regression with multiple registries error

[ehuss]

Problem

@dasbard reported that they were using an alias for a registry where two registry definitions had the same index. Starting with #10592, this is now not allowed. I don't think we anticipated users having such a configuration, so we should consider if we can avoid this regression. This results in the error:

error: multiple registries are configured with the same index url 'registry+https://…': bar, foo

Steps

Set up a configuration with two registries with the same value:

[registries.foo]
index = "https://github.com/rust-lang/crates.io-index.git"

[registries.bar]
index = "https://github.com/rust-lang/crates.io-index.git"

Possible Solution(s)

@arlosi Do you have any ideas if we can avoid an error in this situation?

Notes

No response

Version

cargo 1.68.0-nightly (70898e522 2022-12-05)
release: 1.68.0-nightly
commit-hash: 70898e522116f6c23971e2a554b2dc85fd4c84cd
commit-date: 2022-12-05
host: x86_64-apple-darwin
libgit2: 1.5.0 (sys:0.15.0 vendored)
libcurl: 7.79.1 (sys:0.4.59+curl-7.86.0 system ssl:(SecureTransport) LibreSSL/3.3.6)
os: Mac OS 12.6.0 [64-bit]

[ehuss]

We discussed this at today's team meeting, and have decided to close this as wont-fix for now. This was an intentional change as part of RFC 3139 to deal with avoiding ambiguous credentials. It may be possible to allow this situation if the configs are completely identical, but we would prefer to avoid that to keep things simple and to avoid potential confusion. We're still open to some possible workaround like that if we receive more reports of this being a problem.

I have opened #11531 to make a note of this, and will also tie into the upstream release notes when they get posted.