build, bindings: check if cppyy is available at runtime and format cmake

bindings/python/ns__init__.py

@@ -33,7 +33,13 @@ def load_modules():
     ns3_output_directory = values["out_dir"]
     libraries = {x.split(".")[0]: x for x in os.listdir(os.path.join(ns3_output_directory, "lib"))}
 
-    import cppyy
+    # Try to import Cppyy and warn the user in case it is not found
+    try:
+        import cppyy
+    except ModuleNotFoundError:
+        print("Cppyy is required by the ns-3 python bindings.")
+        print("You can install it with the following command: pip install cppyy")
+        exit(-1)
 
     # Enable full logs for debugging
     # cppyy.set_debug(True)

build-support/macros-and-definitions.cmake

@@ -756,12 +756,14 @@ macro(process_options)
         )
       else()
         set(ENABLE_PYTHON_BINDINGS ON)
-
-        set(destination_dir ${CMAKE_OUTPUT_DIRECTORY}/bindings/python/ns)
-        configure_file(
-          bindings/python/ns__init__.py ${destination_dir}/__init__.py COPYONLY
-        )
       endif()
+
+      # Copy the bindings file if we have python, which will prevent python
+      # scripts from failing due to the missing ns package
+      set(destination_dir ${CMAKE_OUTPUT_DIRECTORY}/bindings/python/ns)
+      configure_file(
+        bindings/python/ns__init__.py ${destination_dir}/__init__.py COPYONLY
+      )
     endif()
   endif()
 

examples/CMakeLists.txt

@@ -13,7 +13,6 @@ if(${ENABLE_EXAMPLES})
         CACHE INTERNAL "list of example folders"
     )
   endforeach()
-  scan_python_examples(${CMAKE_CURRENT_SOURCE_DIR})
 endif()
 
 scan_python_examples(${CMAKE_CURRENT_SOURCE_DIR})

examples/realtime/CMakeLists.txt

@@ -1,7 +1,7 @@
 build_example(
-NAME realtime-udp-echo
-SOURCE_FILES realtime-udp-echo.cc
-LIBRARIES_TO_LINK
+  NAME realtime-udp-echo
+  SOURCE_FILES realtime-udp-echo.cc
+  LIBRARIES_TO_LINK
     ${libcsma}
     ${libinternet}
     ${libapplications}

examples/wireless/CMakeLists.txt

@@ -291,4 +291,3 @@ build_example(
   SOURCE_FILES wifi-ofdm-eht-validation.cc
   LIBRARIES_TO_LINK ${libwifi}
 )
-

src/tap-bridge/CMakeLists.txt

@@ -1,4 +1,6 @@
-if(NOT ${ENABLE_EMU})
+if(NOT
+   ${ENABLE_EMU}
+)
   message(
     ${HIGHLIGHTED_STATUS}
     "tap-bridge requires emulation feature"