feat: FindPython support

.github/workflows/ci.yml

@@ -30,10 +30,12 @@ jobs:
             python: 3.6
             arch: x64
             max-cxx-std: 17
+            args: "-DPYBIND11_NEW_PYTHON=ON"
           - runs-on: macos-latest
             python: 3.7
             arch: x64
             max-cxx-std: 17
+            args: "-DPYBIND11_NEW_PYTHON=ON"
           - runs-on: windows-2016
             python: 3.7
             arch: x86
@@ -42,6 +44,7 @@ jobs:
             python: 3.6
             arch: x64
             max-cxx-std: 17
+            args: "-DPYBIND11_NEW_PYTHON=ON"
           - runs-on: windows-latest
             python: 3.7
             arch: x64
@@ -86,6 +89,10 @@ jobs:
         python-version: ${{ matrix.python }}
         architecture: ${{ matrix.arch }}
 
+    - name: Update CMake
+      uses: jwlawson/actions-setup-cmake@v1.3
+
+
     - name: Cache wheels
       if: startsWith(runner.os, 'macOS')
       uses: actions/cache@v2
@@ -108,7 +115,7 @@ jobs:
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
         -DCMAKE_CXX_STANDARD=11
-        -DPYTHON_EXECUTABLE=$(python -c "import sys; print(sys.executable)")
+        ${{ matrix.args }}
 
     - name: Build C++11
       run: cmake --build build -j 2
@@ -130,7 +137,7 @@ jobs:
         -DDOWNLOAD_CATCH=ON
         -DDOWNLOAD_EIGEN=ON
         -DCMAKE_CXX_STANDARD=${{ matrix.max-cxx-std }}
-        -DPYTHON_EXECUTABLE=$(python -c "import sys; print(sys.executable)")
+        ${{ matrix.args }}
 
     - name: Build C++${{ matrix.max-cxx-std }}
       run: cmake --build build2 -j 2

.github/workflows/configure.yml

@@ -26,7 +26,7 @@ jobs:
         # TODO: 3.8
         - runs-on: windows-2016
           arch: x86
-          cmake: 3.11
+          cmake: 3.8
 
         - runs-on: windows-2016
           arch: x86

CMakeLists.txt

@@ -67,6 +67,9 @@ cmake_dependent_option(
   "Install pybind11 headers in Python include directory instead of default installation prefix"
   OFF "PYBIND11_INSTALL" OFF)
 
+cmake_dependent_option(PYBIND11_NEW_PYTHON "Force new findPython" OFF
+                       "NOT CMAKE_VERSION VERSION_LESS 3.12" OFF)
+
 # NB: when adding a header don't forget to also add it to setup.py
 set(PYBIND11_HEADERS
     include/pybind11/detail/class.h
@@ -118,102 +121,36 @@ endif()
 string(REPLACE "include/" "${CMAKE_CURRENT_SOURCE_DIR}/include/" PYBIND11_HEADERS
                "${PYBIND11_HEADERS}")
 
-# Classic mode
-
-include("${CMAKE_CURRENT_LIST_DIR}/tools/pybind11Tools.cmake")
-
 # Cache variables so pybind11_add_module can be used in parent projects
 set(PYBIND11_INCLUDE_DIR
     "${CMAKE_CURRENT_LIST_DIR}/include"
     CACHE INTERNAL "")
-set(PYTHON_INCLUDE_DIRS
-    ${PYTHON_INCLUDE_DIRS}
-    CACHE INTERNAL "")
-set(PYTHON_LIBRARIES
-    ${PYTHON_LIBRARIES}
-    CACHE INTERNAL "")
-set(PYTHON_MODULE_PREFIX
-    ${PYTHON_MODULE_PREFIX}
-    CACHE INTERNAL "")
-set(PYTHON_MODULE_EXTENSION
-    ${PYTHON_MODULE_EXTENSION}
-    CACHE INTERNAL "")
-set(PYTHON_VERSION_MAJOR
-    ${PYTHON_VERSION_MAJOR}
-    CACHE INTERNAL "")
-set(PYTHON_VERSION_MINOR
-    ${PYTHON_VERSION_MINOR}
-    CACHE INTERNAL "")
-set(PYTHON_IS_DEBUG
-    "${PYTHON_IS_DEBUG}"
-    CACHE INTERNAL "")
-
-if(USE_PYTHON_INCLUDE_DIR)
-  file(RELATIVE_PATH CMAKE_INSTALL_INCLUDEDIR ${CMAKE_INSTALL_PREFIX} ${PYTHON_INCLUDE_DIRS})
-endif()
 
 # Note: when creating targets, you cannot use if statements at configure time -
 # you need generator expressions, because those will be placed in the target file.
 # You can also place ifs *in* the Config.in, but not here.
 
-# Build an interface library target:
-add_library(pybind11 INTERFACE)
-add_library(pybind11::pybind11 ALIAS pybind11) # to match exported target
+# This section builds targets, but does *not* touch Python
 
-target_include_directories(
-  pybind11 ${pybind11_system} INTERFACE $<BUILD_INTERFACE:${PYBIND11_INCLUDE_DIR}>
-                                        $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>)
-# Only add Python for build - must be added during the import for config since it has to be re-discovered.
-target_include_directories(pybind11 SYSTEM INTERFACE $<BUILD_INTERFACE:${PYTHON_INCLUDE_DIRS}>)
-
-if(CMAKE_VERSION VERSION_LESS 3.13)
-  target_compile_features(pybind11 INTERFACE cxx_inheriting_constructors cxx_user_literals
-                                             cxx_right_angle_brackets)
-else()
-  # This was added in CMake 3.8, but we are keeping a consistent breaking
-  # point for the config file at 3.13. A config generated by CMake 3.13+
-  # can only be read in 3.13+ due to the SHELL usage later, so this is safe to do.
-  target_compile_features(pybind11 INTERFACE cxx_std_11)
-endif()
+# Build the headers-only target (no Python included):
+add_library(headers INTERFACE)
+add_library(pybind11::headers ALIAS headers) # to match exported target
 
-add_library(module INTERFACE)
-add_library(pybind11::module ALIAS module)
+target_include_directories(
+  headers ${pybind11_system} INTERFACE $<BUILD_INTERFACE:${PYBIND11_INCLUDE_DIR}>
+                                       $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>)
 
-target_link_libraries(module INTERFACE pybind11::pybind11)
+target_compile_features(headers INTERFACE cxx_inheriting_constructors cxx_user_literals
+                                          cxx_right_angle_brackets)
 
-# See https://github.com/Kitware/CMake/blob/master/Modules/CMakePlatformId.h.in for platform IDs
-# Note: CMake 3.15 allows $<PLATFORM_ID:Windows,Cygwin>
-target_link_libraries(
-  module
-  INTERFACE
-    "$<$<OR:$<PLATFORM_ID:Windows>,$<PLATFORM_ID:Cygwin>>:$<BUILD_INTERFACE:${PYTHON_LIBRARIES}>>")
+include("${CMAKE_CURRENT_SOURCE_DIR}/tools/pybind11Common.cmake")
 
-if(CMAKE_VERSION VERSION_LESS 3.13)
-  target_link_libraries(module INTERFACE "$<$<PLATFORM_ID:Darwin>:-undefined dynamic_lookup>")
-else()
-  # SHELL (3.12+) forces this to remain together, and link_options was added in 3.13+
-  # This is safer, because you are ensured the deduplication pass in CMake will not consider
-  # these separate and remove one but not the other.
-  target_link_options(module INTERFACE "$<$<PLATFORM_ID:Darwin>:SHELL:-undefined dynamic_lookup>")
+if(USE_PYTHON_INCLUDE_DIR AND DEFINED Python_INCLUDE_DIRS)
+  file(RELATIVE_PATH CMAKE_INSTALL_INCLUDEDIR ${CMAKE_INSTALL_PREFIX} ${Python_INCLUDE_DIRS})
+elseif(USE_PYTHON_INCLUDE_DIR AND DEFINED PYTHON_INCLUDE_DIR)
+  file(RELATIVE_PATH CMAKE_INSTALL_INCLUDEDIR ${CMAKE_INSTALL_PREFIX} ${PYTHON_INCLUDE_DIRS})
 endif()
 
-# Workaround for Python 2.7 and C++17 (C++14 as a warning) incompatibility
-# This adds the flags -Wno-register and -Wno-deprecated-register if the compiler
-# is Clang 3.9+ or AppleClang and the compile language is CXX, or /wd5033 for MSVC (all languages,
-# since MSVC didn't recognize COMPILE_LANGUAGE until CMake 3.11+).
-set(clang_4plus
-    "$<AND:$<CXX_COMPILER_ID:Clang>,$<NOT:$<VERSION_LESS:$<CXX_COMPILER_VERSION>,3.9>>>")
-set(no_register "$<OR:${clang_4plus},$<CXX_COMPILER_ID:AppleClang>>")
-set(cxx_no_register "$<AND:$<COMPILE_LANGUAGE:CXX>,${no_register}>")
-set(msvc "$<CXX_COMPILER_ID:MSVC>")
-target_compile_options(
-  pybind11 INTERFACE "$<${cxx_no_register}:-Wno-register;-Wno-deprecated-register>"
-                     "$<${msvc}:/wd5033>")
-
-add_library(embed INTERFACE)
-add_library(pybind11::embed ALIAS embed)
-target_link_libraries(embed INTERFACE pybind11::pybind11 $<BUILD_INTERFACE:${PYTHON_LIBRARIES}>)
-
 if(PYBIND11_INSTALL)
   install(DIRECTORY ${PYBIND11_INCLUDE_DIR}/pybind11 DESTINATION ${CMAKE_INSTALL_INCLUDEDIR})
   # GNUInstallDirs "DATADIR" wrong here; CMake search path wants "share".
@@ -248,14 +185,17 @@ if(PYBIND11_INSTALL)
   install(
     FILES ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}Config.cmake
           ${CMAKE_CURRENT_BINARY_DIR}/${PROJECT_NAME}ConfigVersion.cmake
-          tools/FindPythonLibsNew.cmake tools/pybind11Tools.cmake
+          tools/FindPythonLibsNew.cmake
+          tools/pybind11Common.cmake
+          tools/pybind11Tools.cmake
+          tools/pybind11NewTools.cmake
     DESTINATION ${PYBIND11_CMAKECONFIG_INSTALL_DIR})
 
   if(NOT PYBIND11_EXPORT_NAME)
     set(PYBIND11_EXPORT_NAME "${PROJECT_NAME}Targets")
   endif()
 
-  install(TARGETS pybind11 module embed EXPORT "${PYBIND11_EXPORT_NAME}")
+  install(TARGETS headers EXPORT "${PYBIND11_EXPORT_NAME}")
 
   install(
     EXPORT "${PYBIND11_EXPORT_NAME}"