fix: support CMake 3.27, drop 3.4

Signed-off-by: Henry Schreiner <[email protected]>

Author: henryiii

.github/workflows/configure.yml

@@ -26,20 +26,24 @@ jobs:
       matrix:
         runs-on: [ubuntu-20.04, macos-latest, windows-latest]
         arch: [x64]
-        cmake: ["3.23"]
+        cmake: ["3.26"]
 
         include:
         - runs-on: ubuntu-20.04
           arch: x64
-          cmake: 3.4
+          cmake: "3.4"
+
+        - runs-on: ubuntu-20.04
+          arch: x64
+          cmake: "3.27"
 
         - runs-on: macos-latest
           arch: x64
-          cmake: 3.7
+          cmake: "3.7"
 
         - runs-on: windows-2019
           arch: x64 # x86 compilers seem to be missing on 2019 image
-          cmake: 3.18
+          cmake: "3.18"
 
     name: 🐍 3.7 • CMake ${{ matrix.cmake }} • ${{ matrix.runs-on }}
     runs-on: ${{ matrix.runs-on }}

CMakeLists.txt

@@ -5,15 +5,15 @@
 # All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
-cmake_minimum_required(VERSION 3.4)
+cmake_minimum_required(VERSION 3.5)
 
-# The `cmake_minimum_required(VERSION 3.4...3.22)` syntax does not work with
+# The `cmake_minimum_required(VERSION 3.5...3.26)` syntax does not work with
 # some versions of VS that have a patched CMake 3.11. This forces us to emulate
 # the behavior using the following workaround:
-if(${CMAKE_VERSION} VERSION_LESS 3.22)
+if(${CMAKE_VERSION} VERSION_LESS 3.26)
   cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
 else()
-  cmake_policy(VERSION 3.22)
+  cmake_policy(VERSION 3.26)
 endif()
 
 # Avoid infinite recursion if tests include this as a subdirectory

docs/faq.rst

@@ -284,7 +284,8 @@ There are three possible solutions:
    COMPONENTS Interpreter Development)`` on modern CMake (3.12+, 3.15+ better,
    3.18.2+ best). Pybind11 in these cases uses the new CMake FindPython instead
    of the old, deprecated search tools, and these modules are much better at
-   finding the correct Python.
+   finding the correct Python. If FindPythonLibs/Interp are not available
+   (CMake 3.27+), then this will be ignored and FindPython will be used.
 3. Set ``PYBIND11_NOPYTHON`` to ``TRUE``. Pybind11 will not search for Python.
    However, you will have to use the target-based system, and do more setup
    yourself, because it does not know about or include things that depend on

tests/CMakeLists.txt

@@ -5,20 +5,17 @@
 # All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
-cmake_minimum_required(VERSION 3.4)
+cmake_minimum_required(VERSION 3.5)
 
-# The `cmake_minimum_required(VERSION 3.4...3.18)` syntax does not work with
+# The `cmake_minimum_required(VERSION 3.5...3.26)` syntax does not work with
 # some versions of VS that have a patched CMake 3.11. This forces us to emulate
 # the behavior using the following workaround:
-if(${CMAKE_VERSION} VERSION_LESS 3.21)
+if(${CMAKE_VERSION} VERSION_LESS 3.26)
   cmake_policy(VERSION ${CMAKE_MAJOR_VERSION}.${CMAKE_MINOR_VERSION})
 else()
-  cmake_policy(VERSION 3.21)
+  cmake_policy(VERSION 3.26)
 endif()
 
-# Only needed for CMake < 3.5 support
-include(CMakeParseArguments)
-
 # Filter out items; print an optional message if any items filtered. This ignores extensions.
 #
 # Usage:

tests/test_cmake_build/CMakeLists.txt

@@ -1,6 +1,3 @@
-# Built-in in CMake 3.5+
-include(CMakeParseArguments)
-
 add_custom_target(test_cmake_build)
 
 function(pybind11_add_build_test name)

tools/pybind11Common.cmake

@@ -163,11 +163,14 @@ endif()
 
 # --------------------- Python specifics -------------------------
 
+cmake_policy(GET CMP0148 _pybind11_missing_old_python)
+
 # Check to see which Python mode we are in, new, old, or no python
 if(PYBIND11_NOPYTHON)
   set(_pybind11_nopython ON)
 elseif(
-  PYBIND11_FINDPYTHON
+  _pybind11_missing_old_python STREQUAL "NEW"
+  OR PYBIND11_FINDPYTHON
   OR Python_FOUND
   OR Python2_FOUND
   OR Python3_FOUND)

tools/pybind11Config.cmake.in

@@ -63,7 +63,9 @@ Modes
 
 There are two modes provided; classic, which is built on the old Python
 discovery packages in CMake, or the new FindPython mode, which uses FindPython
-from 3.12+ forward (3.15+ _highly_ recommended).
+from 3.12+ forward (3.15+ _highly_ recommended). If you set the minimum or
+maximum version of CMake to 3.27+, then FindPython is the default (since
+FindPythonInterp/FindPythonLibs has been removed via policy `CMP0148`).
 
 New FindPython mode
 ^^^^^^^^^^^^^^^^^^^