From 209829ffe34cb376f715bf4ef65e7307ea911931 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maximilian=20Ke=C3=9Fler?= <git@maximilian-kessler.de>
Date: Wed, 9 Feb 2022 12:38:40 +0100
Subject: [PATCH] better cleaning functions / add documentation

---
 PyTeX/format/config.py | 44 ++++++++++++++++++++++++++++++++++++------
 1 file changed, 38 insertions(+), 6 deletions(-)

diff --git a/PyTeX/format/config.py b/PyTeX/format/config.py
index af09e86..5965dd5 100644
--- a/PyTeX/format/config.py
+++ b/PyTeX/format/config.py
@@ -1,26 +1,58 @@
 from __future__ import annotations
 import json
 from pathlib import Path
-from typing import Dict, Optional, Union
+from typing import Dict, Optional, Union, List
 
 import yaml
 
+def clean_list(list_: List) -> Optional[List]:
+    """
+    Recursively removes all entries from list that are None,
+    empty dictionaries or empty lists.
+    Dicts ore lists that are None after cleaning will also be removed
+
+    Typically applied before dumping data to JSON where None values are default
+    and will be restored on read-in 'automatically'
+
+    :return:
+    :param list_: Any list
+    :return:
+    """
+    ret = []
+    for elem in list_:
+        if type(elem) == list:
+            ret.append(clean_list(elem))
+        elif type(elem) == dict:
+            ret.append(clean_dict(elem))
+        elif elem is not None:
+            ret.append(elem)
+    return ret if ret != [] else None
 
 def clean_dict(dictionary: Dict) -> Optional[Dict]:
+    """
+    Recursively removes all entries from dictionary that are None,
+    empty dictionaries or empty lists.
+    Keys whose value is a dict / list that only contains non-valued keys will
+    then also be removed.
+
+    Typically applied before dumping data to JSON where None values are default
+    and will be restored on read-in 'automatically'
+
+    :param dictionary: Any dictionary
+    :return:
+    """
     aux: Dict = {
               k: clean_dict(v) for k, v in dictionary.items() if type(v) == dict
     } | {
-        k: [
-            clean_dict(elem) if type(elem) == dict else elem
-            for elem in elems
-        ] for k, elems in dictionary.items() if type(elems) == list
+        k: clean_list(v)
+        for k, v in dictionary.items() if type(v) == list
     } | {
         k: v for k, v in dictionary.items() if type(v) != dict and type(v) != list
     }
     aux2: Dict = {
         k: v for k, v in aux.items() if v is not None
     }
-    return aux2 if aux2 != {} else None
+    return aux2 if aux2 != {} and aux2 != [] else None
 
 
 class Config: