Modules/FindPython.cmake

# Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
# file Copyright.txt or https://cmake.org/licensing for details.

#[=======================================================================[.rst:
FindPython
----------

Find Python interpreter, compiler and development environment (include
directories and libraries).

The following components are supported:

* ``Interpreter``: search for Python interpreter.
* ``Compiler``: search for Python compiler. Only offered by IronPython.
* ``Development``: search for development artifacts (include directories and
  libraries).
* ``NumPy``: search for NumPy include directories.

If no ``COMPONENTS`` are specified, ``Interpreter`` is assumed.

To ensure consistent versions between components ``Interpreter``, ``Compiler``,
``Development`` and ``NumPy``, specify all components at the same time::

  find_package (Python COMPONENTS Interpreter Development)

This module looks preferably for version 3 of Python. If not found, version 2
is searched.
To manage concurrent versions 3 and 2 of Python, use :module:`FindPython3` and
:module:`FindPython2` modules rather than this one.

.. note::

  If components ``Interpreter`` and ``Development`` are both specified, this
  module search only for interpreter with same platform architecture as the one
  defined by ``CMake`` configuration. This contraint does not apply if only
  ``Interpreter`` component is specified.

Imported Targets
^^^^^^^^^^^^^^^^

This module defines the following :ref:`Imported Targets <Imported Targets>`
(when :prop_gbl:`CMAKE_ROLE` is ``PROJECT``):

``Python::Interpreter``
  Python interpreter. Target defined if component ``Interpreter`` is found.
``Python::Compiler``
  Python compiler. Target defined if component ``Compiler`` is found.
``Python::Python``
  Python library for Python embedding. Target defined if component
  ``Development`` is found.
``Python::Module``
  Python library for Python module. Target defined if component ``Development``
  is found.
``Python::NumPy``
  NumPy Python library. Target defined if component ``NumPy`` is found.

Result Variables
^^^^^^^^^^^^^^^^

This module will set the following variables in your project
(see :ref:`Standard Variable Names <CMake Developer Standard Variable Names>`):

``Python_FOUND``
  System has the Python requested components.
``Python_Interpreter_FOUND``
  System has the Python interpreter.
``Python_EXECUTABLE``
  Path to the Python interpreter.
``Python_INTERPRETER_ID``
  A short string unique to the interpreter. Possible values include:
    * Python
    * ActivePython
    * Anaconda
    * Canopy
    * IronPython
``Python_STDLIB``
  Standard platform independent installation directory.

  Information returned by
  ``distutils.sysconfig.get_python_lib(plat_specific=False,standard_lib=True)``.
``Python_STDARCH``
  Standard platform dependent installation directory.

  Information returned by
  ``distutils.sysconfig.get_python_lib(plat_specific=True,standard_lib=True)``.
``Python_SITELIB``
  Third-party platform independent installation directory.

  Information returned by
  ``distutils.sysconfig.get_python_lib(plat_specific=False,standard_lib=False)``.
``Python_SITEARCH``
  Third-party platform dependent installation directory.

  Information returned by
  ``distutils.sysconfig.get_python_lib(plat_specific=True,standard_lib=False)``.
``Python_SOABI``
  Extension suffix for modules.

  Information returned by
  ``distutils.sysconfig.get_config_flag('SOABI')`` or computed from
  ``distutils.sysconfig.get_config_flag('EXT_SUFFIX')`` or
  ``python-config --extension-suffix``.
``Python_Compiler_FOUND``
  System has the Python compiler.
``Python_COMPILER``
  Path to the Python compiler. Only offered by IronPython.
``Python_COMPILER_ID``
  A short string unique to the compiler. Possible values include:
    * IronPython
``Python_Development_FOUND``
  System has the Python development artifacts.
``Python_INCLUDE_DIRS``
  The Python include directories.
``Python_LIBRARIES``
  The Python libraries.
``Python_LIBRARY_DIRS``
  The Python library directories.
``Python_RUNTIME_LIBRARY_DIRS``
  The Python runtime library directories.
``Python_VERSION``
  Python version.
``Python_VERSION_MAJOR``
  Python major version.
``Python_VERSION_MINOR``
  Python minor version.
``Python_VERSION_PATCH``
  Python patch version.
``Python_NumPy_FOUND``
  System has the NumPy.
``Python_NumPy_INCLUDE_DIRS``
  The NumPy include directries.
``Python_NumPy_VERSION``
  The NumPy version.

Hints
^^^^^

``Python_ROOT_DIR``
  Define the root directory of a Python installation.

``Python_USE_STATIC_LIBS``
  * If not defined, search for shared libraries and static libraries in that
    order.
  * If set to TRUE, search **only** for static libraries.
  * If set to FALSE, search **only** for shared libraries.

``Python_FIND_ABI``
  This variable defines which ABIs, as defined in
  `PEP 3149 <https://www.python.org/dev/peps/pep-3149/>`_, should be searched.

  .. note::

    This hint will be honored only when searched for ``Python`` version 3.

  .. note::

    If ``Python_FIND_ABI`` is not defined, any ABI will be searched.

  The ``Python_FIND_ABI`` variable is a 3-tuple specifying, in that order,
  ``pydebug`` (``d``), ``pymalloc`` (``m``) and ``unicode`` (``u``) flags.
  Each element can be set to one of the following:

  * ``ON``: Corresponding flag is selected.
  * ``OFF``: Corresponding flag is not selected.
  * ``ANY``: The two posibilties (``ON`` and ``OFF``) will be searched.

  From this 3-tuple, various ABIs will be searched starting from the most
  specialized to the most general. Moreover, ``debug`` versions will be
  searched **after** ``non-debug`` ones.

  For example, if we have::

    set (Python_FIND_ABI "ON" "ANY" "ANY")

  The following flags combinations will be appended, in that order, to the
  artifact names: ``dmu``, ``dm``, ``du``, and ``d``.

  And to search any possible ABIs::

    set (Python_FIND_ABI "ANY" "ANY" "ANY")

  The following combinations, in that order, will be used: ``mu``, ``m``,
  ``u``, ``<empty>``, ``dmu``, ``dm``, ``du`` and ``d``.

  .. note::

    This hint is useful only on ``POSIX`` systems. So, on ``Windows`` systems,
    when ``Python_FIND_ABI`` is defined, ``Python`` distributions from
    `python.org <https://www.python.org/>`_ will be found only if value for
    each flag is ``OFF`` or ``ANY``.

``Python_FIND_STRATEGY``
  This variable defines how lookup will be done.
  The ``Python_FIND_STRATEGY`` variable can be set to one of the following:

  * ``VERSION``: Try to find the most recent version in all specified
    locations.
    This is the default if policy :policy:`CMP0094` is undefined or set to
    ``OLD``.
  * ``LOCATION``: Stops lookup as soon as a version satisfying version
    constraints is founded.
    This is the default if policy :policy:`CMP0094` is set to ``NEW``.

``Python_FIND_REGISTRY``
  On Windows the ``Python_FIND_REGISTRY`` variable determine the order
  of preference between registry and environment variables.
  the ``Python_FIND_REGISTRY`` variable can be set to one of the following:

  * ``FIRST``: Try to use registry before environment variables.
    This is the default.
  * ``LAST``: Try to use registry after environment variables.
  * ``NEVER``: Never try to use registry.

``Python_FIND_FRAMEWORK``
  On macOS the ``Python_FIND_FRAMEWORK`` variable determine the order of
  preference between Apple-style and unix-style package components.
  This variable can take same values as :variable:`CMAKE_FIND_FRAMEWORK`
  variable.

  .. note::

    Value ``ONLY`` is not supported so ``FIRST`` will be used instead.

  If ``Python_FIND_FRAMEWORK`` is not defined, :variable:`CMAKE_FIND_FRAMEWORK`
  variable will be used, if any.

``Python_FIND_VIRTUALENV``
  This variable defines the handling of virtual environments managed by
  ``virtualenv`` or ``conda``. It is meaningful only when a virtual environment
  is active (i.e. the ``activate`` script has been evaluated). In this case, it
  takes precedence over ``Python_FIND_REGISTRY`` and ``CMAKE_FIND_FRAMEWORK``
  variables.  The ``Python_FIND_VIRTUALENV`` variable can be set to one of the
  following:

  * ``FIRST``: The virtual environment is used before any other standard
    paths to look-up for the interpreter. This is the default.
  * ``ONLY``: Only the virtual environment is used to look-up for the
    interpreter.
  * ``STANDARD``: The virtual environment is not used to look-up for the
    interpreter. In this case, variable ``Python_FIND_REGISTRY`` (Windows)
    or ``CMAKE_FIND_FRAMEWORK`` (macOS) can be set with value ``LAST`` or
    ``NEVER`` to select preferably the interpreter from the virtual
    environment.

  .. note::

    If the component ``Development`` is requested, it is **strongly**
    recommended to also include the component ``Interpreter`` to get expected
    result.

Artifacts Specification
^^^^^^^^^^^^^^^^^^^^^^^

To solve special cases, it is possible to specify directly the artifacts by
setting the following variables:

``Python_EXECUTABLE``
  The path to the interpreter.

``Python_COMPILER``
  The path to the compiler.

``Python_LIBRARY``
  The path to the library. It will be used to compute the
  variables ``Python_LIBRARIES``, ``Python_LIBRAY_DIRS`` and
  ``Python_RUNTIME_LIBRARY_DIRS``.

``Python_INCLUDE_DIR``
  The path to the directory of the ``Python`` headers. It will be used to
  compute the variable ``Python_INCLUDE_DIRS``.

``Python_NumPy_INCLUDE_DIR``
  The path to the directory of the ``NumPy`` headers. It will be used to
  compute the variable ``Python_NumPy_INCLUDE_DIRS``.

.. note::

  All paths must be absolute. Any artifact specified with a relative path
  will be ignored.

.. note::

  When an artifact is specified, all ``HINTS`` will be ignored and no search
  will be performed for this artifact.

  If more than one artifact is specified, it is the user's responsability to
  ensure the consistency of the various artifacts.

By default, this module supports multiple calls in different directories of a
project with different version/component requirements while providing correct
and consistent results for each call. To support this behavior, ``CMake`` cache
is not used in the traditional way which can be problematic for interactive
specification. So, to enable also interactive specification, module behavior
can be controled with the following variable:

``Python_ARTIFACTS_INTERACTIVE``
  Selects the behavior of the module. This is a boolean variable:

  * If set to ``TRUE``: Create CMake cache entries for the above artifact
    specification variables so that users can edit them interactively.
    This disables support for multiple version/component requirements.
  * If set to ``FALSE`` or undefined: Enable multiple version/component
    requirements.

Commands
^^^^^^^^

This module defines the command ``Python_add_library`` (when
:prop_gbl:`CMAKE_ROLE` is ``PROJECT``), which has the same semantics as
:command:`add_library` and adds a dependency to target ``Python::Python`` or,
when library type is ``MODULE``, to target ``Python::Module`` and takes care of
Python module naming rules::

  Python_add_library (<name> [STATIC | SHARED | MODULE [WITH_SOABI]]
                      <source1> [<source2> ...])

If the library type is not specified, ``MODULE`` is assumed.

For ``MODULE`` library type, if option ``WITH_SOABI`` is specified, the
module suffix will include the ``Python_SOABI`` value, if any.
#]=======================================================================]


set (_PYTHON_PREFIX Python)

if (DEFINED Python_FIND_VERSION)
  set (_Python_REQUIRED_VERSION_MAJOR ${Python_FIND_VERSION_MAJOR})

  include (${CMAKE_CURRENT_LIST_DIR}/FindPython/Support.cmake)
else()
  # iterate over versions in quiet and NOT required modes to avoid multiple
  # "Found" messages and prematurally failure.
  set (_Python_QUIETLY ${Python_FIND_QUIETLY})
  set (_Python_REQUIRED ${Python_FIND_REQUIRED})
  set (Python_FIND_QUIETLY TRUE)
  set (Python_FIND_REQUIRED FALSE)

  set (_Python_REQUIRED_VERSIONS 3 2)
  set (_Python_REQUIRED_VERSION_LAST 2)

  unset (_Python_INPUT_VARS)
  foreach (_Python_ITEM IN ITEMS Python_EXECUTABLE Python_COMPILER Python_LIBRARY
                                 Python_INCLUDE_DIR Python_NumPy_INCLUDE_DIR)
    if (NOT DEFINED ${_Python_ITEM})
      list (APPEND _Python_INPUT_VARS ${_Python_ITEM})
    endif()
  endforeach()

  foreach (_Python_REQUIRED_VERSION_MAJOR IN LISTS _Python_REQUIRED_VERSIONS)
    set (Python_FIND_VERSION ${_Python_REQUIRED_VERSION_MAJOR})
    include (${CMAKE_CURRENT_LIST_DIR}/FindPython/Support.cmake)
    if (Python_FOUND OR
        _Python_REQUIRED_VERSION_MAJOR EQUAL _Python_REQUIRED_VERSION_LAST)
      break()
    endif()
    # clean-up INPUT variables not set by the user
    foreach (_Python_ITEM IN LISTS _Python_INPUT_VARS)
      unset (${_Python_ITEM})
    endforeach()
    # clean-up some CACHE variables to ensure look-up restart from scratch
    foreach (_Python_ITEM IN LISTS _Python_CACHED_VARS)
      unset (${_Python_ITEM} CACHE)
    endforeach()
  endforeach()

  unset (Python_FIND_VERSION)

  set (Python_FIND_QUIETLY ${_Python_QUIETLY})
  set (Python_FIND_REQUIRED ${_Python_REQUIRED})
  if (Python_FIND_REQUIRED OR NOT Python_FIND_QUIETLY)
    # call again validation command to get "Found" or error message
    find_package_handle_standard_args (Python HANDLE_COMPONENTS
                                              REQUIRED_VARS ${_Python_REQUIRED_VARS}
                                              VERSION_VAR Python_VERSION)
  endif()
endif()

if (COMMAND __Python_add_library)
  macro (Python_add_library)
    __Python_add_library (Python ${ARGV})
  endmacro()
endif()

unset (_PYTHON_PREFIX)