Cargo doesn't understand prerelease versions or build metadata

[jethrogb]

Semver allows specifying versions such as 1.0.0-beta+exp.sha.5114f85, see http://semver.org/#spec-item-9 . Cargo doesn't handle these versions well or at all. See e.g. https://crates.io/crates/core_rustc-serialize which has these versions:

• 0.3.19
• 0.3.19+patch1
• 0.3.20-v0.3.19patch1

Specifying a dependency core_rustc-serialize = "*" (or core_rustc-serialize = "^0.3") results in Cargo choosing 0.3.19, while it should choose the newer 0.3.20-v0.3.19patch1. You can't specify 0.3.20-v0.3.19patch1 in either case by using cargo update --precise. Specifying the exact version string does work.

There is simply no way to select 0.3.19+patch1. Putting it in the Cargo.toml results in the error message "the given version requirement is invalid". You also can't select it using cargo update --precise. This results in a crate existing on crates.io that can effectively not be used by anyone.

[alexcrichton]

I think this may be a dupe of #2222 which has been discussed a bit more towards the end of the thread, so I'm going to close in favor of that.

cc @steveklabnik

[jethrogb]

That bug is currently solely about prerelease versions. There's also an issue with build metadata which has not been discussed in #2222. I'm happy to move that conversation over there too, but then the issue description should be updated. Otherwise, please re-open here and I'll make this about build metadata only.

[alexcrichton]

Ah ok make sense to me, want to reopen one targeted at build metadata (may be good to start fresh). Thanks!