fix: set NumPy include directory if known

src/scikit_build_core/builder/builder.py

@@ -13,6 +13,7 @@
 from ..resources import find_python
 from .generator import set_environment_for_gen
 from .sysconfig import (
+    get_numpy_include_dir,
     get_platform,
     get_python_include_dir,
     get_python_library,
@@ -148,6 +149,7 @@ def configure(
             get_python_library(self.config.env, abi3=True) if limited_abi else None
         )
         python_include_dir = get_python_include_dir()
+        numpy_include_dir = get_numpy_include_dir()
 
         # Classic Find Python
         cache_config["PYTHON_EXECUTABLE"] = sys.executable
@@ -166,6 +168,8 @@ def configure(
                 cache_config[f"{prefix}_LIBRARY"] = python_library
             if python_sabi_library and sysconfig.get_platform().startswith("win"):
                 cache_config[f"{prefix}_SABI_LIBRARY"] = python_sabi_library
+            if numpy_include_dir:
+                cache_config[f"{prefix}_NumPy_INCLUDE_DIR"] = numpy_include_dir
 
         cache_config["SKBUILD_SOABI"] = get_soabi(self.config.env, abi3=limited_abi)
 

src/scikit_build_core/builder/sysconfig.py

@@ -12,7 +12,13 @@
 if TYPE_CHECKING:
     from collections.abc import Mapping
 
-__all__ = ["get_python_include_dir", "get_python_library", "get_cmake_platform"]
+__all__ = [
+    "get_python_include_dir",
+    "get_python_library",
+    "get_cmake_platform",
+    "get_soabi",
+    "get_numpy_include_dir",
+]
 
 
 TARGET_TO_PLAT = {
@@ -154,3 +160,12 @@ def get_soabi(env: Mapping[str, str], *, abi3: bool = False) -> str:
 
     assert isinstance(ext_suffix, str)
     return ext_suffix.rsplit(".", 1)[0].lstrip(".")
+
+
+def get_numpy_include_dir() -> Path | None:
+    try:
+        import numpy as np
+    except ImportError:
+        return None
+
+    return Path(np.get_include())