Find pybind11 in just one place

Moves find_package(pybind11) call to src/python_pybind11
folder. When invoked through the root CMakeLists.txt,
it treats pybind11 as an optional dependency, but when
invoked from that folder, it treats it as required by
setting CMAKE_REQUIRE_FIND_PACKAGE_pybind11 to TRUE.

Signed-off-by: Steve Peters <scpeters@openrobotics.org>

CMakeLists.txt

@@ -105,16 +105,6 @@ else()
   )
   if (NOT Python3_Development_FOUND)
     GZ_BUILD_WARNING("Python development libraries are missing: Python interfaces are disabled.")
-  else()
-    set(PYBIND11_PYTHON_VERSION 3)
-    find_package(pybind11 2.2 QUIET)
-
-    if (${pybind11_FOUND})
-      message (STATUS "Searching for pybind11 - found version ${pybind11_VERSION}.")
-    else()
-      GZ_BUILD_WARNING("pybind11 is missing: Python interfaces are disabled.")
-      message (STATUS "Searching for pybind11 - not found.")
-    endif()
   endif()
 endif()
 

src/CMakeLists.txt

@@ -18,7 +18,7 @@ gz_build_tests(TYPE UNIT SOURCES ${gtest_sources})
 add_subdirectory(graph)
 
 # Bindings subdirectories
-if (pybind11_FOUND AND NOT SKIP_PYBIND11)
+if (Python3_Development_FOUND AND NOT SKIP_PYBIND11)
   add_subdirectory(python_pybind11)
 endif()
 

src/python_pybind11/CMakeLists.txt

@@ -3,14 +3,25 @@ if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
   cmake_minimum_required(VERSION 3.22.1)
   set(GZ_MATH_VER 8)
   project(gz-math${GZ_MATH_VER}-python VERSION ${GZ_MATH_VER})
-  find_package(Python3 COMPONENTS Interpreter Development REQUIRED)
-  find_package(pybind11 REQUIRED)
   find_package(gz-math${PROJECT_VERSION_MAJOR} REQUIRED)
   set(PROJECT_LIBRARY_TARGET_NAME "gz-math${PROJECT_VERSION_MAJOR}::gz-math${PROJECT_VERSION_MAJOR}")
+  # require python dependencies to be found
+  find_package(Python3 COMPONENTS Interpreter Development REQUIRED)
+  set(CMAKE_REQUIRE_FIND_PACKAGE_pybind11 TRUE)
   include(GNUInstallDirs)
   include(CTest)
 endif()
 
+set(PYBIND11_PYTHON_VERSION 3)
+find_package(pybind11 2.2 QUIET)
+
+if (${pybind11_FOUND})
+  message(STATUS "Searching for pybind11 - found version ${pybind11_VERSION}.")
+else()
+  message(WARNING "pybind11 is missing: Python interfaces are disabled.")
+  return()
+endif()
+
 message(STATUS "Building pybind11 interfaces")
 set(BINDINGS_MODULE_NAME "math${PROJECT_VERSION_MAJOR}")
 # Split from main extension and converted to pybind11