Slangpy Debug

Debugging with slangpy repro steps

When debugging slangpy compatibility issues or testing Slang changes against slangpy, follow these steps to build slangpy from source using your local Slang build.

Prerequisites:

• Python 3.10+ installed
• Slang built in Debug or Release configuration
• Git with submodules support

Step 1: Build Slang

# From Slang repository root
cmake --preset default
cmake --build --preset debug    # or --preset release

Step 2: Clone slangpy Repository

# Clone with submodules (required for slangpy build)
git clone https://github.com/shader-slang/slangpy.git external/slangpy
cd external/slangpy
git submodule update --init --recursive

Read external/slangpy/CLAUDE.md for general information about the repo.

Step 3: Build and Install slangpy with Local Slang

On Windows:

cd external/slangpy
SET CMAKE_ARGS=-DSGL_LOCAL_SLANG=ON -DSGL_LOCAL_SLANG_DIR=../.. -DSGL_LOCAL_SLANG_BUILD_DIR=build/Debug
python.exe -m pip install -e .

On Linux/macOS:

cd external/slangpy
CMAKE_ARGS="-DSGL_LOCAL_SLANG=ON -DSGL_LOCAL_SLANG_DIR=../.. -DSGL_LOCAL_SLANG_BUILD_DIR=build/Debug" python -m pip install -e .

On Windows WSL:

cd external/slangpy
WSLENV+=:CMAKE_ARGS CMAKE_ARGS='-DSGL_LOCAL_SLANG=ON -DSGL_LOCAL_SLANG_DIR=../.. -DSGL_LOCAL_SLANG_BUILD_DIR=build/Debug' python.exe -m pip install -e .

Step 4: Install Test Dependencies

# From external/slangpy directory
python -m pip install -r requirements-dev.txt --user
python -m pip install pytest-xdist --user

Step 5: Run Tests

Write a test case under external/slangpy/slangpy/tests and run it with pytest.

The following example is to run all of the existing slangpy tests:

# From external/slangpy directory
python -m pytest slangpy/tests -ra -n auto --maxprocesses=3
python tools/ci.py unit-test-python

Notes

• Use -DSGL_LOCAL_SLANG_BUILD_DIR=build/Release for Release builds
• The -e flag installs in editable mode, allowing you to modify slangpy source
• Tests run in parallel with -n auto for faster execution
• Some tests may skip if GPU hardware is not available

Troubleshooting

• If tests fail to find slangc, verify the SLANG_BUILD_DIR path is correct
• If import fails, check that slangpy was installed: python -c "import slangpy; print(slangpy.__file__)"
• For GPU-specific test failures, ensure drivers are up to date

Interactive Workflow

If $ARGUMENTS specifies a build type (debug or release), use that. Otherwise default to debug.

1. Check if slangpy is already cloned at external/slangpy/
2. If not, clone it (Step 2)
3. Build and install with the appropriate build type
4. Ask the user what test to run or what issue to investigate