cargo vendor.

adding a flag to cargo fetch that would allow fetching an individual package and print the directory of that package would be one possible solution.