CMakeConfigDeps

Author: Behemyth

cppython/build/backend.py

@@ -162,9 +162,9 @@ def _prepare_and_get_result(
 
     if result.sync_data is not None:
         if isinstance(result.sync_data, CMakeSyncData):
-            settings = _inject_cmake_toolchain(config_settings, result.sync_data.toolchain_file)
+            settings = _inject_cmake_toolchain(settings, result.sync_data.toolchain_file)
         elif isinstance(result.sync_data, MesonSyncData):
-            settings = _inject_meson_files(config_settings, result.sync_data.native_file, result.sync_data.cross_file)
+            settings = _inject_meson_files(settings, result.sync_data.native_file, result.sync_data.cross_file)
 
     return result, settings
 

cppython/plugins/conan/builder.py

@@ -83,10 +83,11 @@ def _create_conanfile(
     ) -> None:
         """Creates a conanfile.py file that inherits from CPPython base."""
         class_name = name.replace('-', '_').title().replace('_', '')
-        content = f'''import os
-from conan.tools.cmake import CMake, CMakeDeps, CMakeToolchain
+        content = f'''from conan.tools.cmake import CMake, CMakeConfigDeps, CMakeToolchain
 from conan.tools.files import copy
 
+import os
+
 from conanfile_base import CPPythonBase
 
 
@@ -125,7 +126,7 @@ def layout(self):
         super().layout()  # Get CPPython managed layout
 
     def generate(self):
-        deps = CMakeDeps(self)
+        deps = CMakeConfigDeps(self)
         deps.generate()
         tc = CMakeToolchain(self)
         tc.user_presets_path = None
@@ -142,9 +143,11 @@ def package(self):
 
     def package_info(self):
         # Use native CMake config files to preserve FILE_SET information for C++ modules
-        # This tells CMakeDeps to skip generating files and use the package's native config
+        # This tells CMakeConfigDeps to skip generating files and use the package's native config
         self.cpp_info.set_property("cmake_find_mode", "none")
-        self.cpp_info.builddirs = ["."]
+        # Point CMakeConfigDeps to the directory containing the native config files
+        # so conan_cmakedeps_paths.cmake populates the search paths for find_package()
+        self.cpp_info.builddirs.append(os.path.join("lib", "cmake", self.name))
 
     def export_sources(self):
         copy(self, "CMakeLists.txt", src=self.recipe_folder, dst=self.export_sources_folder)

cppython/plugins/conan/plugin.py

@@ -176,6 +176,20 @@ def _run_conan_install(self, conanfile_path: Path, update: bool, build_type: str
         # Add build type setting if specified
         if build_type:
             command_args.extend(['-s', f'build_type={build_type}'])
+        # Enable CMakeConfigDeps (the modern CMake config-mode generator)
+        command_args.extend(['-c', 'tools.cmake.cmakedeps:new=will_break_next'])
+
+        # Enable 'import std;' support by providing the experimental UUID in the toolchain
+        # The UUID must be in the toolchain file (before try_compile block) so compiler
+        # detection can create __CMAKE::CXX23 for projects using 'import std;'
+        command_args.extend(
+            [
+                '-c',
+                'tools.cmake.cmaketoolchain:extra_variables={'
+                "'CMAKE_EXPERIMENTAL_CXX_IMPORT_STD': 'd0edc3af-4c50-42ea-a356-e2862fe7a444'"
+                '}',
+            ]
+        )
 
         # Add cmake binary configuration if specified
         if self._cmake_binary:
@@ -380,6 +394,30 @@ def _run_conan_create(self, conanfile_path: Path, build_type: str, logger: Logge
         command_args.extend(['-c', 'tools.graph:skip_test=True'])
         command_args.extend(['-c', 'tools.build:skip_test=True'])
 
+        # Enable CMakeConfigDeps (the modern CMake config-mode generator)
+        command_args.extend(['-c', 'tools.cmake.cmakedeps:new=will_break_next'])
+
+        # Force Ninja Multi-Config generator for C++ module support
+        # The Visual Studio generator does not support BMI-only compilation
+        # needed for consuming C++ modules across package boundaries
+        command_args.extend(['-c', 'tools.cmake.cmaketoolchain:generator=Ninja Multi-Config'])
+
+        # Enable 'import std;' support in the CMake toolchain
+        # CMAKE_EXPERIMENTAL_CXX_IMPORT_STD must be in the toolchain file (before
+        # the try_compile block) so compiler detection can create __CMAKE::CXX23.
+        # Note: CMAKE_CXX_MODULE_STD must NOT be in the toolchain because it would
+        # cause ABI detection try_compile to fail (chicken-and-egg with __CMAKE::CXX23).
+        # The UUID is specific to the CMake version and will need updating
+        # when the CMake version changes until import std graduates from experimental.
+        command_args.extend(
+            [
+                '-c',
+                'tools.cmake.cmaketoolchain:extra_variables={'
+                "'CMAKE_EXPERIMENTAL_CXX_IMPORT_STD': 'd0edc3af-4c50-42ea-a356-e2862fe7a444'"
+                '}',
+            ]
+        )
+
         # Add build type setting
         command_args.extend(['-s', f'build_type={build_type}'])
 

docs/plugins/conan/integration.md

@@ -27,7 +27,7 @@ You can customize this file for package metadata like name, version, and setting
 If you have an existing `conanfile.py`, back it up and run `cppython install` to generate both files. Then update your conanfile to inherit from `CPPythonBase`.
 
 ```python
-from conan.tools.cmake import CMake, CMakeDeps, CMakeToolchain, cmake_layout
+from conan.tools.cmake import CMake, CMakeConfigDeps, CMakeToolchain, cmake_layout
 from conanfile_base import CPPythonBase  # Import the base class
 
 

examples/conan_cmake/library/CMakeLists.txt

@@ -46,10 +46,6 @@ install(
     DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/mathutils
 )
 
-# Create empty include directory to satisfy CMake's exported target requirements
-# (module-only library with no headers, but CMake expects the directory to exist)
-install(DIRECTORY DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
-
 # Export and package configuration
 install(
     EXPORT mathutilsTargets

examples/conan_cmake/library/test_package/CMakeLists.txt

@@ -1,12 +1,8 @@
 cmake_minimum_required(VERSION 4.0)
 
-# Enable std module support for MSVC - MUST be before project()
-set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD "d0edc3af-4c50-42ea-a356-e2862fe7a444")
-
 project(MathUtilsConsumer LANGUAGES CXX)
 
-set(CMAKE_CXX_STANDARD 23)
-set(CMAKE_CXX_STANDARD_REQUIRED ON)
+# Enable 'import std;' support (requires __CMAKE::CXX23 from compiler detection)
 set(CMAKE_CXX_MODULE_STD ON)
 
 find_package(mathutils REQUIRED)

examples/conan_cmake/library/test_package/conanfile.py

@@ -4,7 +4,7 @@
 
 from conan import ConanFile
 from conan.tools.build import can_run
-from conan.tools.cmake import CMake, CMakeDeps, CMakeToolchain, cmake_layout
+from conan.tools.cmake import CMake, CMakeConfigDeps, CMakeToolchain, cmake_layout
 
 
 class MathUtilsTestConan(ConanFile):
@@ -22,7 +22,7 @@ def layout(self):
 
     def generate(self):
         """Generate CMake dependencies and toolchain."""
-        deps = CMakeDeps(self)
+        deps = CMakeConfigDeps(self)
         deps.generate()
         tc = CMakeToolchain(self)
         tc.generate()

tests/integration/examples/test_conan_cmake.py

@@ -185,6 +185,10 @@ def test_extension(example_runner: CliRunner) -> None:
         # This test uses the cppython.build backend which wraps scikit-build-core
         # The build backend automatically runs CPPython's provider workflow
 
+        # Install C++ dependencies first (creates generators/ with conan_toolchain.cmake)
+        project = TestConanCMake._create_project()
+        project.install()
+
         # Create dist directory for the wheel
         dist_path = Path('dist')
         dist_path.mkdir(exist_ok=True)