From 53c86c30a1a1590e323555954516ff0949bc0c9f Mon Sep 17 00:00:00 2001
From: Ethan Dalool <git@voussoir.net>
Date: Sat, 11 Aug 2018 18:19:55 -0700
Subject: [PATCH] Improve clarity of the recursive_dict_ helper functions &
 usage.

---
 etiquette/helpers.py | 20 +++++++++++++-------
 etiquette/photodb.py |  9 +++++++--
 2 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/etiquette/helpers.py b/etiquette/helpers.py
index 91a576b..99fbe89 100644
--- a/etiquette/helpers.py
+++ b/etiquette/helpers.py
@@ -325,7 +325,17 @@ def read_filebytes(filepath, range_min=0, range_max=None, chunk_size=bytestring.
 def recursive_dict_update(target, supply):
     '''
     Update target using supply, but when the value is a dictionary update the
-    insides instead of replacing the dictionary itself.
+    insides instead of replacing the dictionary itself. This prevents keys that
+    exist in the target but don't exist in the supply from being erased.
+    Note that we are modifying target in place.
+
+    eg:
+    target = {'hi': 'ho', 'neighbor': {'name': 'Wilson'}}
+    supply = {'neighbor': {'behind': 'fence'}}
+
+    result: {'hi': 'ho', 'neighbor': {'name': 'Wilson', 'behind': 'fence'}}
+    whereas a regular dict.update would have produced:
+    {'hi': 'ho', 'neighbor': {'behind': 'fence'}}
     '''
     for (key, value) in supply.items():
         if isinstance(value, dict):
@@ -333,7 +343,7 @@ def recursive_dict_update(target, supply):
             if existing is None:
                 target[key] = value
             else:
-                recursive_dict_update(existing, value)
+                recursive_dict_update(target=existing, supply=value)
         else:
             target[key] = value
 
@@ -343,11 +353,7 @@ def recursive_dict_keys(d):
     all other dictionaries that appear as values within. The subkeys will use \\
     to indicate their lineage.
 
-    {
-        'hi': {
-            'ho': 'neighbor'
-        }
-    }
+    {'hi': {'ho': 'neighbor'}}
 
     returns
 
diff --git a/etiquette/photodb.py b/etiquette/photodb.py
index b3a7c34..8f41313 100644
--- a/etiquette/photodb.py
+++ b/etiquette/photodb.py
@@ -1530,9 +1530,14 @@ class PhotoDB(
         if user_config_exists:
             with open(self.config_filepath.absolute_path, 'r', encoding='utf-8') as handle:
                 user_config = json.load(handle)
-            my_keys = helpers.recursive_dict_keys(config)
+
+            # If the default config has been updated and contains new keys,
+            # then they will not yet exist in the user's config, and we should
+            # save the file after giving it those default values.
+            default_keys = helpers.recursive_dict_keys(config)
             stored_keys = helpers.recursive_dict_keys(user_config)
-            needs_dump = not my_keys.issubset(stored_keys)
+            needs_dump = default_keys > stored_keys
+
             helpers.recursive_dict_update(target=config, supply=user_config)
         else:
             needs_dump = True