Sparse registry causes incorrect msrv detection [consider after release of Rust 1.70]

[ecton]

In my ~/cargo/config.toml, I've included these lines to enable the sparse registry, which is a new feature in 1.68:

[registries.crates-io]
protocol = "sparse"

When running cargo msrv on a project whose real MSRV is 1.65.0, I get this output when it's testing versions before 1.68:

 error: failed to get `criterion` as a dependency of package `benchmarks v0.1.0 (/home/ecton/projects/objectmap/benchmarks)`                                                     │
│                                                                                                                                                                                 │
│ Caused by:                                                                                                                                                                      │
│   failed to load source for dependency `criterion`                                                                                                                              │
│                                                                                                                                                                                 │
│ Caused by:                                                                                                                                                                      │
│   Unable to update registry `crates-io`                                                                                                                                         │
│                                                                                                                                                                                 │
│ Caused by:                                                                                                                                                                      │
│   usage of sparse registries requires `-Z sparse-registry`    

I have no idea if cargo-msrv can instruct cargo to not use the sparse registry. If not, maybe the tool can detect that the setting is enabled and display a warning or error.

Disabling the sparse protocol allows the correct MSRV to be detected.

I couldn't find an existing issue where this has been reported -- sorry if this is a duplicate!

Update: A friend pointed out to me that in 1.70 (~4 days from now), the sparse protocol will be enabled by default. This means that once I have 1.70 as my default toolchain, I can remove the lines in config.toml, which causes this issue to be a non-issue.

[foresterre]

Update: A friend pointed out to me that in 1.70 (~4 days from now), the sparse protocol will be enabled by default. This means that once I have 1.70 as my default toolchain, I can remove the lines in config.toml, which causes this issue to be a non-issue.

In that case I'll wait for 1.70 to be released; and will assess whether support should be added separately after the release.

Regardless, thanks for the report!

[luukvanderduim]

With cargo-msrv 0.15.1 I see "invalid" MSRV.
(Not sure if the advice is really invalid, it concerns a hiatus in a few versions)

When running in the workspace of atspi 0.18

Check for toolchain '1.67.1-x86_64-unknown-linux-gnu' failed with:
┌──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
│ error: failed to get `enumflags2` as a dependency of package `atspi-common v0.2.0 (/atspi/atspi-common)`                                                                        │
│                                                                                                                                                                                                                  │
│ Caused by:                                                                                                                                                                                                       │
│   failed to load source for dependency `enumflags2`                                                                                                                                                              │
│                                                                                                                                                                                                                  │
│ Caused by:                                                                                                                                                                                                       │
│   Unable to update registry `crates-io`                                                                                                                                                                          │
│                                                                                                                                                                                                                  │
│ Caused by:                                                                                                                                                                                                       │
│   usage of sparse registries requires `-Z sparse-registry`                                                                                                                                                       │
└──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
Check for toolchain '1.69.0-x86_64-unknown-linux-gnu' succeeded
Check for toolchain '1.68.2-x86_64-unknown-linux-gnu' succeeded
  Finished The MSRV is: 1.68.2 

When cargo +1.65.0-x86_64-unknown-linux-gnu check is run manually however, this succeeds.

    Finished dev [unoptimized + debuginfo] target(s) in 0.16s

However:
cargo +1.66.0-x86_64-unknown-linux-gnu check fails:

error: failed to get `enumflags2` as a dependency of package `atspi-common v0.2.0 (/home/luuk/code/atspi-various-doc/atspi/atspi-common)`

Caused by:
  failed to load source for dependency `enumflags2`

Caused by:
  Unable to update registry `crates-io`

Caused by:
  usage of sparse registries requires `-Z sparse-registry`

Versions prior to 1.65 are known to not compile atspi because it uses let - else constructions,

build summaries:
1.65.0 fine
1.66.0 sparse registry requires -Z sparse-registry,
1.67.1 sparse registry requires -Z sparse-registry,
1.68.2 fine
1.69.0 fine
1.70.0 fine
1.71.0 fine

Note that it does not matter if the dev-dependency of enumflags2 is inherited from the workspace or explicitly versioned in-place.

I think the advice on MSRV is sound, however the hiatus is odd and it may be valuable to others to know.

Also, it might be possible I am doing something wrong, in which case I'd be happy to learn.