Explicitly tracked lists of generated dependencies in MODULE.bazel

[UebelAndre]

I just came across https://github.com/bazelbuild/rules_rust/blob/0.35.0/MODULE.bazel#L35-L124 and think this is a pretty egregious regression in maintainability for me. Any dependency here that's generated by a crate_universe rule needs to be updatable by the same rule or some other .bzl file rendered to contain the appropriate list.

[UebelAndre]

cc @illicitonion @matts1 is this something that will be addressed soon?

[illicitonion]

From https://github.com/bazelbuild/rules_rust/pull/2314:

Note that the MODULE.bazel changes in use_repo are autogenerated, and if you change the third party crates you depend on, you should get an error message saying something like "run this command to fix it" on your bzlmod presubmit environment.

I didn't test this out - did you run into this? What happened?

[UebelAndre]

I didn't test this out - did you run into this? What happened?

(13:20:44) WARNING: /workdir/MODULE.bazel:35:30: The module extension internal_deps defined in @rules_rust//rust/private:extensions.bzl reported incorrect imports of repositories via use_repo():

Imported, but not created by the extension (will cause the build to fail):
    rules_rust_bindgen__bindgen-0.65.1, rules_rust_bindgen__bindgen-cli-0.65.1

Not imported, but reported as direct dependencies by the extension (may cause the build to fail):
    rules_rust_bindgen__bindgen-0.69.1, rules_rust_bindgen__bindgen-cli-0.69.1

 ** You can use the following buildozer command to fix these issues:

buildozer 'use_repo_add @rules_rust//rust/private:extensions.bzl internal_deps rules_rust_bindgen__bindgen-0.69.1 rules_rust_bindgen__bindgen-cli-0.69.1' 'use_repo_remove @rules_rust//rust/private:extensions.bzl internal_deps rules_rust_bindgen__bindgen-0.65.1 rules_rust_bindgen__bindgen-cli-0.65.1' //MODULE.bazel:all

I don't have buildozer installed. I also don't think relying on buildozer is a good solution. I intended to update dependencies by running a crates_vendor target and that should have been all I needed to do. Can this list be rendered into another bzl file and loaded in MODULE.bazel instead (I genuinely have no idea what you can do with bzlmod)?

[illicitonion]

I'm pretty sure MODULE.bazel isn't allowed to load :( It's one of the pain-points the bzlmod folks are trying to work out how to improve without opening up too much power/complexity.

Personally I'm ok to rely on buildozer... I think we could probably automate fetching/running buildozer as part of running crates_vendor?

But I'll let @matts1 chime in (and also cc @meteorcloudy and @Wyverald)

[UebelAndre]

The lack of load feels like an annoying limitation but I'd be happy with buildozer. I care most that there's only one action needed to update dependencies using crate_universe. So bazel run //crate_universe/3rdparty:crates_vendor -- --repin should be all that's necessary if I wanted to update the dependencies of crate_universe itself.

[matts1]

In order to solve that issue, the only way to do it is to use the hub-and-spoke model, like I use in #1910.

That also means you don't need to update the MODULE.bazel, so you don't need to use buildozer.

Essentially, we would generate @crate_universe_anyhow//:anyhow and @crate_universe_clap, then create a repository @crate_universe for which the BUILD.bazel contains

alias(name = "anyhow", actual = "@crate_universe_anyhow//:anyhow")
alias(name = "clap", actual = "@crate_universe_anyhow//:clap")

Then instead of referring to @crate_universe_anyhow//:anyhow, you'd have to refer to @crate_universe//:anyhow. This gets around the visibility issues because the main repo doesn't need to be able to see the @crate_universe_anyhow repo.

Pretty sure that once someone implements proper vendored crates for bzlmod, we should get this for free.