Modernize cmake build

Add a CMake super project that includes the shiboken2, PySide2 and
pyside2-tools subprojects, so that it's possible to build everything
from Qt Creator (or any other IDE that supports CMake)
with minimal set up effort, and thus inform the IDE CMake integration
of all relevant files, for easier code editing, navigation and
refactoring.

This also lays the foundation for allowing 3rd parties to use the
shiboken2 generator to generate custom modules. This is
achieved by eliminating various hardcoded paths for libraries and
include directories.

Start using CMake targets throughout the build code to correctly
propagate link flags and include dirs for libshiboken and
shiboken2 executable targets. Same for the libpyside target.

Generate two separate cmake config files (build-tree / install-tree)
that can be used with find_package(Shiboken2), to make sure that
the PySide2 project can be built as part of the super project build.
This is currently the only way I've found to allow the super build
to work.
Note that for the build-tree find_package() to work, the
CMAKE_MODULE_PATH has to be adjusted in the super project file.

The generated config files contain variables and logic that allow
usage of the installed shiboken package in downstream projects
(PySide2). This involves things like getting the includes and
libraries for the currently found python interpreter, the shiboken
build type (release or debug), was shiboken built with limited
api support, etc.

Generate 2 separate (build-tree and install-tree) config files
for PySide2, similar to how it's done for the shiboken case, for
pyside2-tools to build correctly.

Install shiboken2 target files using install(EXPORT)
to allow building PySide2 with an installed Shiboken2 package
(as opposed to one that is built as part of the super project).
Same with PySide2 targets for pyside2-tools subproject.

Make sure not to redefine uninstall targets if they are already
defined.

Add a --shorter-paths setup.py option, which would be used by
the Windows CI, to circumvent creating paths that are too long,
and thus avoiding build issues.

Output the build characteristics / classifiers into the generated
build_history/YYYY-MM-DD_AAAAAA/build_dir.txt file, so it can be
used by the test runner to properly filter out blacklisted
tests. This was necessary due to the shorter paths options.

Fix various issues regarding target includes and library
dependencies.

Remove certain duplicated cmake code (like limited api check and build
type checks) in PySide2, given that that information will now be
present in the exported shiboken2 config file.

Include a short README.cmake.md file that describes how to build
the super project.

References used
https://rix0r.nl/blog/2015/08/13/cmake-guide/
https://pabloariasal.github.io/2018/02/19/its-time-to-do-cmake-right/
https://gist.github.com/mbinna/c61dbb39bca0e4fb7d1f73b0d66a4fd1
https://cliutils.gitlab.io/modern-cmake/chapters/basics/functions.html
https://cmake.org/cmake/help/v3.0/manual/cmake-packages.7.html
https://github.com/ComicSansMS/libstratcom/blob/master/CMakeLists.txt

Abandoned approach using ExternalProject references:
https://cmake.org/cmake/help/latest/module/ExternalProject.html
https://stackoverflow.com/questions/44990964/how-to-perform-cmakefind-package-at-build-stage-only

Fixes: PYSIDE-919
Change-Id: Iaa15d20b279a04c5e16ce2795d03f912bc44a389
Reviewed-by: Cristian Maureira-Fredes <cristian.maureira-fredes@qt.io>

1 files changed, 17 insertions, 111 deletions

diff --git a/sources/pyside2/CMakeLists.txt b/sources/pyside2/CMakeLists.txt
index b2866a10f..1e6f017d7 100644
--- a/sources/pyside2/CMakeLists.txt
+++ b/sources/pyside2/CMakeLists.txt
@@ -8,20 +8,18 @@ cmake_policy(SET CMP0046 NEW)
 
 project(pysidebindings)
 
-set(CMAKE_MODULE_PATH ${CMAKE_SOURCE_DIR}/../cmake_helpers/
-                      ${CMAKE_SOURCE_DIR}/cmake/Macros/
+set(CMAKE_MODULE_PATH ${CMAKE_CURRENT_SOURCE_DIR}/../cmake_helpers/
+                      ${CMAKE_CURRENT_SOURCE_DIR}/cmake/Macros/
                       ${CMAKE_MODULE_PATH})
 include(helpers)
 
-option(USE_PYTHON_VERSION "Use specific python version to build pyside2." "")
-
 # Don't display "up-to-date / install" messages when installing, to reduce visual clutter.
 if (QUIET_BUILD)
     set(CMAKE_INSTALL_MESSAGE NEVER)
 endif()
 
 # Override message not to display info messages when doing a quiet build.
-if (QUIET_BUILD)
+if (QUIET_BUILD AND is_pyside2_superproject_build)
     function(message)
         list(GET ARGV 0 MessageType)
         if (MessageType STREQUAL FATAL_ERROR OR
@@ -34,15 +32,7 @@ if (QUIET_BUILD)
     endfunction()
 endif()
 
-if (USE_PYTHON_VERSION)
-    find_package(PythonInterp ${USE_PYTHON_VERSION} REQUIRED)
-    find_package(PythonLibs ${USE_PYTHON_VERSION} REQUIRED)
-else()
-    find_package(PythonInterp 2.7)
-    find_package(PythonLibs 2.7)
-endif()
-
-set(PYSIDE_VERSION_FILE_PATH "${CMAKE_SOURCE_DIR}/pyside_version.py")
+set(PYSIDE_VERSION_FILE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/pyside_version.py")
 set_property(DIRECTORY APPEND PROPERTY CMAKE_CONFIGURE_DEPENDS
   ${PYSIDE_VERSION_FILE_PATH}
 )
@@ -63,111 +53,28 @@ list(GET PYSIDE_VERSION_OUTPUT 3 BINDING_API_PRE_RELEASE_VERSION_TYPE)
 # the number of the pre release (alpha1, beta3, rc7, etc.)
 list(GET PYSIDE_VERSION_OUTPUT 4 BINDING_API_PRE_RELEASE_VERSION)
 
-macro(get_python_extension_suffix)
-  # Result of imp.get_suffixes() depends on the platform, but generally looks something like:
-  # [('.cpython-34m-x86_64-linux-gnu.so', 'rb', 3), ('.cpython-34m.so', 'rb', 3),
-  # ('.abi3.so', 'rb', 3), ('.so', 'rb', 3), ('.py', 'r', 1), ('.pyc', 'rb', 2)]
-  # We pick the first most detailed one, strip of the file extension part.
-
-  execute_process(
-    COMMAND ${PYTHON_EXECUTABLE} -c "if True:
-       import imp, re
-       first_suffix = imp.get_suffixes()[0][0]
-       res = re.search(r'^(.+)\\.', first_suffix)
-       if res:
-           first_suffix = res.group(1)
-       else:
-           first_suffix = ''
-       print(first_suffix)
-       "
-    OUTPUT_VARIABLE PYTHON_EXTENSION_SUFFIX
-    OUTPUT_STRIP_TRAILING_WHITESPACE)
-  message("PYTHON_EXTENSION_SUFFIX: " ${PYTHON_EXTENSION_SUFFIX})
-endmacro()
-
-
-if (NOT PYTHON_EXTENSION_SUFFIX)
-  get_python_extension_suffix()
-endif()
-
-# On Windows, PYTHON_LIBRARIES can be a list. Example:
-#    optimized;C:/Python36/libs/python36.lib;debug;C:/Python36/libs/python36_d.lib
-# On other platforms, this result is not used at all.
-execute_process(
-    COMMAND ${PYTHON_EXECUTABLE} -c "if True:
-        for lib in '${PYTHON_LIBRARIES}'.split(';'):
-            if '/' in lib:
-                prefix, py = lib.rsplit( '/', 1)
-                if py.startswith('python3'):
-                    print(prefix + '/python3.lib')
-                    break
-        "
-    OUTPUT_VARIABLE PYTHON_LIMITED_LIBRARIES
-    OUTPUT_STRIP_TRAILING_WHITESPACE)
-
 if (WIN32)
     set(PATH_SEP "\;")
 else()
     set(PATH_SEP ":")
 endif()
 
-option(FORCE_LIMITED_API "Enable the limited API." "yes")
+find_package(Shiboken2 2.0.0 REQUIRED)
 
-set(PYTHON_LIMITED_API 0)
-if(FORCE_LIMITED_API STREQUAL "yes")
-    # GREATER_EQUAL is available only from cmake 3.7 on. We mean python 3.5 .
-    if (${PYTHON_VERSION_MAJOR} EQUAL 3 AND ${PYTHON_VERSION_MINOR} GREATER 4)
-        add_definitions("-DPy_LIMITED_API=0x03050000")
-        set(PYTHON_LIMITED_API 1)
-    endif()
+if(NOT CMAKE_BUILD_TYPE)
+    set(CMAKE_BUILD_TYPE ${SHIBOKEN_BUILD_TYPE})
 endif()
+
 if (CMAKE_BUILD_TYPE STREQUAL "Release")
     add_definitions("-DNDEBUG")
 endif()
 
-if (PYTHON_LIMITED_API)
-    if (WIN32 AND NOT EXISTS "${PYTHON_LIMITED_LIBRARIES}")
-        message(FATAL_ERROR "The Limited API was enabled, but ${PYTHON_LIMITED_LIBRARIES} was not found!")
-    endif()
+if (SHIBOKEN_PYTHON_LIMITED_API)
     message(STATUS "******************************************************")
-    message(STATUS "** Limited API enabled ${PYTHON_LIMITED_LIBRARIES}")
+    message(STATUS "** PySide2 Limited API enabled.")
     message(STATUS "******************************************************")
 endif()
 
-if (NOT PYTHON_CONFIG_SUFFIX)
-  if (PYTHON_VERSION_MAJOR EQUAL 2)
-      set(PYTHON_CONFIG_SUFFIX "-python${PYTHON_VERSION_MAJOR}.${PYTHON_VERSION_MINOR}")
-      if (PYTHON_EXTENSION_SUFFIX)
-          set(PYTHON_CONFIG_SUFFIX "${PYTHON_CONFIG_SUFFIX}${PYTHON_EXTENSION_SUFFIX}")
-      endif()
-  elseif (PYTHON_VERSION_MAJOR EQUAL 3)
-      if (PYTHON_LIMITED_API)
-          if(WIN32)
-              set(PYTHON_EXTENSION_SUFFIX "")
-          else()
-              set(PYTHON_EXTENSION_SUFFIX ".abi3")
-          endif()
-      endif()
-      set(PYTHON_CONFIG_SUFFIX "${PYTHON_EXTENSION_SUFFIX}")
-  endif()
-endif()
-
-if (NOT PYTHON_SHARED_LIBRARY_SUFFIX)
-  set(PYTHON_SHARED_LIBRARY_SUFFIX "${PYTHON_CONFIG_SUFFIX}")
-
-  # Append a "v" to disambiguate the python version and the pyside version in the
-  # shared library file name.
-  if (APPLE AND PYTHON_VERSION_MAJOR EQUAL 2)
-      set(PYTHON_SHARED_LIBRARY_SUFFIX "${PYTHON_SHARED_LIBRARY_SUFFIX}v")
-  endif()
-endif()
-
-
-message(STATUS "PYTHON_EXTENSION_SUFFIX:      ${PYTHON_EXTENSION_SUFFIX}")
-message(STATUS "PYTHON_CONFIG_SUFFIX:         ${PYTHON_CONFIG_SUFFIX}")
-message(STATUS "PYTHON_SHARED_LIBRARY_SUFFIX: ${PYTHON_SHARED_LIBRARY_SUFFIX}")
-
-find_package(Shiboken2 2.0.0 REQUIRED)
 find_package(Qt5 5.12 REQUIRED COMPONENTS Core)
 add_definitions(${Qt5Core_DEFINITIONS})
 
@@ -188,7 +95,7 @@ endif()
 option(BUILD_TESTS "Build tests." TRUE)
 option(ENABLE_VERSION_SUFFIX "Used to use current version in suffix to generated files. This is used to allow multiples versions installed simultaneous." FALSE)
 set(LIB_SUFFIX "" CACHE STRING "Define suffix of directory name (32/64)" )
-set(LIB_INSTALL_DIR "${CMAKE_INSTALL_PREFIX}/lib${LIB_SUFFIX}" CACHE PATH "The subdirectory relative to the install prefix where libraries will be installed (default is /lib${LIB_SUFFIX})" FORCE)
+set(LIB_INSTALL_DIR "lib${LIB_SUFFIX}" CACHE PATH "The subdirectory relative to the install prefix where libraries will be installed (default is /lib${LIB_SUFFIX})" FORCE)
 if(CMAKE_HOST_APPLE)
     set(ALTERNATIVE_QT_INCLUDE_DIR "" CACHE PATH "Deprecated. CMake now finds the proper include dir itself.")
     set(OSX_USE_LIBCPP "OFF" CACHE BOOL "Explicitly link the libc++ standard library (useful for osx deployment targets lower than 10.9.")
@@ -231,7 +138,6 @@ else()
     set(CMAKE_CXX_FLAGS_DEBUG "-g")
     option(ENABLE_GCC_OPTIMIZATION "Enable specific GCC flags to optimization library size and performance. Only available on Release Mode" 0)
     if(ENABLE_GCC_OPTIMIZATION)
-        set(CMAKE_BUILD_TYPE Release)
         set(CMAKE_CXX_FLAGS_RELEASE "-DNDEBUG -Os -Wl,-O1")
         if(NOT CMAKE_HOST_APPLE)
             set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wl,--hash-style=gnu")
@@ -249,10 +155,6 @@ else()
 endif()
 message(STATUS "*** computed QT_INCLUDE_DIR as ${QT_INCLUDE_DIR}")
 
-if(NOT CMAKE_BUILD_TYPE)
-    set(CMAKE_BUILD_TYPE ${SHIBOKEN_BUILD_TYPE})
-endif()
-
 set(BINDING_NAME PySide2)
 
 set(BINDING_API_VERSION "${BINDING_API_MAJOR_VERSION}.${BINDING_API_MINOR_VERSION}.${BINDING_API_MICRO_VERSION}" CACHE STRING "PySide2 version" FORCE)
@@ -441,13 +343,17 @@ message(STATUS "Detected OS: ${AUTO_OS}")
 # Define supported Qt Version
 set(SUPPORTED_QT_VERSION "${QT_VERSION_MAJOR}.${QT_VERSION_MINOR}")
 
+
 # uninstall target
 configure_file("${CMAKE_CURRENT_SOURCE_DIR}/cmake_uninstall.cmake"
                "${CMAKE_CURRENT_BINARY_DIR}/cmake_uninstall.cmake"
                IMMEDIATE @ONLY)
-add_custom_target(uninstall "${CMAKE_COMMAND}"
-                  -P "${CMAKE_CURRENT_BINARY_DIR}/cmake_uninstall.cmake")
 
+# When opening super project, prevent redefinition of uninstall target.
+if (NOT TARGET uninstall)
+    add_custom_target(uninstall "${CMAKE_COMMAND}"
+                      -P "${CMAKE_CURRENT_BINARY_DIR}/cmake_uninstall.cmake")
+endif()
 
 if (NOT PYTHON_SITE_PACKAGES)
     execute_process(