He-Pin opened a new issue, #3125:
URL: https://github.com/apache/pekko/issues/3125
### Motivation
`org.apache.pekko.util.Version.compareTo` contains a logic error that breaks
comparison symmetry when comparing release versions against their pre-release
counterparts (e.g. `1.2.0` vs `1.2.0-M1`).
The `rest` string comparison section uses two independent `if` statements
instead of an `if`/`else if` chain. When a release version (`rest = ""`) is
compared against a pre-release version (`rest = "M1"`), the first branch
correctly sets `diff = 1` (release > pre-release), but the second branch's
`else` clause then overwrites `diff` with `"".compareTo("M1")`, which returns a
negative value. The result incorrectly indicates that the release version is
**less than** the pre-release version.
The reverse comparison (`1.2.0-M1` vs `1.2.0`) returns the correct result,
violating the `Comparable` contract: `A.compareTo(B)` and `-B.compareTo(A)`
disagree.
### Impact
- `AbstractLeastShardAllocationStrategy` uses `appVersion.compareTo` for
shard allocation ordering. During rolling upgrades mixing release and
pre-release versions, this can cause inconsistent shard allocation decisions.
- `ManifestInfo.checkSameVersion` uses `max` on `Version` objects, which
could return the wrong version.
- Any user code relying on `Version` ordering would get incorrect results in
one comparison direction.
### Reproduction
```scala
Version("1.2.0").compareTo(Version("1.2.0-M1")) // returns negative (WRONG:
should be positive)
Version("1.2.0-M1").compareTo(Version("1.2.0")) // returns -1 (correct)
```
The existing test suite only covers `pre-release < release` but not `release
> pre-release`, which is why this asymmetry was never caught.
### Fix
The second `if` in the rest-string comparison section of `compareTo` should
be `else if` so the `else` branch (string comparison of rest values) only
executes when neither side has an empty rest string.
### References
This same bug was identified and fixed in the Akka.NET project:
https://github.com/akkadotnet/akka.net/issues/8051
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