fix: handle nested arguments in the argument parser

Mostly coming from libraries such as simple-parsing, who nest the
values, but this can also be done manually, so might as well account for
it.
Also this makes sure the values are serialisable, as JSON is very
restrictive and Python doesn't allow to handle it gracefully (as in
having the possibility to define how an object is serialised).

py/lavd/log.py

@@ -1070,18 +1070,23 @@ def assign_args_to_options(
 ) -> Dict[str, Union[List, Dict]]:
     pos = []
     opts = {}
-    for key, value in vars(args).items():
+    for key, o in options.items():
         # None values are not saved, they just cause trouble because they are null and
         # undefined, and they should rather not be present than being null.
+        if o is None:
+            continue
+        value = get_recursive_option(args, key)
         if value is None:
             continue
-        if key in positionals:
-            pos.append(value)
-        else:
-            o = options.get(key)
-            if o is not None:
-                name = o.get("name") or key
-                opts[name] = value
+        name = o.get("name") or key
+        opts[name] = ensure_serialisable(value)
+    for key, o in positionals.items():
+        if o is None:
+            continue
+        value = get_recursive_option(args, key)
+        if value is None:
+            continue
+        pos.append(ensure_serialisable(value))
     out: Dict[str, Union[List, Dict]] = {}
     if len(pos) > 0:
         out["positional"] = pos
@@ -1090,6 +1095,33 @@ def assign_args_to_options(
     return out
 
 
+# Convert everything that is not serialisable by the JSON module to strings to make them
+# serialisable.
+def ensure_serialisable(value: Any) -> Any:
+    if isinstance(value, dict):
+        return {k: ensure_serialisable(v) for k, v in value.items()}
+    elif isinstance(value, (list, tuple)):
+        return [ensure_serialisable(v) for v in value]
+    elif not isinstance(value, (str, int, float, bool)):
+        return str(value)
+    else:
+        return value
+
+
+def get_recursive_option(options: Any, key: str) -> Optional[Any]:
+    curr = options
+    for k in key.split("."):
+        if not isinstance(options, dict):
+            try:
+                curr = vars(curr)
+            except TypeError:
+                raise KeyError(f"Could not get key={key} from {curr}")
+        curr = curr.get(k)
+        if curr is None:
+            return None
+    return curr
+
+
 def pad_table_row(row: List[str], widths: List[int], value: str = " ") -> List[str]:
     return [
         "{field:{pad}<{width}}".format(field=field, pad=value, width=width)