Allow children in cnfvar templates

Some templates are not just lists of cnfvars, but contain elements that
required child cnfvars (e.g. the upcomping VPNCONN_WG_LOCAL_NET).
However, a CnfVar's "children" attribute cannot be set in the CnfVar
constructor, nor are there mechanisms to do that in other functions that
create CnfVars. Add functionality for this special case of creating
CnfVars from templates, where values are very-well controlled. Use dicts
to specify the children.

Also warn if naive users specify overwrite parameters including the "name"
like "VPNCONN_PROTO" (should only be "proto=...")

diff --git a/src/cnfvar/templates.py b/src/cnfvar/templates.py
index 5154a03..4c157fa 100644 (file)
--- a/src/cnfvar/templates.py
+++ b/src/cnfvar/templates.py
@@ -219,13 +219,25 @@ def template(name, value, instance=-1, defaults=None, **kwargs):
     :rtype: :py:class:`Cnf`
 
     All additional keyword arguments will be used to overwrite the defaults.
+    They cannot add new variables, not present in defaults.
     """
     log.info(f"Generating a template {name} cnfvar")
     cnf = Cnf(name, value=value, instance=instance)
     defaults = {} if defaults is None else defaults
-    cnf.add_children(*[(key, value) for key, value in defaults.items()])
+    for key, value in defaults.items():
+        if isinstance(value, dict):
+            sub_children = value.pop("children")
+            new_child = Cnf(name=key, **value)
+            new_child.add_children(*sub_children)
+            cnf.add_child(new_child)
+        else:
+            cnf.add_child(key, value)
+    prefix = name.lower() + "_"
     for key in kwargs.keys():
-        cnf.children.single_with_name(f"{name}_{key}").value = kwargs[key]
+        if key.lower().startswith(prefix):
+            log.warning(f"For overwriting template params, omit the leading name "
+                        f"(here: {name}_) from keys (here: {key})")
+        cnf.children.single_with_name(f"{prefix}{key}").value = kwargs[key]
     return cnf