On Windows, Git dependency with symlink source file fails to build

[azriel91]

Problem

Given a library crate contains a symlink as a source file, i.e. something.rs -> ../other/something.rs, when another crate depends on the library via a { git = ".." } dependency, then on Windows, the cloned dependency fails to build.

An example error message:

error[E0583]: file not found for module `log_disabled`
   --> D:\apps\gitlab_runner\.cargo\git\checkouts\rust-derive-builder-ac2766f218331415\67c9c95\derive_builder\src\lib.rs:576:5
    |
576 | mod log_disabled;
    |     ^^^^^^^^^^^^
    |
    = help: name the file either log_disabled.rs or log_disabled\mod.rs inside the directory "D:\apps\gitlab_runner\.cargo\git\checkouts\rust-derive-builder-ac2766f218331415\67c9c95\derive_builder\src"

Steps

1. (On Windows!), create a crate with the following dependency:

   [dependencies]
   derive_builder = { git = "https://github.com/colin-kiegel/rust-derive-builder.git" }

   # commands:
   cargo init --lib builder_test
   cd builder_test
   cat >> Cargo.toml << EOF
   derive_builder = { git = "https://github.com/colin-kiegel/rust-derive-builder.git" }
   EOF

2. cargo build

Possible Solution(s)

Not sure, but whatever cargo publish does, the consuming crate is able to build -- on the same commit, derive_builder = "0.8.0" builds successfully.

Notes

Output of cargo version: cargo 1.37.0-nightly (4c1fa54d1 2019-06-24)
OS: Windows 10 x64
Git: git version 2.23.0.windows.1
git config core.symlinks: true

cc: colin-kiegel/rust-derive-builder#149

[ehuss]

That's really strange! It looks like the issue is that libgit2 is creating symlinks with forward slashes, and those cannot be read. I have opened an upstream issue at libgit2/libgit2#5252.