cmake: add requires to add_subdirectory wrapper

Author: AshFungor

CMakeLists.txt

@@ -32,28 +32,6 @@ option(WITH_TRANSFUSION "Build Artery with transfusion feature" OFF)
 option(WITH_SCENARIOS "Build Artery with scenarios" ON)
 option(VSCODE_LAUNCH_INTEGRATION "Generate VS Code configuration for debugging Artery (requires debug build)" OFF)
 
-#################################
-# Resolving conflicting options #
-#################################
-
-if(NOT WITH_INET)
-    # SimuLTE extends INET network (see src/artery/lte/World.ned)
-    if(WITH_SIMULTE)
-        message(ERROR "SimuLTE requires INET framework integration (WITH_INET must be set to ON)")
-    endif()
-
-    # Components below use INET classes
-    if(WITH_OTS)
-        message(ERROR "OpenTrafficSim requires INET framework integration (WITH_INET must be set to ON)")
-    endif()
-    if(WITH_TESTBED)
-        message(ERROR "Testbed requires INET framework integration (WITH_INET must be set to ON)")
-    endif()
-    if(WITH_ENVMOD)
-        message(ERROR "Environment model requires INET framework integration (WITH_INET must be set to ON)")
-    endif()
-endif()
-
 ##############################
 # Artery build configuration #
 ##############################
@@ -128,7 +106,7 @@ endmacro()
 add_subdirectory(src/traci)
 add_subdirectory(src/artery)
 
-add_artery_subdirectory(src/ots DEPENDENCIES ZEROMQ SWITCH WITH_OTS)
+add_artery_subdirectory(src/ots REQUIRES INET DEPENDENCIES ZEROMQ SWITCH WITH_OTS)
 
 # scenarios directory is part of repository but omitted for Docker build context
 if(WITH_SCENARIOS)

cmake/AddArterySubdirectory.cmake

@@ -1,6 +1,15 @@
 function(add_artery_subdirectory directory)
+    # include target subdirectory with certain artery
+    # extension (feature), if the following conditions match:
+    # 1) variable with id matching SWITCH is set to true (feature turned on)
+    # 2) packages that are listed in DEPENDENCIES are found
+    # 3) targets that are listed in REQUIRES are declared (used for extern modules)
+
+    # If condition 1) is not met, then subdirectory is not added and
+    # debug message is issued. If either 2) or 3) fails, then this function raises error.
+
     set(one_value_args SWITCH)
-    set(multi_value_args DEPENDENCIES)
+    set(multi_value_args DEPENDENCIES;REQUIRES)
     cmake_parse_arguments(args "" "${one_value_args}" "${multi_value_args}" ${ARGN})
 
     if(args_UNPARSED_ARGUMENTS)
@@ -17,7 +26,16 @@ function(add_artery_subdirectory directory)
             if(NOT DEFINED ${_dep_var} OR NOT ${_dep_var})
                 message(
                     FATAL_ERROR
-                    "add_artery_subdirectory: required dependency '${dependency}' for '${directory}' not found: variable '${_dep_var}' is not defined"
+                    "add_artery_subdirectory: dependency '${dependency}' for '${directory}' was not found: variable '${_dep_var}' is not defined"
+                )
+            endif()
+        endforeach()
+
+        foreach(required_target IN LISTS args_REQUIRES)
+            if(NOT TARGET ${required_target})
+                message(
+                    FATAL_ERROR
+                    "add_artery_subdirectory: required target '${required_target}' for '${directory}' was not found"
                 )
             endif()
         endforeach()

extern/CMakeLists.txt

@@ -72,9 +72,15 @@ if(WITH_INET)
 endif()
 
 if(WITH_SIMULTE)
+    message(STATUS "Enable SimuLTE integration")
+    if(NOT TARGET INET)
+        message(FATAL_ERROR "SimuLTE requires INET")
+    endif()
+
     check_git_submodule(PATH simulte REQUIRED_FILES src/package.ned)
     find_path(SimuLTE_DIR NAMES src/package.ned PATHS simulte DOC "SimuLTE root directory")
     mark_as_advanced(SimuLTE_DIR)
+
     add_opp_target(TARGET lte ROOT_DIR ${SimuLTE_DIR})
     target_link_libraries(lte PUBLIC INET)
 else()

src/artery/CMakeLists.txt

@@ -43,16 +43,15 @@ add_artery_subdirectory(inet SWITCH WITH_INET)
 add_artery_subdirectory(storyboard SWITCH WITH_STORYBOARD)
 
 add_artery_subdirectory(transfusion DEPENDENCIES Protobuf SWITCH WITH_TRANSFUSION)
-add_artery_subdirectory(testbed DEPENDENCIES SEA_V2X Protobuf SWITCH WITH_TESTBED)
+add_artery_subdirectory(testbed REQUIRES INET DEPENDENCIES SEA_V2X Protobuf SWITCH WITH_TESTBED)
 
 if(TARGET lte)
     # SimuLTE is a non-integral feature: add it to "artery" but not "core"
-    message(STATUS "Enable SimuLTE integration")
     target_link_libraries(artery INTERFACE lte)
 endif()
 
+add_artery_subdirectory(envmod REQUIRES INET SWITCH WITH_ENVMOD)
 if(WITH_ENVMOD)
-    add_subdirectory(envmod)
     set_property(SOURCE application/VehicleMiddleware.cc APPEND PROPERTY COMPILE_DEFINITIONS "WITH_ENVMOD")
 endif()