Request api token if necessary instead of error after building when publishing a crate

[bjorn3]

Describe the problem you are trying to solve

I forgot to login before using cargo publish. It started building the crate to verify it, but when it was finished it gave an error about not being logged in. When I logged in I had to wait for it getting built again.

Describe the solution you'd like

Either error immediately after running cargo publish without logging in first or ask for an api key.

[fluffysquirrels]

I can take a look at this.

[fluffysquirrels]

For my own benefit at least, here is the relevant control flow on the current master:

• cargo publish CLI command
• src/cargo/ops/registry.rs
  • fn publish: verifies, calls fn package to make a tarball, calls transmit
  • fn transmit: calls crates_io::Registry.publish, bails if publish is a dry-run
• src/crates-io/lib.rs: API for crates.io, (other registries too?)
  • struct Registry
  • Registry::publish does the HTTP request to "${HOST}/api/v1/crates/new", when the auth token is missing prints the error message "no upload token found, please run cargo login"

[fluffysquirrels]

So it looks like we could run the auth token check from crates-io/lib.rs' fn Registry::publish in cargo/ops/registry.rs' fn publish when the publish is not a dry-run. We already have a Registry instance at this point, so how about we keep this DRY by creating a utility method on impl Registry to check we have the necessary token?

I'm not sure what automated testing is already done on this part of the code base, I'll take a quick look at that next.

[fluffysquirrels]

grepping for the error message "no upload token found" reveals 2 call sites and 2 tests:

~/Code/cargo % rg -e "no upload token found"
src/crates-io/lib.rs
201:            None => bail!("no upload token found, please run `cargo login`"),
295:                None => bail!("no upload token found, please run `cargo login`"),

tests/testsuite/publish.rs
136:        .with_stderr_contains("[ERROR] no upload token found, please run `cargo login`")

tests/testsuite/alt_registry.rs
422:        .with_stderr_contains("error: no upload token found, please run `cargo login`")

So this error is already tested and the tests should still pass if the error message is returned earlier, so I don't anticipate changing the tests substantially.

[fluffysquirrels]

Hmmm, I wrote code for this and then realised it's not I-nominated yet, as required by the contribution guidelines. I'm asking in Discord about it but until I get a reply the changes are on my branch here: https://github.com/fluffysquirrels/cargo/tree/validate-login