Fix: no underscores in topology.name generated from input directory (#2497)

Underscores in topology.name are used by clab to generate hostnames,
and some Linux distros don't grasp that a clumsy person might have
underscores in hostnames.

This fix ensures there are no weird characters in topology.name that
is generated from the input directory (and 'default' is used when
nothing is left after the cleanup). We don't check what the user
specifies in the 'name' argument (they should know better ;)

Fixes #2424

Author: ipspace

netsim/augment/topology.py

@@ -15,12 +15,33 @@
 from ..data.validate import validate_attributes,get_object_attributes
 from ..data.types import must_be_list,must_be_string,must_be_dict
 
+"""
+Generate topology name from the lab topology file location:
+
+* Take the first entry in the 'input' list (the original topology name)
+* Expand it to full path, then take the rightmost directory name from the path
+* Make an ID out of the directory name (removing everything but ASCII letters
+  and numbers)
+* Remove underscores from ID (see #2424)
+* If nothing is left, assume the topology name is 'default'
+"""
+def name_from_path(topology: Box) -> str:
+  topo_name = os.path.basename(os.path.dirname(os.path.realpath(topology['input'][0])))
+  topo_name = strings.make_id(topo_name).replace('_','')
+  if not topo_name:
+    topo_name = 'default'
+  return topo_name
+
+"""
+Basic topology sanity check:
+
+* It should have a name (set one from lab topology directory if needed) that
+  should be a string
+* The 'module' attribute (if present) must be a list
+"""
 def topology_sanity_check(topology: Box) -> None:
   if not 'name' in topology:
-    topo_name = os.path.basename(os.path.dirname(os.path.realpath(topology['input'][0])))[:12]
-    for bad_char in (' ','.'):
-      topo_name = topo_name.replace(bad_char,'_')
-    topology.name = strings.make_id(topo_name)
+    topology.name = name_from_path(topology)[:12]
 
   if 'module' in topology:
     must_be_list(topology,'module','')
@@ -29,6 +50,9 @@ def topology_sanity_check(topology: Box) -> None:
   if must_be_string(topology,'name','',module='topology'):
     topology.defaults.name = topology.name
 
+"""
+Check required topology elements (currently: nodes)
+"""
 def check_required_elements(topology: Box) -> None:
   invalid_topo = False
   for rq in ['nodes']: