Coverage for a single package inside a workspace

[lasantosr]

I've faced the same issue as #278, i'll try to provide a reproducible example:

Create a new workspace with the following structure:

├── Cargo.toml
├── crate-a
│   ├── Cargo.toml
│   └── src
│       └── lib.rs
└── crate-b
    ├── Cargo.toml
    └── src
        └── lib.rs

The content of the files:

• Cargo.toml:

  [workspace]
  members = ["crate-a", "crate-b"]

• crate-a/Cargo.toml:

  [package]
  name = "crate-a"
  version = "0.1.0"
  edition = "2021"
  [dependencies]

• crate-a/src/lib.rs:

  pub fn say_hello() {
      println!("Hello, world!");
  }
  
  #[cfg(test)]
  mod test {
      #[test]
      fn test_say_hello() {
          super::say_hello();
      }
  }

• crate-b/Cargo.toml:

  [package]
  name = "crate-b"
  version = "0.1.0"
  edition = "2021"
  [dependencies]
  crate-a = { path = "../crate-a" }

• crate-b/src/lib.rs:

  pub fn say_hello_goodby() {
      crate_a::say_hello();
      println!("Goodby!");
  }
  
  #[cfg(test)]
  mod test {
      #[test]
      fn test_say_hello_goodby() {
          super::say_hello_goodby();
      }
  }

Run the coverage report just for crate-b:
cargo llvm-cov --package crate-b

This is the actual output:

Filename                      Regions    Missed Regions     Cover   Functions  Missed Functions  Executed       Lines      Missed Lines     Cover    Branches   Missed Branches     Cover
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
crate-a/src/lib.rs                  1                 0   100.00%           1                 0   100.00%           3                 0   100.00%           0                 0         -
crate-b/src/lib.rs                  2                 0   100.00%           2                 0   100.00%           7                 0   100.00%           0                 0         -
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
TOTAL                               3                 0   100.00%           3                 0   100.00%          10                 0   100.00%           0                 0         -

This is the expected output:

Filename                      Regions    Missed Regions     Cover   Functions  Missed Functions  Executed       Lines      Missed Lines     Cover    Branches   Missed Branches     Cover
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
src/lib.rs                          2                 0   100.00%           2                 0   100.00%           7                 0   100.00%           0                 0         -
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
TOTAL                               2                 0   100.00%           2                 0   100.00%           7                 0   100.00%           0                 0         -

It can be achieved ignoring crate-a from the files, but it increases in complexity as the workspace has more members:
cargo llvm-cov --package crate-b --ignore-filename-regex '(^|\/)crate-a'

[taiki-e]

Thanks. The problem here appears to be similar to #303, and perhaps something in the implementation of #31 is not working well.