Attempt to keep build behind flag

Author: spacey-sooty

trajoptlib/CMakeLists.txt

@@ -63,6 +63,7 @@ option(BUILD_SHARED_LIBS "Build using shared libraries" ON)
 set(CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS FALSE)
 
 option(BUILD_EXAMPLES "Build examples" OFF)
+option(BUILD_PYTHON "Build Python" OFF)
 
 include(CompilerFlags)
 
@@ -234,15 +235,31 @@ if(BUILD_EXAMPLES)
     endforeach()
 endif()
 
-set(DEV_MODULE Development.Module)
 
-find_package(Python 3.8 COMPONENTS Interpreter ${DEV_MODULE} REQUIRED)
 
-# Detect the installed nanobind package and import it into CMake
-execute_process(
-    COMMAND "${Python_EXECUTABLE}" -m nanobind --cmake_dir
-  OUTPUT_STRIP_TRAILING_WHITESPACE OUTPUT_VARIABLE nanobind_ROOT)
-find_package(nanobind CONFIG REQUIRED)
+if (BUILD_PYTHON)
+    set(DEV_MODULE Development.Module)
+    find_package(Python 3.8 COMPONENTS Interpreter ${DEV_MODULE} REQUIRED)
 
-nanobind_add_module(trajoptlib_py py/main.cpp)
-target_link_libraries(trajoptlib_py PUBLIC TrajoptLib)
+    # nanobind dependency
+    fetchcontent_declare(
+        nanobind
+        GIT_REPOSITORY https://github.com/wjakob/nanobind.git
+        GIT_TAG v2.6.1
+    )
+    fetchcontent_makeavailable(nanobind)
+
+    # pybind11_mkdoc dependency
+    fetchcontent_declare(
+        pybind11_mkdoc
+        GIT_REPOSITORY https://github.com/pybind/pybind11_mkdoc.git
+        # master on 2023-02-08
+        GIT_TAG 42fbf377824185e255b06d68fa70f4efcd569e2d
+        GIT_SUBMODULES ""
+    )
+    fetchcontent_makeavailable(pybind11_mkdoc)
+    include(cmake/modules/Pybind11Mkdoc.cmake)
+
+    nanobind_add_module(trajoptlib_py py/main.cpp)
+    target_link_libraries(trajoptlib_py PUBLIC TrajoptLib)
+endif()

trajoptlib/cmake/modules/Pybind11Mkdoc.cmake

@@ -0,0 +1,58 @@
+function(pybind11_mkdoc target headers)
+    find_package(Python3 REQUIRED COMPONENTS Interpreter)
+
+    if(UNIX AND NOT APPLE)
+        if(EXISTS /usr/lib/libclang.so)
+            set(env_vars
+                LLVM_DIR_PATH=/usr/lib
+                LIBCLANG_PATH=/usr/lib/libclang.so
+            )
+        else()
+            # Get default clang version
+            execute_process(
+                COMMAND
+                    bash -c
+                    "clang++ --version | grep -E -o \'[0-9]+\' | head -1"
+                OUTPUT_VARIABLE CLANG_VERSION
+                OUTPUT_STRIP_TRAILING_WHITESPACE
+                COMMAND_ERROR_IS_FATAL ANY
+            )
+
+            set(env_vars
+                LLVM_DIR_PATH=/usr/lib/llvm-${CLANG_VERSION}
+                LIBCLANG_PATH=/usr/lib/llvm-${CLANG_VERSION}/lib/libclang.so
+            )
+        endif()
+    endif()
+
+    get_target_property(target_dirs ${target} INCLUDE_DIRECTORIES)
+    list(TRANSFORM target_dirs PREPEND "-I")
+
+    get_target_property(eigen_dirs Eigen3::Eigen INTERFACE_INCLUDE_DIRECTORIES)
+    list(FILTER eigen_dirs INCLUDE REGEX "\\$<BUILD_INTERFACE:.*>")
+    list(TRANSFORM eigen_dirs PREPEND "-I")
+
+    get_target_property(
+        small_vector_dirs
+        small_vector
+        INTERFACE_INCLUDE_DIRECTORIES
+    )
+    list(FILTER small_vector_dirs INCLUDE REGEX "\\$<BUILD_INTERFACE:.*>")
+    list(TRANSFORM small_vector_dirs PREPEND "-I")
+
+    add_custom_command(
+        OUTPUT ${CMAKE_CURRENT_SOURCE_DIR}/jormungandr/cpp/docstrings.hpp
+        COMMAND
+            ${env_vars} ${Python3_EXECUTABLE} -m pybind11_mkdoc ${headers} -o
+            ${CMAKE_CURRENT_SOURCE_DIR}/jormungandr/cpp/docstrings.hpp
+            -I/usr/lib/clang/`clang++ --version | grep -E -o '[0-9]+' | head
+            -1`/include ${target_dirs} ${eigen_dirs} ${small_vector_dirs}
+            -std=c++23
+        DEPENDS ${headers}
+        USES_TERMINAL
+    )
+    add_custom_target(
+        ${target}_docstrings
+        DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/jormungandr/cpp/docstrings.hpp
+    )
+endfunction()