FindEnvModules: Provide a CMake interface to environment modules

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+# Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+# file Copyright.txt or https://cmake.org/licensing for details.
+
+#[=======================================================================[.rst:
+FindEnvModules
+--------------
+
+Locate an environment module implementation and make commands available to
+CMake scripts to use them.  This is compatible with both Lua-based Lmod
+and TCL-based EnvironmentModules.
+
+This module is intended for the use case of setting up the compiler and library
+environment within a :ref:`CTest Script <CTest Script>` (``ctest -S``).  It can
+also be used in a :ref:`CMake Script <Script Processing Mode>` (``cmake -P``).
+
+.. note::
+
+  The loaded environment will not survive past the end of the calling process.
+  Do not use this module in project code (``CMakeLists.txt`` files) to load
+  a compiler environment; it will not be available during the build.  Instead
+  load the environment manually before running CMake or using the generated
+  build system.
+
+Example Usage
+^^^^^^^^^^^^^
+
+.. code-block:: cmake
+
+  set(CTEST_BUILD_NAME "CrayLinux-CrayPE-Cray-dynamic")
+  set(CTEST_BUILD_CONFIGURATION Release)
+  set(CTEST_BUILD_FLAGS "-k -j8")
+  set(CTEST_CMAKE_GENERATOR "Unix Makefiles")
+
+  ...
+
+  find_package(EnvModules REQUIRED)
+
+  env_module(purge)
+  env_module(load modules)
+  env_module(load craype)
+  env_module(load PrgEnv-cray)
+  env_module(load craype-knl)
+  env_module(load cray-mpich)
+  env_module(load cray-libsci)
+
+  set(ENV{CRAYPE_LINK_TYPE} dynamic)
+
+  ...
+
+Result Variables
+^^^^^^^^^^^^^^^^
+
+This module will set the following variables in your project:
+
+``EnvModules_FOUND``
+  Found the a compatible environment modules framework
+
+Cache Variables
+^^^^^^^^^^^^^^^
+
+The following cache variable will be set:
+
+``EnvModules_COMMAND``
+  The low level module command to use.  Currently supported are
+  implementations are the Lua based Lmod and TCL based EnvironmentModules.
+
+Environment Variables
+^^^^^^^^^^^^^^^^^^^^^
+
+``ENV{MODULESHOME}``
+  Usually set by the module environment implementation, used as a hint to
+  locate the module command to execute.
+
+Provided Functions
+^^^^^^^^^^^^^^^^^^
+
+This defines the following cmake functions for interacting with environment
+modules:
+
+.. command:: env_module
+
+  Execute an aribitrary module command:
+
+  .. code-block:: cmake
+
+    env_module(cmd arg1 ... argN)
+    env_module(
+      COMMAND cmd arg1 ... argN
+      [OUTPUT_VARIABLE <out-var>]
+      [RESULT_VARIABLE <ret-var>]
+    )
+
+  The options are:
+
+  ``cmd arg1 ... argN``
+    The module sub-command and arguments to execute as if they were
+    passed directly to the module command in your shell environment.
+
+  ``OUTPUT_VARIABLE <out-var>``
+    The standard output from executing the module command.
+
+  ``RESULT_VARIABLE <ret-var>``
+    The return code from executing the module command.
+
+.. command:: env_module_swap
+
+  Swap one module for another:
+
+  .. code-block:: cmake
+
+    env_module_swap(out_mod in_mod
+      [OUTPUT_VARIABLE <out-var>]
+      [RESULT_VARIABLE <ret-var>]
+    )
+
+  This is functionally equivalent to the ``module swap out_mod in_mod`` shell
+  command.  The options are:
+
+  ``OUTPUT_VARIABLE <out-var>``
+    The standard output from executing the module command.
+
+  ``RESULT_VARIABLE <ret-var>``
+    The return code from executing the module command.
+
+.. command:: env_module_list
+
+  Retrieve the list of currently loaded modules:
+
+  .. code-block:: cmake
+
+    env_module_list(<out-var>)
+
+  This is functionally equivalent to the ``module list`` shell command.
+  The result is stored in ``<out-var>`` as a properly formatted CMake
+  :ref:`semicolon-separated list <CMake Language Lists>` variable.
+
+.. command:: env_module_avail
+
+  Retrieve the list of available modules:
+
+  .. code-block:: cmake
+
+    env_module_avail([<mod-prefix>] <out-var>)
+
+  This is functionally equivalent to the ``module avail <mod-prefix>`` shell
+  command.  The result is stored in ``<out-var>`` as a properly formatted
+  CMake :ref:`semicolon-separated list <CMake Language Lists>` variable.
+
+#]=======================================================================]
+
+function(env_module)
+  if(NOT EnvModules_COMMAND)
+    message(FATAL_ERROR "Failed to process module command.  EnvModules_COMMAND not found")
+    return()
+  endif()
+
+  set(options)
+  set(oneValueArgs OUTPUT_VARIABLE RESULT_VARIABLE)
+  set(multiValueArgs COMMAND)
+  cmake_parse_arguments(MOD_ARGS
+    "${options}" "${oneValueArgs}" "${multiValueArgs}" ${ARGV}
+  )
+  if(NOT MOD_ARGS_COMMAND)
+    # If no explicit command argument was given, then treat the calling syntax
+    # as: module(cmd args...)
+    set(exec_cmd ${ARGV})
+  else()
+    set(exec_cmd ${MOD_ARGS_COMMAND})
+  endif()
+
+  if(MOD_ARGS_OUTPUT_VARIABLE)
+    set(err_var_args ERROR_VARIABLE err_var)
+   endif()
+
+  execute_process(
+    COMMAND mktemp -t module.cmake.XXXXXXXXXXXX
+    OUTPUT_VARIABLE tempfile_name
+  )
+  string(STRIP "${tempfile_name}" tempfile_name)
+
+  # If the $MODULESHOME/init/cmake file exists then assume that the CMake
+  # "shell" functionality exits
+  if(EXISTS "$ENV{MODULESHOME}/init/cmake")
+    execute_process(
+      COMMAND ${EnvModules_COMMAND} cmake ${exec_cmd}
+      OUTPUT_FILE ${tempfile_name}
+      ${err_var_args}
+      RESULT_VARIABLE ret_var
+    )
+
+  else() # fallback to the sh shell and manually convert to CMake
+    execute_process(
+      COMMAND ${EnvModules_COMMAND} sh ${exec_cmd}
+      OUTPUT_VARIABLE out_var
+      ${err_var_args}
+      RESULT_VARIABLE ret_var
+    )
+  endif()
+
+  # If we executed successfully then process and cleanup the temp file
+  if(ret_var EQUAL 0)
+    # No CMake shell so we need to process the sh output into CMake code
+    if(NOT EXISTS "$ENV{MODULESHOME}/init/cmake")
+      file(WRITE ${tempfile_name} "")
+      string(REPLACE "\n" ";" out_var "${out_var}")
+      foreach(sh_cmd IN LISTS out_var)
+        if(sh_cmd MATCHES "^ *unset *([^ ]*)")
+          set(cmake_cmd "unset(ENV{${CMAKE_MATCH_1}})")
+        elseif(sh_cmd MATCHES "^ *export *([^ ]*)")
+          set(cmake_cmd "set(ENV{${CMAKE_MATCH_1}} \"\${${CMAKE_MATCH_1}}\")")
+        elseif(sh_cmd MATCHES " *([^ =]*) *= *(.*)")
+          set(var_name "${CMAKE_MATCH_1}")
+          set(var_value "${CMAKE_MATCH_2}")
+          if(var_value MATCHES "^\"(.*[^\\])\"")
+            # If it's in quotes, take the value as is
+            set(var_value "${CMAKE_MATCH_1}")
+          else()
+            # Otherwise, strip trailing spaces
+            string(REGEX REPLACE "([^\\])? +$" "\\1" var_value "${var_value}")
+          endif()
+          string(REPLACE "\\ " " " var_value "${var_value}")
+          set(cmake_cmd "set(${var_name} \"${var_value}\")")
+        else()
+          continue()
+        endif()
+        file(APPEND ${tempfile_name} "${cmake_cmd}\n")
+      endforeach()
+    endif()
+
+    # Process the change in environment variables
+    include(${tempfile_name})
+    file(REMOVE ${tempfile_name})
+  endif()
+
+  # Push the output back out to the calling scope
+  if(MOD_ARGS_OUTPUT_VARIABLE)
+    set(${MOD_ARGS_OUTPUT_VARIABLE} "${err_var}" PARENT_SCOPE)
+  endif()
+  if(MOD_ARGS_RESULT_VARIABLE)
+    set(${MOD_ARGS_RESULT_VARIABLE} ${ret_var} PARENT_SCOPE)
+  endif()
+endfunction(env_module)
+
+#------------------------------------------------------------------------------
+function(env_module_swap out_mod in_mod)
+  set(options)
+  set(oneValueArgs OUTPUT_VARIABLE RESULT_VARIABLE)
+  set(multiValueArgs)
+
+  cmake_parse_arguments(MOD_ARGS
+    "${options}" "${oneValueArgs}" "${multiValueArgs}" ${ARGV}
+  )
+
+  env_module(COMMAND -t swap ${out_mod} ${in_mod}
+    OUTPUT_VARIABLE tmp_out
+    RETURN_VARIABLE tmp_ret
+  )
+
+  if(MOD_ARGS_OUTPUT_VARIABLE)
+    set(${MOD_ARGS_OUTPUT_VARIABLE} "${err_var}" PARENT_SCOPE)
+  endif()
+  if(MOD_ARGS_RESULT_VARIABLE)
+    set(${MOD_ARGS_RESULT_VARIABLE} ${tmp_ret} PARENT_SCOPE)
+  endif()
+endfunction()
+
+#------------------------------------------------------------------------------
+function(env_module_list out_var)
+  cmake_policy(SET CMP0007 NEW)
+  env_module(COMMAND -t list OUTPUT_VARIABLE tmp_out)
+
+  # Convert output into a CMake list
+  string(REPLACE "\n" ";" ${out_var} "${tmp_out}")
+
+  # Remove title headers and empty entries
+  list(REMOVE_ITEM ${out_var} "No modules loaded")
+  if(${out_var})
+    list(FILTER ${out_var} EXCLUDE REGEX "^(.*:)?$")
+  endif()
+  list(FILTER ${out_var} EXCLUDE REGEX "^(.*:)?$")
+
+  set(${out_var} ${${out_var}} PARENT_SCOPE)
+endfunction()
+
+#------------------------------------------------------------------------------
+function(env_module_avail)
+  cmake_policy(SET CMP0007 NEW)
+
+  if(ARGC EQUAL 1)
+    set(mod_prefix)
+    set(out_var ${ARGV0})
+  elseif(ARGC EQUAL 2)
+    set(mod_prefix ${ARGV0})
+    set(out_var ${ARGV1})
+  else()
+    message(FATAL_ERROR "Usage: env_module_avail([mod_prefix] out_var)")
+  endif()
+  env_module(COMMAND -t avail ${mod_prefix} OUTPUT_VARIABLE tmp_out)
+
+  # Convert output into a CMake list
+  string(REPLACE "\n" ";" tmp_out "${tmp_out}")
+
+  set(${out_var})
+  foreach(MOD IN LISTS tmp_out)
+    # Remove directory entries and empty values
+    if(MOD MATCHES "^(.*:)?$")
+      continue()
+    endif()
+
+    # Convert default modules
+    if(MOD MATCHES "^(.*)/$" ) # "foo/"
+      list(APPEND ${out_var} ${CMAKE_MATCH_1})
+    elseif(MOD MATCHES "^((.*)/.*)\\(default\\)$") # "foo/1.2.3(default)"
+      list(APPEND ${out_var} ${CMAKE_MATCH_2})
+      list(APPEND ${out_var} ${CMAKE_MATCH_1})
+    else()
+      list(APPEND ${out_var} ${MOD})
+    endif()
+  endforeach()
+
+  set(${out_var} ${${out_var}} PARENT_SCOPE)
+endfunction()
+
+#------------------------------------------------------------------------------
+# Make sure we know where the underlying module command is
+find_program(EnvModules_COMMAND
+  NAMES lmod modulecmd
+  HINTS ENV MODULESHOME
+  PATH_SUFFIXES libexec
+)
+
+include(${CMAKE_CURRENT_LIST_DIR}/FindPackageHandleStandardArgs.cmake)
+find_package_handle_standard_args(EnvModules DEFAULT_MSG EnvModules_COMMAND)