Add option to install concrete python requirements

Depending on the situation, fulfilling the concrete package requirements (from requirements.txt) is required. Usually, abstract dependencies (from setup.py) are sufficient. This MR simply makes concrete dependency installation optional.

Additionally, this MR fixes a little bug in CMake when installing abstract dependencies.

cmake/modules/DunePythonInstallPackage.cmake

@@ -15,6 +15,12 @@
 #       Variable where to store the result of the dependency configuration.
 #       A non-zero result stands for a failure on the configuration of the dependencies.
 #
+#    .. cmake_param:: INSTALL_CONCRETE_DEPENDENCIES
+#       :option:
+#
+#       This option forces the package dependencies to be installed with concrete dependencies
+#       listed on the requirements.txt file
+#
 #     This function installs the dependencies of a python package at configure time.
 #     The dependencies are extracted from the :setup.py: and :requiements.txt: file
 #     A failure on the installation of the dependencies does will no trigger a
@@ -83,6 +89,11 @@
 #
 #       Parameters to add to any :code:`pip install` call (appended).
 #
+#    .. cmake_param:: INSTALL_CONCRETE_DEPENDENCIES
+#       :option:
+#
+#       See :dune_python_configure_dependencies:
+#
 #    This function installs the python package located at the given path:
 #
 #    * installs it to the location specified with :ref:`DUNE_PYTHON_INSTALL_LOCATION` during
@@ -148,7 +159,7 @@ include_guard(GLOBAL)
 function(dune_python_configure_dependencies)
   # Parse Arguments
   set(OPTION)
-  set(SINGLE PATH RESULT)
+  set(SINGLE PATH RESULT DEPENDECY_SOURCE)
   cmake_parse_arguments(PYCONFDEPS "${OPTION}" "${SINGLE}" "${MULTI}" ${ARGN})
   if(PYCONFDEPS_UNPARSED_ARGUMENTS)
     message(WARNING "Unparsed arguments in dune_python_configure_dependencies: This often indicates typos!")
@@ -173,9 +184,9 @@ function(dune_python_configure_dependencies)
     set(WHEEL_OPTION "--find-links=file://${DUNE_PYTHON_WHEELHOUSE}")
   endif()
 
-
-  # if requirements file exists, install them directly
-  if(EXISTS "${PYCONFDEPS_PATH}/requirements.txt")
+  if(PYCONFDEPS_INSTALL_CONCRETE_DEPENDENCIES)
+    # if requirements file exists, install them directly
+    message(STATUS "Installing python package concrete requirements at ${PYPKGCONF_PATH}/requirements.txt")
     # Install requirements (e.g. not dune packages) once at configure stage
     dune_execute_process(COMMAND ${DUNE_PYTHON_VIRTUALENV_EXECUTABLE} -m pip install
                                   "${WHEEL_OPTION}"
@@ -200,10 +211,11 @@ function(dune_python_configure_dependencies)
   endif()
 
   # generate egg_info requirement file from setup.py
-  string(MD5 PACKAGE_HASH "${PYINST_PATH}")
-  file(MAKE_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/${PACKAGE_HASH}")
+  string(MD5 PACKAGE_HASH "${PYCONFDEPS_PATH}")
+  set(EGG_INFO_PATH "${CMAKE_CURRENT_BINARY_DIR}/${PACKAGE_HASH}")
+  file(MAKE_DIRECTORY "${EGG_INFO_PATH}")
   dune_execute_process(COMMAND ${DUNE_PYTHON_VIRTUALENV_EXECUTABLE} setup.py
-                        egg_info --egg-base "${CMAKE_CURRENT_BINARY_DIR}/${PACKAGE_HASH}"
+                        egg_info --egg-base "${EGG_INFO_PATH}"
                         WORKING_DIRECTORY "${PYCONFDEPS_PATH}"
                         RESULT_VARIABLE REQUIREMENTS_FAILED
                         ERROR_VARIABLE DEPENDENCIES_ERROR
@@ -219,12 +231,12 @@ function(dune_python_configure_dependencies)
   endif()
 
   # find the generated egg-info folder and install each dependency listed on the requires.txt file
-  file(GLOB EGG_INFO_PATH LIST_DIRECTORIES TRUE "${CMAKE_CURRENT_BINARY_DIR}/${PACKAGE_HASH}/*.egg-info")
+  file(GLOB EGG_INFO_PATH LIST_DIRECTORIES TRUE "${EGG_INFO_PATH}/*.egg-info")
   if(EXISTS "${EGG_INFO_PATH}/requires.txt")
     file(READ "${EGG_INFO_PATH}/requires.txt" PACKAGE_REQUIREMENTS)
     string(REPLACE "\n" ";" PACKAGE_REQUIREMENTS ${PACKAGE_REQUIREMENTS})
     string(REPLACE ";" " " PACKAGE_REQUIREMENTS_STR "${PACKAGE_REQUIREMENTS}")
-    message(STATUS "Installing python requirements: " ${PACKAGE_REQUIREMENTS_STR})
+    message(STATUS "Installing python package abstract requirements: " ${PACKAGE_REQUIREMENTS_STR})
     foreach(requirement IN LISTS PACKAGE_REQUIREMENTS)
       if("${requirement}" STREQUAL "")
         continue()
@@ -232,6 +244,7 @@ function(dune_python_configure_dependencies)
       if (requirement MATCHES "^\\[")
         # sections (e.g. "[<section>]") in setuptools define the start of optional requirements
         set(OPTIONAL_PACKAGE ON)
+        set(PYCONFDEPS_OPT "(optional) ")
         continue()
       endif()
       # Install requirements (e.g. not dune packages) once at configure stage
@@ -243,7 +256,7 @@ function(dune_python_configure_dependencies)
                                     "${requirement}"
                           RESULT_VARIABLE INSTALL_FAILED
                           ERROR_VARIABLE DEPENDENCIES_ERROR
-                          WARNING_MESSAGE "python package requirement '${requirement}' could not be installed - possibly connection to the python package index failed\n${DEPENDENCIES_ERROR}"
+                          WARNING_MESSAGE "Python ${PYCONFDEPS_OPT}package requirement '${requirement}' could not be installed - possibly connection to the python package index failed\n${DEPENDENCIES_ERROR}"
                           )
       if(NOT OPTIONAL_PACKAGE)
         if(INSTALL_FAILED)
@@ -419,7 +432,7 @@ endfunction()
 
 function(dune_python_configure_package)
   # Parse Arguments
-  set(SINGLE PATH RESULT INSTALL_TARGET)
+  set(SINGLE PATH RESULT INSTALL_TARGET INSTALL_CONCRETE_DEPENDENCIES)
   set(MULTI ADDITIONAL_PIP_PARAMS)
   cmake_parse_arguments(PYPKGCONF "${OPTION}" "${SINGLE}" "${MULTI}" ${ARGN})
   if(PYPKGCONF_UNPARSED_ARGUMENTS)
@@ -432,7 +445,9 @@ function(dune_python_configure_package)
 
   dune_python_configure_dependencies(
        PATH ${PYPKGCONF_PATH}
-       RESULT PYTHON_DEPENDENCIES_FAILED)
+       RESULT PYTHON_DEPENDENCIES_FAILED
+       ${PYPKGCONF_INSTALL_CONCRETE_DEPENDENCIES}
+  )
 
   if (PYTHON_DEPENDENCIES_FAILED)
     set(${PYPKGCONF_RESULT} ${PYTHON_DEPENDENCIES_FAILED} PARENT_SCOPE)
@@ -545,7 +560,7 @@ function(dune_python_configure_bindings)
   set(MULTI ADDITIONAL_PIP_PARAMS CMAKE_METADATA_FLAGS)
   cmake_parse_arguments(PYCONFBIND "${OPTION}" "${SINGLE}" "${MULTI}" ${ARGN})
   if(PYCONFBIND_UNPARSED_ARGUMENTS)
-    message(WARNING "Unparsed arguments in dune_python_install_package: This often indicates typos!")
+    message(WARNING "Unparsed arguments in dune_python_configure_bindings: This often indicates typos!")
   endif()
 
   # set the new package name