fix: try supporting older CMake

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

Author: henryiii

.github/workflows/ci.yml

@@ -51,6 +51,9 @@ jobs:
           - python-version: "3.9"
             runs-on: ubuntu-latest
             cmake: "3.20.x"
+          - python-version: "3.10"
+            runs-on: ubuntu-latest
+            cmake: "3.15.x"
 
     steps:
       - uses: actions/checkout@v4
@@ -67,6 +70,9 @@ jobs:
         with:
           cmake-version: ${{ matrix.cmake }}
 
+      - run: pipx install ninja
+        if: matrix.cmake == '3.15.x'
+
       - uses: yezz123/setup-uv@v4
 
       - name: Install package

src/cython_cmake/cmake/FindCython.cmake

@@ -18,6 +18,8 @@
 #  ``Cython::Cython``
 #    The Cython executable
 #
+# A range of versions is supported on CMake 3.19+.
+#
 # For more information on the Cython project, see https://cython.org/.
 #
 # *Cython is a language that makes writing C extensions for the Python language
@@ -39,10 +41,6 @@
 # limitations under the License.
 #=============================================================================
 
-if(CMAKE_VERSION VERSION_LESS "3.20")
-  message(SEND_ERROR "CMake 3.20 required")
-endif()
-
 # Use the Cython executable that lives next to the Python executable
 # if it is a local installation.
 if(Python_EXECUTABLE)
@@ -88,11 +86,19 @@ if(CYTHON_EXECUTABLE)
 endif()
 
 include(FindPackageHandleStandardArgs)
-find_package_handle_standard_args(Cython
-  REQUIRED_VARS CYTHON_EXECUTABLE
-  VERSION_VAR ${CYTHON_VERSION}
-  HANDLE_VERSION_RANGE
-)
+
+if(CMAKE_VERSION VERSION_LESS 3.19)
+  find_package_handle_standard_args(Cython
+    REQUIRED_VARS CYTHON_EXECUTABLE
+    VERSION_VAR ${CYTHON_VERSION}
+  )
+else()
+  find_package_handle_standard_args(Cython
+    REQUIRED_VARS CYTHON_EXECUTABLE
+    VERSION_VAR ${CYTHON_VERSION}
+    HANDLE_VERSION_RANGE
+  )
+endif()
 
 if(CYTHON_FOUND)
   if(NOT DEFINED Cython::Cython)

src/cython_cmake/cmake/UseCython.cmake

@@ -72,8 +72,8 @@
 # limitations under the License.
 #=============================================================================
 
-if(CMAKE_VERSION VERSION_LESS "3.20")
-  message(FATAL_ERROR "CMake 3.20 required")
+if(CMAKE_VERSION VERSION_LESS "3.7")
+  message(SEND_ERROR "CMake 3.7 required for DEPFILE")
 endif()
 
 
@@ -124,14 +124,21 @@ function(Cython_compile_pyx)
   endif()
 
   # Place the cython files in the current binary dir if no path given
+  # Can use cmake_path for CMake 3.20+
   if(NOT CYTHON_OUTPUT)
-    cmake_path(GET INPUT STEM basename)
-    cmake_path(APPEND CMAKE_CURRENT_BINARY_DIR "${basename}${langauge_ext}" OUTPUT_VARIABLE CYTHON_OUTPUT)
+    # cmake_path(GET INPUT STEM basename)
+    get_filename_component(basename "${INPUT}" NAME_WE)
+
+    # cmake_path(APPEND CMAKE_CURRENT_BINARY_DIR "${basename}${langauge_ext}" OUTPUT_VARIABLE CYTHON_OUTPUT)
+    set(CYTHON_OUPUT "${CMAKE_CURRENT_BINARY_DIR}/${basename}${langauge_ext}")
   endif()
-  cmake_path(ABSOLUTE_PATH CYTHON_OUTPUT)
+
+  # cmake_path(ABSOLUTE_PATH CYTHON_OUTPUT)
+  get_filename_component(CYTHON_OUTPUT "${CYTHON_OUPUT}" ABSOLUTE)
 
   # Normalize the input path
-  cmake_path(ABSOLUTE_PATH INPUT)
+  # cmake_path(ABSOLUTE_PATH INPUT)
+  get_filename_component(INPUT "${INPUT}" ABSOLUTE)
   set_source_files_properties("${INPUT}" PROPERTIES GENERATED TRUE)
 
   # Support

tests/packages/simple/CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.20...3.29)
+cmake_minimum_required(VERSION 3.15...3.29)
 project(${SKBUILD_PROJECT_NAME} LANGUAGES C)
 
 find_package(