From a1c15f7b20d3ca40fe1f2b1819fd8fa5a5924232 Mon Sep 17 00:00:00 2001
From: Steve Peters <scpeters@openrobotics.org>
Date: Fri, 31 May 2024 21:10:34 -0700
Subject: [PATCH] Deprecate GzPython.cmake (#431)

It's better to call find_package(Python3) directly so the
user has better control over which COMPONENTS are requested.

Update GzBuildTests.cmake and GzCodeCheck.cmake to
stop using GzPython.

Signed-off-by: Steve Peters <scpeters@openrobotics.org>
---
 Migration.md             |  3 +++
 cmake/GzBuildTests.cmake |  4 +++-
 cmake/GzCodeCheck.cmake  |  4 +++-
 cmake/GzPython.cmake     | 27 ++++-----------------------
 4 files changed, 13 insertions(+), 25 deletions(-)

diff --git a/Migration.md b/Migration.md
index 5e60c5ba..5a2fda66 100644
--- a/Migration.md
+++ b/Migration.md
@@ -19,6 +19,9 @@ release will remove the deprecated code.
    The change deprecates the HIDDEN_SYMBOLS_BY_DEFAULT flag that can be
    removed.
 
+1. **Deprecated**: `GzPython.cmake`
+    **Replacement**: Use `find_package(Python3)` to find Python3 and the
+              `Python3_EXECUTABLE` variable instead of `PYTHON_EXECUTABLE`.
 
 ## Gazebo CMake 2.X to 3.X
 
diff --git a/cmake/GzBuildTests.cmake b/cmake/GzBuildTests.cmake
index 335dc767..b86eea58 100644
--- a/cmake/GzBuildTests.cmake
+++ b/cmake/GzBuildTests.cmake
@@ -107,7 +107,9 @@ macro(gz_build_tests)
 
     # Find the Python interpreter for running the
     # check_test_ran.py script
-    include(GzPython)
+    if(NOT Python3_Interpreter_FOUND)
+      find_package(Python3 COMPONENTS Interpreter)
+    endif()
 
     # Build all the tests
     foreach(target_name ${test_list})
diff --git a/cmake/GzCodeCheck.cmake b/cmake/GzCodeCheck.cmake
index 22931cbf..dabbfcf3 100644
--- a/cmake/GzCodeCheck.cmake
+++ b/cmake/GzCodeCheck.cmake
@@ -1,7 +1,9 @@
 # Setup the codecheck target, which will run cppcheck and cppplint.
 # This function is private to gz-cmake.
 function(_gz_setup_target_for_codecheck)
-  include(GzPython)
+  if(NOT Python3_Interpreter_FOUND)
+    find_package(Python3 COMPONENTS Interpreter)
+  endif()
 
   find_program(CPPCHECK_PATH cppcheck)
   find_program(FIND_PATH find)
diff --git a/cmake/GzPython.cmake b/cmake/GzPython.cmake
index 6ce0f118..7a6f2333 100644
--- a/cmake/GzPython.cmake
+++ b/cmake/GzPython.cmake
@@ -12,31 +12,12 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-if(${CMAKE_VERSION} VERSION_GREATER_EQUAL "3.19")
-  set(GZ_PYTHON_VERSION "" CACHE STRING
-    "Specify specific Python3 version to use ('major.minor' or 'versionMin...[<]versionMax')")
+message(WARNING "GzPython is deprecated, use find_package(Python3) instead.")
 
-  find_package(Python3 ${GZ_PYTHON_VERSION} QUIET)
-elseif(${CMAKE_VERSION} VERSION_GREATER_EQUAL "3.12")
-  # no support for finding specific versions
-  find_package(Python3 QUIET)
-else()
-  # TODO: remove this block as soon as the CMake version can safely be bumped to => 3.12
-  set(GZ_PYTHON_VERSION "" CACHE STRING
-    "Specify specific Python version to use ('major.minor' or 'major')")
+set(GZ_PYTHON_VERSION "" CACHE STRING
+  "Specify specific Python3 version to use ('major.minor' or 'versionMin...[<]versionMax')")
 
-  # if not specified otherwise use Python 3
-  if(NOT GZ_PYTHON_VERSION)
-    set(GZ_PYTHON_VERSION "3")
-  endif()
-
-  find_package(PythonInterp ${GZ_PYTHON_VERSION} QUIET)
-
-  if(PYTHONINTERP_FOUND)
-    set(Python3_Interpreter_FOUND ${PYTHONINTERP_FOUND})
-    set(Python3_EXECUTABLE ${PYTHON_EXECUTABLE})
-  endif()
-endif()
+find_package(Python3 ${GZ_PYTHON_VERSION} QUIET)
 
 # Tick-tock PYTHON_EXECUTABLE until Python3_EXECUTABLE is released
 # TODO(jrivero) gz-cmake4: start the deprecation cycle of PYTHON_EXECUTABLE