crate_universe: Generate shallow_since

[uhthomas]

I'd like to propose the crate_universe generator include shallow_since within the lock file. As it stands, transitive Cargo dependencies from git don't include shallow_since which leads to lots of log spam like:

(16:06:54) DEBUG: Rule 'crate_index__<redacted>-0.1.0' indicated that a canonical reproducible form can be obtained by modifying arguments shallow_since = "1643038190 +0000"
(16:06:54) DEBUG: Repository crate_index__<redacted>-0.1.0 instantiated at:
  /Users/thomas/code/<redacted>/WORKSPACE:198:19: in <toplevel>
  /private/var/tmp/_bazel_thomas/796dd52d4d981101108548a9446ddca6/external/crate_index/defs.bzl:1321:10: in crate_repositories
  /private/var/tmp/_bazel_thomas/796dd52d4d981101108548a9446ddca6/external/bazel_tools/tools/build_defs/repo/utils.bzl:233:18: in maybe
Repository rule new_git_repository defined at:
  /private/var/tmp/_bazel_thomas/796dd52d4d981101108548a9446ddca6/external/bazel_tools/tools/build_defs/repo/git.bzl:186:37: in <toplevel>

Consequently, the crates_repository rule then becomes filled with needless annotations for shallow_since.

[illicitonion]

+1, sounds great! Would gladly review a PR :)

[UebelAndre]

This is already an annotation you can add: https://bazelbuild.github.io/rules_rust/crate_universe.html#crate.annotation-shallow_since

Does that help?

[uhthomas]

This is already an annotation you can add: https://bazelbuild.github.io/rules_rust/crate_universe.html#crate.annotation-shallow_since

Does that help?

Sorry, what I'm suggesting avoids the need for this in most cases. We're in a situation where we have tons of annotations just for shallow_since. See:

crates_repository(
    name = "crate_index",
    annotations = {
        "crate-1": [crate.annotation(
            shallow_since = "1643039868 +0000",
        )],
        "crate-2": [crate.annotation(
            shallow_since = "1643038190 +0000",
        )],
        "crate-3": [crate.annotation(
            shallow_since = "1644511348 +0000",
        )],
        # ... and about 10 more like this
    },
    # ...
)

It would be nice for the generator to include this in the lock file automatically.

[UebelAndre]

Ah yeah, that sounds like it'd be nice. If you'd be willing to open a PR I'm sure @illicitonion or I would be happy to review it 😄

[uhthomas]

I took a quick look today and it seems like this might be a little trickier than first thought.

The Cargo.Bazel.Lock file is generated from a Cargo.lock file, which does not include this information.

Git packages would need to be fetched by the generator itself to get the correct shallow_since value.

[illicitonion]

Git packages would need to be fetched by the generator itself to get the correct shallow_since value.

I believe that cargo already fetches those repositories to .cargo/git/checkouts in order to fetch that metadata, so it should already be on disk, and just be a matter of locating it...

https://github.com/rust-lang/cargo/blob/master/src/cargo/sources/git/source.rs is the code in cargo which creates and manages git clones, which should show you how to reverse-engineer the paths.

When isolated=True we override $CARGO_HOME, and when not, we'll use default values, so that should give the base directory to be looking up from.