Crate in workspace doesn't rebuild against changed dependency, if said dependency was already built within the workspace

[crumblingstatue]

We have the following project:

Cargo.toml:

[workspace]
members = ["myapp", "mylib"]

mylib/Cargo.toml:

[package]
name = "mylib"
version = "0.1.0"

mylib/src/lib.rs:

pub fn gimme_string() -> &'static str {
    "Hello"
}

#[test]
fn test() {
    assert_eq!(gimme_string(), "Hello");
}

myapp/Cargo.toml:

[package]
name = "myapp"
version = "0.1.0"

[dependencies.mylib]
path = "../mylib"

myapp/src/main.rs:

extern crate mylib;

fn main() {
    println!("{}", mylib::gimme_string());
}

First, let's just run myapp:

[myapp]$ cargo run
   Compiling mylib v0.1.0 (file:///tmp/ws/mylib)
   Compiling myapp v0.1.0 (file:///tmp/ws/myapp)
     Running `/tmp/ws/target/debug/myapp`
Hello

Now we replace "Hello" with "Hey" in mylib:

pub fn gimme_string() -> &'static str {
    "Hey"
}

#[test]
fn test() {
    assert_eq!(gimme_string(), "Hey");
}

Let's test the changes:

[mylib]$ cargo test
   Compiling mylib v0.1.0 (file:///tmp/ws/mylib)
     Running /tmp/ws/target/debug/mylib-f6404eab34ef39c8

running 1 test
test test ... ok
...

Now let's run myapp again:

[myapp]$ cargo run
   Compiling myapp v0.1.0 (file:///tmp/ws/myapp)
     Running `/tmp/ws/target/debug/myapp`
Hello

Wait, what? I'm pretty sure I changed "Hello" to "Hey".

[alexcrichton]

Oh dear, sounds bad! I'll take a look