build: fix scratch targets for file names containing dots in CMake < 3.14

scratch/CMakeLists.txt

@@ -30,7 +30,17 @@ function(create_scratch source_files)
   string(REPLACE "/" "_" scratch_dirname "${scratch_dirname}")
 
   # Get source name
-  get_filename_component(scratch_name ${scratch_src} NAME_WLE)
+  if(${CMAKE_VERSION} VERSION_GREATER_EQUAL "3.14.0")
+    get_filename_component(scratch_name ${scratch_src} NAME_WLE)
+  else()
+    get_filename_component(scratch_name ${scratch_src} NAME)
+    string(FIND "${scratch_name}" "." ext_position REVERSE)
+    if(${ext_position} EQUAL -1)
+      message(FATAL_ERROR "Source file has no extension: ${scratch_src}")
+    else()
+      string(SUBSTRING "${scratch_name}" 0 ${ext_position} scratch_name)
+    endif()
+  endif()
 
   set(target_prefix scratch_)
   if(scratch_dirname)

utils/tests/test-ns3.py

@@ -1254,6 +1254,25 @@ class NS3ConfigureTestCase(NS3BaseTestCase):
             else:
                 self.assertEqual(return_code, 1)
 
+        # Now test them in CMake 3.10
+        run_ns3("clean")
+        with DockerContainerManager(self, "ubuntu:18.04") as container:
+            container.execute("apt-get update")
+            container.execute("apt-get install -y python3 cmake g++-8 ninja-build")
+            try:
+                container.execute(
+                    "./ns3 configure --enable-modules=core,network,internet -- -DCMAKE_CXX_COMPILER=/usr/bin/g++-8")
+            except DockerException as e:
+                self.fail()
+            for path in test_files:
+                path = path.replace(".cc", "")
+                try:
+                    container.execute(f"./ns3 run {path}")
+                except DockerException as e:
+                    if "main" in path:
+                        self.fail()
+        run_ns3("clean")
+
         # Delete the test files and reconfigure to clean them up
         for path in test_files + backup_files:
             source_absolute_path = os.path.join(ns3_path, path)