Fix naming of ABI3 extension libraries on Windows

This commit fixes the naming conventions of ABI3 builds on Windows. It
also adopts a recent CMake/FindPython interface whenever available.

CMakeLists.txt

@@ -55,15 +55,11 @@ endif()
 # ---------------------------------------------------------------------------
 
 if (NOT TARGET Python::Module OR NOT TARGET Python::Interpreter)
-    set(Python_FIND_FRAMEWORK LAST) # Prefer Brew/Conda to Apple framework python
+  set(Python_FIND_FRAMEWORK LAST) # Prefer Brew/Conda to Apple framework python
 
-    if (WIN32 AND CMAKE_VERSION VERSION_GREATER_EQUAL 3.26 AND Python_INTERPRETER_ID STREQUAL "Python")
-      # Windows stable ABI builds for CPython require Development.SABIModule provided by CMake>=3.26
-      find_package(Python 3.8 COMPONENTS Interpreter Development.Module Development.SABIModule REQUIRED)
-    else()
-      # The following suffices in all other cases
-      find_package(Python 3.8 COMPONENTS Interpreter Development REQUIRED)
-    endif()
+  find_package(Python 3.8
+    REQUIRED COMPONENTS Interpreter Development.Module
+    OPTIONAL_COMPONENTS Development.SABIModule)
 endif()
 
 # ---------------------------------------------------------------------------

cmake/nanobind-config.cmake

@@ -4,20 +4,40 @@ if (NOT TARGET Python::Module)
   message(FATAL_ERROR "You must invoke 'find_package(Python COMPONENTS Interpreter Development REQUIRED)' prior to including nanobind.")
 endif()
 
-# Determine the Python extension suffix and stash in the CMake cache
-execute_process(
-  COMMAND "${Python_EXECUTABLE}" "-c"
-    "import sysconfig; print(sysconfig.get_config_var('EXT_SUFFIX'))"
-  RESULT_VARIABLE NB_SUFFIX_RET
-  OUTPUT_VARIABLE NB_SUFFIX
-  OUTPUT_STRIP_TRAILING_WHITESPACE)
-
-if (NB_SUFFIX_RET AND NOT NB_SUFFIX_RET EQUAL 0)
-  message(FATAL_ERROR "nanobind: Python sysconfig query to "
-    "find 'EXT_SUFFIX' property failed!")
+# Determine the right suffix for ordinary and stable ABI extensions
+if (Python_SOSABI)
+  set(NB_SUFFIX_EXT "${CMAKE_SHARED_MODULE_SUFFIX}")
+  if (WIN32)
+    set(NB_SUFFIX_EXT ".pyd")
+  endif()
+
+  # These are guaranteed to both be available in CMake 3.26+
+  set(NB_SUFFIX   ".${Python_SOABI}${NB_SUFFIX_EXT}")
+  set(NB_SUFFIX_S ".${Python_SOSABI}${NB_SUFFIX_EXT}")
+else()
+  # Determine the Python extension suffix and stash in the CMake cache
+  execute_process(
+    COMMAND "${Python_EXECUTABLE}" "-c"
+      "import sysconfig; print(sysconfig.get_config_var('EXT_SUFFIX'))"
+    RESULT_VARIABLE NB_SUFFIX_RET
+    OUTPUT_VARIABLE NB_SUFFIX
+    OUTPUT_STRIP_TRAILING_WHITESPACE)
+
+  if (NB_SUFFIX_RET AND NOT NB_SUFFIX_RET EQUAL 0)
+    message(FATAL_ERROR "nanobind: Python sysconfig query to "
+      "find 'EXT_SUFFIX' property failed!")
+  endif()
+
+  get_filename_component(NB_SUFFIX_EXT "${NB_SUFFIX}" LAST_EXT)
+  if (WIN32)
+    set(NB_SUFFIX_S "${NB_SUFFIX_EXT}")
+  else()
+    set(NB_SUFFIX_S ".abi3${NB_SUFFIX_EXT}")
+  endif()
 endif()
 
-set(NB_SUFFIX ${NB_SUFFIX} CACHE INTERNAL "")
+set(NB_SUFFIX   ${NB_SUFFIX}   CACHE INTERNAL "")
+set(NB_SUFFIX_S ${NB_SUFFIX_S} CACHE INTERNAL "")
 
 get_filename_component(NB_DIR "${CMAKE_CURRENT_LIST_FILE}" PATH)
 get_filename_component(NB_DIR "${NB_DIR}" PATH)
@@ -194,8 +214,7 @@ function(nanobind_extension name)
 endfunction()
 
 function(nanobind_extension_abi3 name)
-  get_filename_component(ext "${NB_SUFFIX}" LAST_EXT)
-  set_target_properties(${name} PROPERTIES PREFIX "" SUFFIX ".abi3${ext}")
+  set_target_properties(${name} PROPERTIES PREFIX "" SUFFIX "${NB_SUFFIX_S}")
 endfunction()
 
 function (nanobind_lto name)
@@ -238,23 +257,10 @@ function(nanobind_add_module name)
     set(ARG_NB_STATIC TRUE)
   endif()
 
-  # Stable ABI interface requires Python >= 3.12
-  if (ARG_STABLE_ABI AND (Python_VERSION_MAJOR EQUAL 3) AND (Python_VERSION_MINOR LESS 12))
-    set(ARG_STABLE_ABI OFF)
-  endif()
-
-  # Stable API interface requires CPython (PyPy isn't supported)
-  if (ARG_STABLE_ABI AND NOT (Python_INTERPRETER_ID STREQUAL "Python"))
-    set(ARG_STABLE_ABI OFF)
-  endif()
-
-  # On Windows, use of the stable ABI requires a very recent CMake version
-  if (ARG_STABLE_API AND WIN32 AND NOT TARGET Python::SABIModule)
-    if (CMAKE_VERSION VERSION_LESS 3.26)
-      message(WARNING "To build stable ABI packages on Windows, you must use CMake version 3.26 or newer!")
-    else()
-      message(WARNING "To build stable ABI packages on Windows, you must invoke 'find_package(Python COMPONENTS Interpreter Development.Module Development.SABIModule REQUIRED)' prior to including nanobind.")
-    endif()
+  # Stable ABI builds require CPython >= 3.12 and Python::SABIModule
+  if ((Python_VERSION VERSION_LESS 3.12) OR
+      (NOT Python_INTERPRETER_ID STREQUAL "Python") OR
+      (NOT TARGET Python::SABIModule))
     set(ARG_STABLE_ABI OFF)
   endif()