From 719ecf3bf6ce50a8f1d02c6f96ae65e6f492321a Mon Sep 17 00:00:00 2001
From: Sam Estep <sam@samestep.com>
Date: Tue, 12 Aug 2025 11:50:15 -0400
Subject: Allow `flake.nix` users to run Vulkan tests (#8152)

This PR puts the [Khronos official Vulkan
Loader](https://github.com/NixOS/nixpkgs/blob/6027c30c8e9810896b92429f0092f624f7b1aace/pkgs/by-name/vu/vulkan-loader/package.nix#L22-L27)
in `LD_LIBRARY_PATH` for the `flake.nix` dev shell, allowing Vulkan
tests to run.

For example, before this PR:

```
$ build/Debug/bin/slang-test tests/compute/array-param.slang
Supported backends: glslang spirv-dis clang gcc genericcpp llvm spirv-opt
found test: 'tests/compute/array-param.slang'
Check vk,vulkan: Not Supported
Check cuda: Not Supported
ignored test: 'tests/compute/array-param.slang (cuda)'
passed test: 'tests/compute/array-param.slang.1 (cpu)'
ignored test: 'tests/compute/array-param.slang.2 (dx11)'
ignored test: 'tests/compute/array-param.slang.3 (dx12)'
ignored test: 'tests/compute/array-param.slang.4 (vk)'

===
100% of tests passed (1/1), 4 tests ignored
===
```

In contrast, after this PR (on an Ubuntu machine with an NVIDIA GPU):

```
$ nixGLNvidia build/Debug/bin/slang-test tests/compute/array-param.slang
Supported backends: glslang spirv-dis clang gcc genericcpp llvm spirv-opt
found test: 'tests/compute/array-param.slang'
Check vk,vulkan: Supported
Check cuda: Not Supported
ignored test: 'tests/compute/array-param.slang (cuda)'
passed test: 'tests/compute/array-param.slang.1 (cpu)'
ignored test: 'tests/compute/array-param.slang.2 (dx11)'
ignored test: 'tests/compute/array-param.slang.3 (dx12)'
passed test: 'tests/compute/array-param.slang.4 (vk)'

===
100% of tests passed (2/2), 3 tests ignored
===
```
---
 flake.nix | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/flake.nix b/flake.nix
index 3f1bf6e62..464856a4a 100644
--- a/flake.nix
+++ b/flake.nix
@@ -48,8 +48,15 @@
             pkgs.prettier
             pkgs.python3
             pkgs.shfmt
+            pkgs.vulkan-loader # Ensure this gets built to use in library path.
             pkgs.xorg.libX11
           ];
+          LD_LIBRARY_PATH = pkgs.lib.makeLibraryPath [
+            # In addition to this, running the Vulkan tests on Linux distros
+            # other than NixOS may require the use of nixGL:
+            # https://github.com/nix-community/nixGL
+            pkgs.vulkan-loader
+          ];
         };
       }
     );
-- 
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