add msrvcheck

[killzoner]

Which issue does this PR close?

It's an automated way to track msrv with upstream datafusion.
Currently cargo checks for msrv when adding a new dependency on latest resolver (https://rust-lang.github.io/rfcs/3537-msrv-resolver.html), not for existing ones.

Rationale for this change

This is one of the items from #1271

What changes are included in this PR?

Add a CI check to make sure MSRV is aligned with upstream datafusion projects.

Are there any user-facing changes?

No

[milenkovicm]

thanks @killzoner,
it would be great if we get a bit of documentation for this, whats expected behaviour if there is MSRV mismatch, will it fail the CI? do we check only datafusion or others as well?

[killzoner]

Hey @milenkovicm thanks for the review!

Right now we check only datafusion, as we need to make sure that there is a proper MSRV defined in the crate toml.
That's true for datafusion, but there is currently no way to check this if the dependency didn't provide any rust-version info.
This should fail the CI in case of incompatibility, I can do a commit to demonstrate it by bumping artificially ballista MSRV and see how it behaves.

Also I did a check with compat, but if we want stricter validation (like MSRV should be equal), I can change it accordingly

[killzoner]

Example of failing check with MSRV downgraded:
killzoner@6d7022f
https://github.com/killzoner/datafusion-ballista/actions/runs/18509960270/job/52748285312#step:5:636

Current project MSRV: 1.85.0
thread 'main' panicked at src/main.rs:60:17:
package 'datafusion' has MSRV 1.86.0 not compatible with current project MSRV 1.85.0

[milenkovicm]

Example of failing check with MSRV downgraded:

killzoner@6d7022f

https://github.com/killzoner/datafusion-ballista/actions/runs/18509960270/job/52748285312#step:5:636

Current project MSRV: 1.85.0

thread 'main' panicked at src/main.rs:60:17:

package 'datafusion' has MSRV 1.86.0 not compatible with current project MSRV 1.85.0

I see, should it be other way around I wonder. We need to support MSRV which datafusion supports or older

[killzoner]

Example of failing check with MSRV downgraded:
killzoner@6d7022f
https://github.com/killzoner/datafusion-ballista/actions/runs/18509960270/job/52748285312#step:5:636

Current project MSRV: 1.85.0

thread 'main' panicked at src/main.rs:60:17:

package 'datafusion' has MSRV 1.86.0 not compatible with current project MSRV 1.85.0

I see, should it be other way around I wonder. We need to support MSRV which datafusion supports or older

It's a bit counter intuitive yes, but apparently this is well this way

See usage in cargo add (https://github.com/rust-lang/cargo/blob/367fd9f213750cd40317803dd0a5a3ce3f0c676d/src/cargo/ops/cargo_add/mod.rs#L947) and other places (https://github.com/rust-lang/cargo/blob/367fd9f213750cd40317803dd0a5a3ce3f0c676d/src/cargo/ops/cargo_update.rs#L754)

Basically whenever we update a dependency (here datafusion), we should make sure to adjust the one in ballista reflecting the new potentiel MSRV from the dependencies

[milenkovicm]

all right, if I understand correctly, if datafusion is 1.85 we could decide to have ballista at 1.86 but not 1.84, as datafusion might not work in 1.84?

[killzoner]

all right, if I understand correctly, if datafusion is 1.85 we could decide to have ballista at 1.86 but not 1.84, as datafusion might not work in 1.84?

That's my understanding yes

[milenkovicm]

thanks @killzoner

[killzoner]

thanks @killzoner

Thank you for the detailed reviews