feat: Add support for OUTPUT parameter

src/cython_cmake/cmake/UseCython.cmake

@@ -10,6 +10,7 @@
 #   Cython_compile_pyx(<pyx_file>
 #                     [LANGUAGE C | CXX]
 #                     [CYTHON_ARGS <args> ...]
+#                     [OUTPUT <OutputFile>]
 #                     [OUTPUT_VARIABLE <OutputVariable>])
 #
 # Options:
@@ -23,10 +24,14 @@
 #   Specify additional arguments for the cythonization process. Will default to
 #   the ``CYTHON_ARGS`` variable if not specified.
 #
+# ``OUTPUT <OutputFile>``
+#   Specify a specific path for the output file as ``<OutputFile>``. By
+#   default, this will output into the current binary dir. A depfile will be
+#   created alongside this file as well.
+#
 # ``OUTPUT_VARIABLE <OutputVariable>``
 #   Set the variable ``<OutputVariable>`` in the parent scope to the path to the
-#   generated source file.  By default, ``<Name>`` is used as the output
-#   variable name.
+#   generated source file.
 #
 # Defined variables:
 #
@@ -72,7 +77,7 @@ endif()
 
 function(Cython_compile_pyx)
   set(_options )
-  set(_one_value LANGUAGE OUTPUT_VARIABLE)
+  set(_one_value LANGUAGE OUTPUT OUTPUT_VARIABLE)
   set(_multi_value CYTHON_ARGS)
 
   cmake_parse_arguments(_args
@@ -127,15 +132,9 @@ function(Cython_compile_pyx)
   set(_language_arg ${_language_${_language}_arg})
   set(_language_extension ${_language_${_language}_extension})
 
-  set(generated_files)
-
-  foreach(_source_file IN LISTS _source_files)
+  function(_compile_pyx _source_file generated_file)
 
-    # Can use cmake_path for CMake 3.20+
-    # cmake_path(GET _source_file STEM _name)
-    get_filename_component(_name "${_source_file}" NAME_WE)
 
-    set(generated_file "${CMAKE_CURRENT_BINARY_DIR}/${_name}.${_language_extension}")
     set_source_files_properties(${generated_file} PROPERTIES GENERATED TRUE)
 
     # Generated depfile is expected to have the ".dep" extension and be located along
@@ -167,9 +166,32 @@ function(Cython_compile_pyx)
       VERBATIM
       COMMENT ${comment}
     )
-    list(APPEND generated_files ${generated_file})
-  endforeach()
+  endfunction()
+
+  function(_set_output _input_file _output_var)
+    # Can use cmake_path for CMake 3.20+
+    # cmake_path(GET _input_file STEM basename)
+    get_filename_component(_basename "${_input_file}" NAME_WE)
+
+    set(${_output_var} "${CMAKE_CURRENT_BINARY_DIR}/${_basename}.${_language_extension}" PARENT_SCOPE)
+  endfunction()
+
+  set(generated_files)
+
+  list(GET _source_files 0 _source_file)
+
+  # Place the cython files in the current binary dir if no path given
+  if(NOT _args_OUTPUT)
+    _set_output(${_source_file} _args_OUTPUT)
+  elseif(NOT IS_ABSOLUTE ${_args_OUTPUT})
+    set(_args_OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/${_args_OUTPUT}")
+  endif()
+
+  set(generated_file ${_args_OUTPUT})
+  _compile_pyx(${_source_file} ${generated_file})
+  list(APPEND generated_files ${generated_file})
 
+  # Output variable only if set
   if(_args_OUTPUT_VARIABLE)
     set(_output_variable ${_args_OUTPUT_VARIABLE})
     set(${_output_variable} ${generated_files} PARENT_SCOPE)

tests/packages/simple/CMakeLists.txt

@@ -8,7 +8,11 @@ find_package(
 find_package(Cython MODULE REQUIRED VERSION 3.0)
 include(UseCython)
 
-cython_compile_pyx(simple.pyx LANGUAGE C OUTPUT_VARIABLE simple_c)
+cython_compile_pyx(simple.pyx
+  LANGUAGE C
+  # OUTPUT_ARG
+  OUTPUT_VARIABLE simple_c
+)
 
 python_add_library(simple MODULE "${simple_c}" WITH_SOABI)
 

tests/test_package.py

@@ -1,9 +1,11 @@
 from __future__ import annotations
 
 import importlib.metadata
+import shutil
 import zipfile
 from pathlib import Path
 
+import pytest
 from scikit_build_core.build import build_wheel
 
 import cython_cmake as m
@@ -15,7 +17,7 @@ def test_version():
     assert importlib.metadata.version("cython_cmake") == m.__version__
 
 
-def test_scikit_build_core(monkeypatch, tmp_path):
+def test_simple(monkeypatch, tmp_path):
     monkeypatch.chdir(DIR / "packages/simple")
     build_dir = tmp_path / "build"
 
@@ -30,3 +32,42 @@ def test_scikit_build_core(monkeypatch, tmp_path):
     build_files = {x.name for x in build_dir.iterdir()}
     assert "simple.c.dep" in build_files
     assert "simple.c" in build_files
+
+
+@pytest.mark.parametrize("output_arg", ["empty", "relative", "absolute"])
+def test_output_argument(monkeypatch, tmp_path, output_arg):
+    package_dir = tmp_path / "pkg2"
+    shutil.copytree(DIR / "packages/simple", package_dir)
+    monkeypatch.chdir(package_dir)
+
+    build_dir = tmp_path / "build"
+
+    output_values = {
+        "empty": "",
+        "relative": "relative-custom.c",
+        "absolute": (build_dir / "absolute-custom.c").as_posix(),
+    }
+
+    cmakelists = Path("CMakeLists.txt")
+    txt = cmakelists.read_text().replace(
+        "# OUTPUT_ARG", f'OUTPUT "{output_values[output_arg]}"'
+    )
+    cmakelists.write_text(txt)
+
+    wheel = build_wheel(
+        str(tmp_path), {"build-dir": str(build_dir), "wheel.license-files": []}
+    )
+
+    with zipfile.ZipFile(tmp_path / wheel) as f:
+        file_names = set(f.namelist())
+    assert len(file_names) == 4
+
+    generated_file = {
+        "empty": "simple.c",
+        "relative": "relative-custom.c",
+        "absolute": "absolute-custom.c",
+    }[output_arg]
+
+    build_files = {x.name for x in build_dir.iterdir()}
+    assert f"{generated_file}.dep" in build_files
+    assert generated_file in build_files