fixed the file handling implementation. The feature is cool, but the original implementation had so many small flaws it wasn't even funny.

src/documents/file_handling.py

@@ -0,0 +1,92 @@
+import os
+from collections import defaultdict
+
+from django.conf import settings
+from django.template.defaultfilters import slugify
+
+
+def create_source_path_directory(source_path):
+    os.makedirs(os.path.dirname(source_path), exist_ok=True)
+
+
+def delete_empty_directories(directory):
+    # Go up in the directory hierarchy and try to delete all directories
+    directory = os.path.normpath(directory)
+    root = os.path.normpath(settings.ORIGINALS_DIR)
+
+    if not directory.startswith(root + os.path.sep):
+        # don't do anything outside our originals folder.
+
+        # append os.path.set so that we avoid these cases:
+        #   directory = /home/originals2/test
+        #   root = /home/originals ("/" gets appended and startswith fails)
+        return
+
+    while directory != root:
+        if not os.listdir(directory):
+            # it's empty
+            try:
+                os.rmdir(directory)
+            except OSError:
+                # whatever. empty directories aren't that bad anyway.
+                return
+        else:
+            # it's not empty.
+            return
+
+        # go one level up
+        directory = os.path.normpath(os.path.dirname(directory))
+
+
+def many_to_dictionary(field):
+    # Converts ManyToManyField to dictionary by assuming, that field
+    # entries contain an _ or - which will be used as a delimiter
+    mydictionary = dict()
+
+    for index, t in enumerate(field.all()):
+        # Populate tag names by index
+        mydictionary[index] = slugify(t.name)
+
+        # Find delimiter
+        delimiter = t.name.find('_')
+
+        if delimiter == -1:
+            delimiter = t.name.find('-')
+
+        if delimiter == -1:
+            continue
+
+        key = t.name[:delimiter]
+        value = t.name[delimiter + 1:]
+
+        mydictionary[slugify(key)] = slugify(value)
+
+    return mydictionary
+
+
+def generate_filename(document):
+    # Create filename based on configured format
+    if settings.PAPERLESS_FILENAME_FORMAT is not None:
+        tags = defaultdict(lambda: slugify(None),
+                           many_to_dictionary(document.tags))
+        path = settings.PAPERLESS_FILENAME_FORMAT.format(
+            correspondent=slugify(document.correspondent),
+            title=slugify(document.title),
+            created=document.created.date(),
+            added=slugify(document.added),
+            tags=tags,
+        )
+    else:
+        path = ""
+
+    # Always append the primary key to guarantee uniqueness of filename
+    if len(path) > 0:
+        filename = "%s-%07i.%s" % (path, document.pk, document.file_type)
+    else:
+        filename = "%07i.%s" % (document.pk, document.file_type)
+
+    # Append .gpg for encrypted files
+    if document.storage_type == document.STORAGE_TYPE_GPG:
+        filename += ".gpg"
+
+    return filename