[workspace] Prereleases with path dependencies fail

[dignifiedquire]

Problem

I am not certain this is a bug, but at least it is very surprising to me:

• Using workspaces with multiple crates a and b
• b depends on a, using a = {version = "^0.1", path = "../a"}
• All is fine, e.g cargo test --all works
• Bumping a to a prerelease of 0.1.1-alpha.0 triggers the following error

$ cargo test --all
error: no matching package named `a` found
location searched: /Users/dignifiedquire/opensource/cargo-workspace-prerelease/a
perhaps you meant: a
required by package `b v0.1.0 (/Users/dignifiedquire/opensource/cargo-workspace-prerelease/b)`

Steps

1. Clone https://github.com/dignifiedquire/cargo-workspace-prerelease-bug
2. Run cargo test --all

Possible Solution(s)

It would be great if it either worked, or at least the error message was more clear as to what the actual problem is.

Notes

Output of cargo version:

cargo version
cargo 1.36.0-nightly (c4fcfb725 2019-05-15)

[ehuss]

I think this is to be expected, caret requirements do not select pre-release versions. The error message could definitely be better.

[dignifiedquire]

Is there any selector that would work? Neither *, nor ~0.1, nor >=0.1 work.

[sfackler]

0.1.1-alpha.0 will work.