[cmake] Added find Python setup for OGS_USE_PIP.

scripts/cmake/Features.cmake

@@ -14,6 +14,11 @@ add_feature_info(
     Python-interface OGS_USE_PYTHON
     "Python boundary conditions and source terms (OGS_USE_PYTHON)"
 )
+add_feature_info(
+    Python-environment
+    OGS_USE_PIP
+    "Automatic Python dependency handling with a virtual environment (OGS_USE_PIP)"
+)
 add_feature_info(PETSc OGS_USE_PETSC "Parallel processing (OGS_USE_PETSC)")
 add_feature_info(
     Tests OGS_BUILD_TESTING "Unit and benchmarks tests (OGS_BUILD_TESTING)"

scripts/cmake/PythonCreateVirtualEnv.cmake

+# cmake-lint: disable=C0103
+message(STATUS "┌─ PythonCreateVirtualEnv.cmake")
+list(APPEND CMAKE_MESSAGE_INDENT "│    ")
+
+# Prefer unix location over frameworks (Apple-only)
+set(Python_FIND_FRAMEWORK LAST)
+
+# Prefer more recent Python version
+set(Python_FIND_STRATEGY VERSION)
+
+find_package(Python ${python_version} COMPONENTS Interpreter REQUIRED)
+
+execute_process(
+    COMMAND ${Python_EXECUTABLE} -m venv .venv
+    WORKING_DIRECTORY ${PROJECT_BINARY_DIR}
+)
+
+list(POP_BACK CMAKE_MESSAGE_INDENT)
+message(STATUS "└─ End PythonCreateVirtualEnv.cmake")

scripts/cmake/PythonSetup.cmake

 # cmake-lint: disable=C0103
 
-# Prefer unix location over frameworks (Apple-only)
-set(Python_FIND_FRAMEWORK LAST)
-
-# Prefer more recent Python version
-set(Python_FIND_STRATEGY VERSION)
-set(_python_componets Interpreter)
-if(OGS_USE_PYTHON OR OGS_USE_PIP)
+if(OGS_USE_PIP)
+    set(Python_ROOT_DIR ${PROJECT_BINARY_DIR}/.venv)
     set(CMAKE_REQUIRE_FIND_PACKAGE_Python TRUE)
+    if(NOT EXISTS ${PROJECT_BINARY_DIR}/.venv)
+        execute_process(
+            COMMAND
+                ${CMAKE_COMMAND} -DPROJECT_BINARY_DIR=${PROJECT_BINARY_DIR}
+                -Dpython_version=${ogs.minimum_version.python} -P
+                ${PROJECT_SOURCE_DIR}/scripts/cmake/PythonCreateVirtualEnv.cmake
+            WORKING_DIRECTORY ${PROJECT_BINARY_DIR} COMMAND_ECHO STDOUT
+                              ECHO_OUTPUT_VARIABLE ECHO_ERROR_VARIABLE
+        )
+        unset(_OGS_PYTHON_PACKAGES_SHA1 CACHE)
+    endif()
+else()
+    # Prefer unix location over frameworks (Apple-only)
+    set(Python_FIND_FRAMEWORK LAST)
+
+    # Prefer more recent Python version
+    set(Python_FIND_STRATEGY VERSION)
 endif()
+
+set(_python_componets Interpreter)
 if(OGS_USE_PYTHON)
+    set(CMAKE_REQUIRE_FIND_PACKAGE_Python TRUE)
     list(APPEND _python_componets Development)
 endif()
 find_package(
@@ -20,14 +35,6 @@ if(OGS_USE_PIP)
     set(OGS_PYTHON_PACKAGES ""
         CACHE INTERNAL "List of Python packages to be installed via pip."
     )
-
-    if(NOT EXISTS ${PROJECT_BINARY_DIR}/.venv)
-        execute_process(
-            COMMAND ${Python_EXECUTABLE} -m venv .venv
-            WORKING_DIRECTORY ${PROJECT_BINARY_DIR}
-        )
-        unset(_OGS_PYTHON_PACKAGES_SHA1 CACHE)
-    endif()
     set(Python_ROOT_DIR ${PROJECT_BINARY_DIR}/.venv)
     if(MSVC)
         set(Python_EXECUTABLE ${Python_ROOT_DIR}/Scripts/python.exe)