Update slang-rhi deps for gfx-unit-test

[gtong-nv]

This PR marks the slang-rhi a required dependecy for platform and gfx-unit-test, and only build them when SLANG_ENABLE_SLANG_RHI=ON.
This should allow the slang still to be built without those tests components when SLANG_ENABLE_SLANG_RHI=OFF.

[samestep]

/format

[slangbot]

🌈 Formatted, please merge the changes from this PR

[samestep]

Thanks for addressing this! Unfortunately it doesn't seem to have fixed the build issue that @niklaskorz mentioned in #7577 (comment); I still get this error:

In file included from /build/source/tools/test-server/../render-test/slang-support.h:5,
                 from /build/source/tools/test-server/test-server-main.cpp:13:
/build/source/tools/test-server/../render-test/options.h:15:10: fatal error: slang-rhi.h: No such file or directory
   15 | #include <slang-rhi.h>
      |          ^~~~~~~~~~~~~

[gtong-nv]

Thanks for addressing this! Unfortunately it doesn't seem to have fixed the build issue that @niklaskorz mentioned in #7577 (comment); I still get this error:

In file included from /build/source/tools/test-server/../render-test/slang-support.h:5,
                 from /build/source/tools/test-server/test-server-main.cpp:13:
/build/source/tools/test-server/../render-test/options.h:15:10: fatal error: slang-rhi.h: No such file or directory
   15 | #include <slang-rhi.h>
      |          ^~~~~~~~~~~~~

yea, it's trickier than I thought. test-server also depends on slang-rhi, and slang-test depends on test-server. I'm checking if we can exclude slang-test if slang-rhi is OFF

[samestep]

@gtong-nv that makes sense. If it'd make it easier, I'd imagine we can also change the Nixpkgs build to use -DSLANG_ENABLE_TESTS=OFF (which I assume is how the Emscripten build in this repo gets away with using -DSLANG_ENABLE_SLANG_RHI=OFF currently); but when I tried that just now, I got a bunch of errors like this:

CMake Error at tools/CMakeLists.txt:224 (add_custom_target):
  Error evaluating generator expression:

    $<TARGET_FILE_DIR:slang-test>

  No target "slang-test"

[samestep]

Alternatively: the whole reason the Nixpkgs build disables slang-rhi in the first place is because there doesn't seem to be a way to build it without network access; would it be possible to just provide a way to build slang-rhi with a provided version of Dawn instead? Then we wouldn't need to disable slang-rhi when building Slang.

[gtong-nv]

I think we should just exclude all tests and examples from the build is SLANG-RHI is OFF, as from what I can tell, almost all of them has #include <slang-rhi.h> directly or indirectly in the source code.

[gtong-nv]

/format

[slangbot]

🌈 Formatted, please merge the changes from this PR

[samestep]

@gtong-nv thanks for fixing those earlier errors! It looks like the build still doesn't quite work with -DSLANG_ENABLE_SLANG_RHI=OFF and -DSLANG_ENABLE_TESTS=OFF though:

CMake Error at tools/cmake_install.cmake:272 (file):
  file INSTALL cannot find
  "/build/source/build/RelWithDebInfo/bin/gfx.slang": No such file or
  directory.
Call Stack (most recent call first):
  cmake_install.cmake:77 (include)

[gtong-nv]

Hi @samestep, I tried a clean build and it should work.
Tried a few presets and even just with.
mkdir build; cd build; cmake .. -DSLANG_ENABLE_SLANG_RHI=OFF -DSLANG_ENABLE_TESTS=OFF

Can you clear camke cache and try a clean build? gfx.slang should still be generated and copied to bin/ with the -DSLANG_ENABLE_GFX=ON, which should be ON by default

[samestep]

Unfortunately I have already been using a clean build :( Specifically, I've been testing this with the build setup in Nixpkgs, since that was the original motivation for this change: https://github.com/NixOS/nixpkgs/blob/596312aae91421d6923f18cecce934a7d3bfd6b8/pkgs/by-name/sh/shader-slang/package.nix

That is, one can reproduce the exact same build error by cloning Nixpkgs at that same commit:

gh repo clone NixOS/nixpkgs
git checkout 596312aae91421d6923f18cecce934a7d3bfd6b8

Then applying this patch to build with the latest commit from this branch:

diff --git a/pkgs/by-name/sh/shader-slang/package.nix b/pkgs/by-name/sh/shader-slang/package.nix
index 78edfe7f43ac..3d40aee57050 100644
--- a/pkgs/by-name/sh/shader-slang/package.nix
+++ b/pkgs/by-name/sh/shader-slang/package.nix
@@ -27,13 +27,13 @@
 
 stdenv.mkDerivation (finalAttrs: {
   pname = "shader-slang";
-  version = "2025.12.1";
+  version = "2025.14.3";
 
   src = fetchFromGitHub {
     owner = "shader-slang";
     repo = "slang";
-    tag = "v${finalAttrs.version}";
-    hash = "sha256-5M/sKoCFVGW4VcOPzL8dVhTuo+esjINPXw76fnO7OEw=";
+    rev = "c46125d22e6ecf66a8bb9b0c4b5bcaed8ee6990a";
+    hash = "sha256-8hC39nO7HbVPzSOIqHFSaq22mmwMwvd8W+zJ/ZEAh9w=";
     fetchSubmodules = true;
   };
 
@@ -118,6 +118,7 @@ stdenv.mkDerivation (finalAttrs: {
     # https://github.com/shader-slang/slang-rhi is "under active refactoring
     # and development, and is not yet ready for general use."
     "-DSLANG_ENABLE_SLANG_RHI=OFF"
+    "-DSLANG_ENABLE_TESTS=OFF"
     "-DSLANG_USE_SYSTEM_MINIZ=ON"
     "-DSLANG_USE_SYSTEM_LZ4=ON"
     "-DSLANG_SLANG_LLVM_FLAVOR=${if withLLVM then "USE_SYSTEM_LLVM" else "DISABLE"}"

Then running this command:

nix-build -A shader-slang

I also tried explicitly adding -DSLANG_ENABLE_GFX=ON and still got the same error.

@gtong-nv looking at e.g. the cmakeFlags in that pkgs/by-name/sh/shader-slang/package.nix file I linked above, do you see anything wrong that I should be changing to make this build work?

Or @niklaskorz do you happen to know how/if this build error should be fixed on the Nixpkgs side?

[niklaskorz]

Or @niklaskorz do you happen to know how/if this build error should be fixed on the Nixpkgs side?

As you already noted in #8102, this is caused by an unintended dependency of the gfx module on the tests. Adding "-DSLANG_ENABLE_GFX=OFF" to the cmakeFlags (together with "-DSLANG_ENABLE_TESTS=OFF") makes this PR pass in nix.

[samestep]

As you already noted in #8102, this is caused by an unintended dependency of the gfx module on the tests. Adding "-DSLANG_ENABLE_GFX=OFF" to the cmakeFlags (together with "-DSLANG_ENABLE_TESTS=OFF") makes this PR pass in nix.

Ah you're so right, thanks; just tried that and it does indeed work.

[gtong-nv]

Techincally, SLANG_ENABLE_GFX should be OK to turn on as nothing in the slang repo should be relying on it. The gfx.dll is still being built only because some customers are still using it.
I will investigate this and make a follow up change if needed. I think this PR can be merged first.