FindPython: Add capability to specify Python implementations

Through hint Python_FIND_IMPLEMENTATIONS it is possble to specify, as an
ordered list, which implementations must be searched for.
Currently possible values are:
* CPython
* IronPython

Help/release/dev/FindPython-find-implementations.rst

@@ -0,0 +1,5 @@
+FindPython-find-implementations
+-------------------------------
+
+* The :module:`FindPython3`, :module:`FindPython2` and :module:`FindPython`
+  modules gained the capability to specify which implementations to search for.

Modules/FindPython.cmake

@@ -271,6 +271,27 @@ Hints
     recommended to also include the component ``Interpreter`` to get expected
     result.
 
+``Python_FIND_IMPLEMENTATIONS``
+  This variable defines, in an ordered list, the different implementations
+  which will be searched. The ``Python_FIND_IMPLEMENTATIONS`` variable can
+  hold the following values:
+
+  * ``CPython``: this is the standard implementation. Various products, like
+    ``Anaconda`` or ``ActivePython``, rely on this implementation.
+  * ``IronPython``: This implementation use the ``CSharp`` language for
+    ``.NET Framework`` on top of the `Dynamic Language Runtime` (``DLR``).
+    See `IronPython <http://ironpython.net>`_.
+
+  The default value is the list: ``CPython``, ``IronPython``.
+
+  .. note::
+
+    This hint has the lowest priority of all hints, so even if, for example,
+    you specify ``IronPython`` first and ``CPython`` in second, a python
+    product based on ``CPython`` can be selected because, for example with
+    ``Python_FIND_STRATEGY=LOCATION``, each location will be search first for
+    ``IronPython`` and second for ``CPython``.
+
 Artifacts Specification
 ^^^^^^^^^^^^^^^^^^^^^^^
 

Modules/FindPython2.cmake

@@ -218,6 +218,27 @@ Hints
     recommended to also include the component ``Interpreter`` to get expected
     result.
 
+``Python2_FIND_IMPLEMENTATIONS``
+  This variable defines, in an ordered list, the different implementations
+  which will be searched. The ``Python2_FIND_IMPLEMENTATIONS`` variable can
+  hold the following values:
+
+  * ``CPython``: this is the standard implementation. Various products, like
+    ``Anaconda`` or ``ActivePython``, rely on this implementation.
+  * ``IronPython``: This implementation use the ``CSharp`` language for
+    ``.NET Framework`` on top of the `Dynamic Language Runtime` (``DLR``).
+    See `IronPython <http://ironpython.net>`_.
+
+  The default value is the list: ``CPython``, ``IronPython``.
+
+  .. note::
+
+    This hint has the lowest priority of all hints, so even if, for example,
+    you specify ``IronPython`` first and ``CPython`` in second, a python
+    product based on ``CPython`` can be selected because, for example with
+    ``Python2_FIND_STRATEGY=LOCATION``, each location will be search first for
+    ``IronPython`` and second for ``CPython``.
+
 Artifacts Specification
 ^^^^^^^^^^^^^^^^^^^^^^^
 

Modules/FindPython3.cmake

@@ -268,6 +268,27 @@ Hints
     recommended to also include the component ``Interpreter`` to get expected
     result.
 
+``Python3_FIND_IMPLEMENTATIONS``
+  This variable defines, in an ordered list, the different implementations
+  which will be searched. The ``Python3_FIND_IMPLEMENTATIONS`` variable can
+  hold the following values:
+
+  * ``CPython``: this is the standard implementation. Various products, like
+    ``Anaconda`` or ``ActivePython``, rely on this implementation.
+  * ``IronPython``: This implementation use the ``CSharp`` language for
+    ``.NET Framework`` on top of the `Dynamic Language Runtime` (``DLR``).
+    See `IronPython <http://ironpython.net>`_.
+
+  The default value is the list: ``CPython``, ``IronPython``.
+
+  .. note::
+
+    This hint has the lowest priority of all hints, so even if, for example,
+    you specify ``IronPython`` first and ``CPython`` in second, a python
+    product based on ``CPython`` can be selected because, for example with
+    ``Python3_FIND_STRATEGY=LOCATION``, each location will be search first for
+    ``IronPython`` and second for ``CPython``.
+
 Artifacts Specification
 ^^^^^^^^^^^^^^^^^^^^^^^
 

Tests/FindPython/CMakeLists.txt

@@ -314,6 +314,29 @@ if(CMake_TEST_FindPython_Conda)
     )
 endif()
 
+if (CMake_TEST_FindPython AND CMake_TEST_FindPython_IronPython)
+  add_test(NAME FindPython.Implementation.CPython COMMAND
+    ${CMAKE_CTEST_COMMAND} -C $<CONFIGURATION>
+    --build-and-test
+    "${CMake_SOURCE_DIR}/Tests/FindPython/Implementation"
+    "${CMake_BINARY_DIR}/Tests/FindPython/Implementation.CPython"
+    ${build_generator_args}
+    --build-project TestImplementationCPython
+    --build-options ${build_options} -DPython_REQUESTED_VERSION=2 -DPython_REQUESTED_IMPLEMENTATIONS=CPython
+    --test-command ${CMAKE_CTEST_COMMAND} -V -C $<CONFIGURATION>
+    )
+  add_test(NAME FindPython.Implementation.IronPython COMMAND
+    ${CMAKE_CTEST_COMMAND} -C $<CONFIGURATION>
+    --build-and-test
+    "${CMake_SOURCE_DIR}/Tests/FindPython/Implementation"
+    "${CMake_BINARY_DIR}/Tests/FindPython/Implementation.IronPython"
+    ${build_generator_args}
+    --build-project TestImplementationIronPython
+    --build-options ${build_options} -DPython_REQUESTED_VERSION=2 -DPython_REQUESTED_IMPLEMENTATION=IronPython
+    --test-command ${CMAKE_CTEST_COMMAND} -V -C $<CONFIGURATION>
+    )
+endif()
+
 if(CMake_TEST_FindPython_IronPython)
   add_test(NAME FindPython.IronPython2.LOCATION COMMAND
     ${CMAKE_CTEST_COMMAND} -C $<CONFIGURATION>

Tests/FindPython/Implementation/CMakeLists.txt

@@ -0,0 +1,37 @@
+cmake_minimum_required(VERSION 3.1)
+
+project(TestImplementation${Python_REQUESTED_IMPLEMENTATION} C)
+
+
+set (Python${Python_REQUESTED_VERSION}_FIND_IMPLEMENTATIONS ${Python_REQUESTED_IMPLEMENTATION})
+
+find_package(Python${Python_REQUESTED_VERSION} COMPONENTS Interpreter)
+if (NOT Python${Python_REQUESTED_VERSION}_FOUND OR NOT Python${Python_REQUESTED_VERSION}_Interpreter_FOUND)
+  message (FATAL_ERROR "Fail to found Python${Python_REQUESTED_VERSION}")
+endif()
+
+if (Python_REQUESTED_IMPLEMENTATION STREQUAL "IronPython"
+    AND NOT Python${Python_REQUESTED_VERSION}_INTERPRETER_ID STREQUAL "IronPython")
+  message (FATAL_ERROR "Erroneous interpreter ID (${Python${Python_REQUESTED_VERSION}_INTERPRETER_ID})")
+endif()
+if (Python_REQUESTED_IMPLEMENTATION STREQUAL "CPython"
+    AND Python${Python_REQUESTED_VERSION}_INTERPRETER_ID STREQUAL "IronPython")
+  message (FATAL_ERROR "Erroneous interpreter ID (${Python${Python_REQUESTED_VERSION}_INTERPRETER_ID})")
+endif()
+
+
+set (Python_FIND_IMPLEMENTATIONS ${Python_REQUESTED_IMPLEMENTATION})
+
+find_package(Python ${Python_REQUESTED_VERSION} REQUIRED COMPONENTS Interpreter)
+if (NOT Python_FOUND OR NOT Python_Interpreter_FOUND)
+  message (FATAL_ERROR "Fail to found Python ${Python_REQUESTED_VERSION}")
+endif()
+
+if (Python_REQUESTED_IMPLEMENTATION STREQUAL "IronPython"
+    AND NOT Python_INTERPRETER_ID STREQUAL "IronPython")
+  message (FATAL_ERROR "Erroneous interpreter ID (${Python_INTERPRETER_ID})")
+endif()
+if (Python_REQUESTED_IMPLEMENTATION STREQUAL "CPython"
+    AND Python_INTERPRETER_ID STREQUAL "IronPython")
+  message (FATAL_ERROR "Erroneous interpreter ID (${Python_INTERPRETER_ID})")
+endif()

Tests/FindPython/IronPython/CMakeLists.txt

@@ -2,11 +2,20 @@ cmake_minimum_required(VERSION 3.1)
 
 project(TestIronPython C)
 
-find_package(Python ${Python_REQUESTED_VERSION} REQUIRED COMPONENTS Interpreter Compiler)
+set (Python_FIND_IMPLEMENTATIONS IronPython)
+
+find_package(Python ${Python_REQUESTED_VERSION} COMPONENTS Interpreter Compiler)
 if (NOT Python_FOUND)
   message (FATAL_ERROR "Fail to found Python ${Python_REQUESTED_VERSION}")
 endif()
 
+if (NOT Python_Interpreter_FOUND)
+  message (FATAL_ERROR "Fail to found Python Interpreter")
+endif()
+if (NOT Python_INTERPRETER_ID STREQUAL "IronPython")
+  message (FATAL_ERROR "Erroneous interpreter ID (${Python_INTERPRETER_ID})")
+endif()
+
 if (NOT Python_Compiler_FOUND)
   message (FATAL_ERROR "Fail to found Python Compiler")
 endif()

Tests/FindPython/IronPython2/CMakeLists.txt

@@ -2,11 +2,20 @@ cmake_minimum_required(VERSION 3.1)
 
 project(TestIronPython2 C)
 
-find_package(Python2 REQUIRED COMPONENTS Interpreter Compiler)
+set (Python2_FIND_IMPLEMENTATIONS "IronPython")
+
+find_package(Python2 COMPONENTS Interpreter Compiler)
 if (NOT Python2_FOUND)
   message (FATAL_ERROR "Fail to found Python 2")
 endif()
 
+if (NOT Python2_Interpreter_FOUND)
+  message (FATAL_ERROR "Fail to found Python 2 Interpreter")
+endif()
+if (NOT Python2_INTERPRETER_ID STREQUAL "IronPython")
+  message (FATAL_ERROR "Erroneous interpreter ID (${Python2_INTERPRETER_ID})")
+endif()
+
 if (NOT Python2_Compiler_FOUND)
   message (FATAL_ERROR "Fail to found Python 2 Compiler")
 endif()