Issues caused by unexpected semver version handling

[mhristache]

Hi

I have a crate which depends on both ssh2 and hyper. Hyper is using openssl-sys 0.6.7 but ssh2-rs is using libssh2-sys which moved to openssl-sys 0.7.0 recently, without changing the MINOR version. This creates issues:

$ cargo build
native library `openssl` is being linked to by more than one package, and can only be linked to by one package

  openssl-sys v0.6.7
  openssl-sys v0.7.0

The workaround is to explicitly specify libssh2-sys older version in Cargo.toml, which is strange as I am only directly using ssh2-rs so I should not care about its dependencies:

[dependencies]
ssh2 = "0.2.9"
libssh2-sys = "=0.1.31"

I think openssh2-sys should increase the minor version when any of its dependencies is bumped with a new minor version. Then ssh2-rs should also raise the minor version accordingly when moving to the new libssh2-sys.That should make it possible for the user to control everything by specifying the ssh2-rs version only. I guess this is a lot of work as rust tends to favour many small crates but I think it is the right approach. Might also be a good idea if cratos.io force this kind of behaviour.

[alexcrichton]

I've just pushed a version which is compatible with both openssl-sys versions, which should hopefully help alleviate this!

[mhristache]

Hi

Thanks, but it doesn't seem to help, it is still downloading openssl-sys 0.7.0:

$ cargo update
    Updating registry `https://github.com/rust-lang/crates.io-index`
      Adding libc v0.2.2
    Updating libssh2-sys v0.1.31 -> v0.1.34
    Updating libz-sys v0.1.9 -> v1.0.0
    Updating openssl-sys v0.6.7 -> v0.7.0
      Adding ws2_32-sys v0.2.1

I think you need to change the libssh2-sys and ssh2-rs minor versions to fix this properly (as suggested in the initial description).

[alexcrichton]

Ah yes that's an instance of rust-lang/cargo#2064, where you'll have to manually bring the version of openssl-sys back to 0.6.7 via cargo update -p openssl-sys:0.7.0 --precise 0.6.7 to get the lockfile you want.