Fix: consolidate and extend unicode NFC normalization for filenames and matching

Consolidates the scattered unicodedata.normalize("NFC", ...) calls introduced
by my earlier filename/path normalization work into a single
documents.utils.normalize_unicode() helper, and closes several gaps where
NFD-normalized filenames could still slip through unnormalized:

- Document.get_public_filename() now normalizes, fixing exported filenames
  built from an NFD title/correspondent name (the default, non-format export
  path was not covered by the earlier fix).
- DocumentViewSet.update_version() now normalizes the uploaded filename,
  matching PostDocumentView's existing behavior.
- ConsumerPlugin normalizes self.filename once at consumption time, covering
  the title fallback and Document.original_filename for every document
  source (consume folder, mail, API, barcode splits).
- Workflow trigger and mail rule filename/path matching (documents/matching.py,
  paperless_mail/mail.py) now normalize the document/attachment side before
  comparing, so an NFD filename matches an NFC-typed filter pattern instead of
  silently failing to match.
- WorkflowTriggerSerializer and MailRuleSerializer normalize filter_filename/
  filter_path and the attachment include/exclude patterns once at write time,
  so the read side isn't re-normalizing an already-canonical value on every
  match.

src/documents/consumer.py

@@ -52,6 +52,7 @@ from documents.templating.workflows import parse_w_workflow_placeholders
 from documents.utils import compute_checksum
 from documents.utils import copy_basic_file_stats
 from documents.utils import copy_file_with_basic_stats
+from documents.utils import normalize_unicode
 from documents.utils import run_subprocess
 from paperless.config import OcrConfig
 from paperless.config import RemoteOCRConfig
@@ -201,7 +202,9 @@ class ConsumerPluginMixin:
 
         self.renew_logging_group()
 
-        self.filename = self.metadata.filename or self.input_doc.original_file.name
+        self.filename = normalize_unicode(
+            self.metadata.filename or self.input_doc.original_file.name,
+        )
 
     def _send_progress(
         self,

src/documents/matching.py

@@ -21,6 +21,7 @@ from documents.models import Workflow
 from documents.models import WorkflowTrigger
 from documents.permissions import permitted_object_ids
 from documents.regex import safe_regex_search
+from documents.utils import normalize_unicode
 
 if TYPE_CHECKING:
     from django.db.models import QuerySet
@@ -311,11 +312,12 @@ def consumable_document_matches_workflow(
         trigger_matched = False
 
     # Document filename vs trigger filename
+    document_filename = normalize_unicode(document.original_file.name)
     if (
         trigger.filter_filename is not None
         and len(trigger.filter_filename) > 0
         and not fnmatch(
-            document.original_file.name.lower(),
+            document_filename.lower(),
             trigger.filter_filename.lower(),
         )
     ):
@@ -328,10 +330,12 @@ def consumable_document_matches_workflow(
     # Document path vs trigger path
 
     # Use the original_path if set, else us the original_file
-    match_against = (
+    match_against = normalize_unicode(
+        str(
             document.original_path
             if document.original_path is not None
-        else document.original_file
+            else document.original_file,
+        ),
     )
 
     if (
@@ -536,7 +540,7 @@ def existing_document_matches_workflow(
         and len(trigger.filter_filename) > 0
         and document.original_filename is not None
         and not fnmatch(
-            document.original_filename.lower(),
+            normalize_unicode(document.original_filename).lower(),
             trigger.filter_filename.lower(),
         )
     ):

src/documents/models.py

@@ -27,6 +27,7 @@ from django_softdelete.models import SoftDeleteModel
 
 from documents.data_models import DocumentSource
 from documents.parsers import get_default_file_extension
+from documents.utils import normalize_unicode
 
 
 class ModelWithOwner(models.Model):
@@ -467,7 +468,7 @@ class Document(SoftDeleteModel, ModelWithOwner):  # type: ignore[django-manager-
         context_document = (
             self.root_document if self.root_document_id is not None else self
         )
-        result = str(context_document)
+        result = normalize_unicode(str(context_document))
 
         if counter:
             result += f"_{counter:02}"

src/documents/serialisers.py

@@ -87,6 +87,7 @@ from documents.regex import validate_regex_pattern
 from documents.templating.filepath import validate_filepath_template_and_render
 from documents.templating.utils import convert_format_str_to_template_format
 from documents.templating.workflows import validate_workflow_template
+from documents.utils import normalize_unicode
 from documents.validators import uri_validator
 from documents.validators import url_validator
 from documents.versioning import sort_versions_newest_first
@@ -3120,6 +3121,13 @@ class WorkflowTriggerSerializer(serializers.ModelSerializer[WorkflowTrigger]):
         ):
             attrs["filter_path"] = None
 
+        # Normalize once at write time, since these are matched against many
+        # documents but edited rarely
+        if attrs.get("filter_filename") is not None:
+            attrs["filter_filename"] = normalize_unicode(attrs["filter_filename"])
+        if attrs.get("filter_path") is not None:
+            attrs["filter_path"] = normalize_unicode(attrs["filter_path"])
+
         if (
             "filter_custom_field_query" in attrs
             and attrs["filter_custom_field_query"] is not None

src/documents/templating/filepath.py

@@ -1,7 +1,6 @@
 import logging
 import os
 import re
-import unicodedata
 from collections.abc import Iterable
 from pathlib import PurePath
 
@@ -26,6 +25,7 @@ from documents.templating.environment import _template_environment
 from documents.templating.filters import format_datetime
 from documents.templating.filters import get_cf_value
 from documents.templating.filters import localize_date
+from documents.utils import normalize_unicode
 
 logger = logging.getLogger("paperless.templating")
 
@@ -42,7 +42,7 @@ class FilePathTemplate(Template):
             3. Removing extra spaces before and after forward slashes
             4. Preserving spaces in other parts of the path
             """
-            value = unicodedata.normalize("NFC", value)
+            value = normalize_unicode(value)
             value = value.replace("\n", "").replace("\r", "")
             value = re.sub(r"\s*/\s*", "/", value)
 
@@ -184,17 +184,17 @@ def get_basic_metadata_context(
     """
     return {
         "title": pathvalidate.sanitize_filename(
-            unicodedata.normalize("NFC", document.title),
+            normalize_unicode(document.title),
             replacement_text="-",
         ),
         "correspondent": pathvalidate.sanitize_filename(
-            unicodedata.normalize("NFC", document.correspondent.name),
+            normalize_unicode(document.correspondent.name),
             replacement_text="-",
         )
         if document.correspondent
         else no_value_default,
         "document_type": pathvalidate.sanitize_filename(
-            unicodedata.normalize("NFC", document.document_type.name),
+            normalize_unicode(document.document_type.name),
             replacement_text="-",
         )
         if document.document_type
@@ -205,8 +205,7 @@ def get_basic_metadata_context(
         "owner_username": document.owner.username
         if document.owner
         else no_value_default,
-        "original_name": unicodedata.normalize(
-            "NFC",
+        "original_name": normalize_unicode(
             PurePath(document.original_filename).with_suffix("").name,
         )
         if document.original_filename
@@ -275,12 +274,12 @@ def get_tags_context(tags: Iterable[Tag]) -> dict[str, str | list[str]]:
     return {
         "tag_list": pathvalidate.sanitize_filename(
             ",".join(
-                sorted(unicodedata.normalize("NFC", tag.name) for tag in tags),
+                sorted(normalize_unicode(tag.name) for tag in tags),
             ),
             replacement_text="-",
         ),
         # Assumed to be ordered, but a template could loop through to find what they want
-        "tag_name_list": [unicodedata.normalize("NFC", x.name) for x in tags],
+        "tag_name_list": [normalize_unicode(x.name) for x in tags],
     }
 
 
@@ -307,7 +306,7 @@ def get_custom_fields_context(
             CustomField.FieldDataType.LONG_TEXT,
         }:
             value = pathvalidate.sanitize_filename(
-                unicodedata.normalize("NFC", field_instance.value),
+                normalize_unicode(field_instance.value),
                 replacement_text="-",
             )
         elif (
@@ -316,8 +315,7 @@ def get_custom_fields_context(
         ):
             options = field_instance.field.extra_data["select_options"]
             value = pathvalidate.sanitize_filename(
-                unicodedata.normalize(
-                    "NFC",
+                normalize_unicode(
                     next(
                         option["label"]
                         for option in options
@@ -330,7 +328,7 @@ def get_custom_fields_context(
             value = field_instance.value
         field_data["custom_fields"][
             pathvalidate.sanitize_filename(
-                unicodedata.normalize("NFC", field_instance.field.name),
+                normalize_unicode(field_instance.field.name),
                 replacement_text="-",
             )
         ] = {

src/documents/tests/test_api_update_version_nfc.py

@@ -0,0 +1,69 @@
+import unicodedata
+from typing import TYPE_CHECKING
+from unittest import mock
+
+import celery.result
+import pytest
+from django.core.files.uploadedfile import SimpleUploadedFile
+
+from documents.models import Document
+
+if TYPE_CHECKING:
+    from documents.data_models import ConsumableDocument
+
+
+@pytest.fixture()
+def consume_file_mock():
+    with mock.patch("documents.tasks.consume_file.apply_async") as m:
+        m.return_value = celery.result.AsyncResult(id="test-task-id")
+        yield m
+
+
+@pytest.fixture()
+def directories(tmp_path, settings, _media_settings):
+    scratch = tmp_path / "scratch"
+    scratch.mkdir()
+    settings.SCRATCH_DIR = scratch
+    return scratch
+
+
+@pytest.mark.django_db
+class TestUpdateVersionNFCNormalization:
+    def test_nfd_filename_normalized_to_nfc(
+        self,
+        admin_client,
+        consume_file_mock: mock.MagicMock,
+        directories,
+    ):
+        """Uploaded new-version file with NFD filename must have its temp name stored as NFC."""
+        document = Document.objects.create(
+            title="Test",
+            content="content",
+            checksum="checksum",
+            mime_type="application/pdf",
+        )
+
+        nfd = unicodedata.normalize("NFD", "Rechnung März.pdf")
+        nfc = unicodedata.normalize("NFC", "Rechnung März.pdf")
+
+        assert nfd != nfc
+
+        uploaded = SimpleUploadedFile(
+            nfd,
+            b"%PDF-1.4 test",
+            content_type="application/pdf",
+        )
+        response = admin_client.post(
+            f"/api/documents/{document.pk}/update_version/",
+            {"document": uploaded},
+        )
+
+        assert response.status_code == 200
+
+        task_kwargs = consume_file_mock.call_args.kwargs["kwargs"]
+        input_doc: ConsumableDocument = task_kwargs["input_doc"]
+
+        assert input_doc.original_file.name == nfc, (
+            f"Expected NFC filename {nfc!r}, got {input_doc.original_file.name!r}"
+        )
+        assert unicodedata.is_normalized("NFC", input_doc.original_file.name)

src/documents/tests/test_get_public_filename_nfc.py

@@ -0,0 +1,48 @@
+import unicodedata
+from datetime import date
+
+import pytest
+
+from documents.models import Correspondent
+from documents.models import Document
+
+
+@pytest.mark.django_db
+class TestGetPublicFilenameNfc:
+    def test_normalizes_nfd_title_to_nfc(self) -> None:
+        nfd_title = unicodedata.normalize("NFD", "Gehaltserhöhung")
+        assert not unicodedata.is_normalized("NFC", nfd_title)
+
+        doc = Document(
+            mime_type="application/pdf",
+            title=nfd_title,
+            created=date(2025, 10, 17),
+        )
+
+        result = doc.get_public_filename()
+
+        assert unicodedata.is_normalized("NFC", result)
+        assert (
+            result
+            == "2025-10-17 "
+            + unicodedata.normalize(
+                "NFC",
+                nfd_title,
+            )
+            + ".pdf"
+        )
+
+    def test_normalizes_nfd_correspondent_name_to_nfc(self) -> None:
+        nfd_name = unicodedata.normalize("NFD", "Müller GmbH")
+        correspondent = Correspondent.objects.create(name=nfd_name)
+
+        doc = Document.objects.create(
+            mime_type="application/pdf",
+            title="Rechnung",
+            created=date(2025, 10, 17),
+            correspondent=correspondent,
+        )
+
+        result = doc.get_public_filename()
+
+        assert unicodedata.is_normalized("NFC", result)

src/documents/tests/test_matching_nfc.py

@@ -0,0 +1,80 @@
+import unicodedata
+
+import pytest
+
+from documents.data_models import ConsumableDocument
+from documents.data_models import DocumentSource
+from documents.matching import consumable_document_matches_workflow
+from documents.matching import existing_document_matches_workflow
+from documents.models import Document
+from documents.models import Workflow
+from documents.models import WorkflowTrigger
+
+
+@pytest.mark.django_db
+class TestMatchingNfcNormalization:
+    def test_consumable_document_filename_nfd_matches_nfc_pattern(
+        self,
+        tmp_path,
+    ) -> None:
+        """
+        GIVEN:
+            - A file on disk whose name is NFD-normalized
+            - A workflow trigger filename filter typed as NFC
+        WHEN:
+            - The consumable document is checked against the trigger
+        THEN:
+            - It matches, because both sides are normalized before comparing
+        """
+        nfd_name = unicodedata.normalize("NFD", "Gehaltserhöhung.pdf")
+        nfc_pattern = unicodedata.normalize("NFC", "*Gehaltserhöhung*")
+        assert nfd_name != unicodedata.normalize("NFC", nfd_name)
+
+        file_path = tmp_path / nfd_name
+        file_path.write_bytes(b"%PDF-1.4 test")
+
+        document = ConsumableDocument(
+            source=DocumentSource.ConsumeFolder,
+            original_file=file_path,
+        )
+        trigger = WorkflowTrigger(
+            type=WorkflowTrigger.WorkflowTriggerType.CONSUMPTION,
+            filter_filename=nfc_pattern,
+            sources=[],
+        )
+
+        matched, reason = consumable_document_matches_workflow(document, trigger)
+
+        assert matched, reason
+
+    def test_existing_document_filename_nfd_matches_nfc_pattern(self) -> None:
+        """
+        GIVEN:
+            - A Document whose original_filename is NFD-normalized (e.g. from
+              before normalization was applied at consumption time)
+            - A workflow trigger filename filter typed as NFC
+        WHEN:
+            - The document is checked against the trigger
+        THEN:
+            - It matches, because both sides are normalized before comparing
+        """
+        nfd_name = unicodedata.normalize("NFD", "Gehaltserhöhung.pdf")
+        nfc_pattern = unicodedata.normalize("NFC", "*Gehaltserhöhung*")
+
+        document = Document.objects.create(
+            title="Test",
+            content="content",
+            checksum="checksum",
+            mime_type="application/pdf",
+            original_filename=nfd_name,
+        )
+        workflow = Workflow.objects.create(name="Test workflow", order=0)
+        trigger = WorkflowTrigger.objects.create(
+            type=WorkflowTrigger.WorkflowTriggerType.DOCUMENT_ADDED,
+            filter_filename=nfc_pattern,
+        )
+        workflow.triggers.add(trigger)
+
+        matched, reason = existing_document_matches_workflow(document, trigger)
+
+        assert matched, reason

src/documents/tests/test_normalize_unicode.py

@@ -0,0 +1,6 @@
+from documents.utils import normalize_unicode
+
+
+class TestNormalizeUnicode:
+    def test_none_passes_through(self) -> None:
+        assert normalize_unicode(None) is None

src/documents/utils.py

@@ -1,6 +1,7 @@
 import hashlib
 import logging
 import shutil
+import unicodedata
 from collections.abc import Callable
 from collections.abc import Iterable
 from collections.abc import Iterator
@@ -31,6 +32,25 @@ def identity(iterable: Iterable[_T]) -> Iterable[_T]:
     return iterable
 
 
+def normalize_unicode(value: str | None) -> str | None:
+    """
+    Normalize a string to Unicode NFC form, or return None unchanged.
+
+    This is the single normalization pass for any user- or filesystem-supplied
+    text that ends up in a filename, path, or is compared/matched against one
+    (titles, correspondent/tag/type names, uploaded filenames, workflow and
+    mail rule filename/path filters). Composed (NFC) and decomposed (NFD)
+    forms of the same visible text are different byte sequences, which breaks
+    exact comparisons and filesystem lookups even though the text looks
+    identical. Always normalize through this function rather than calling
+    unicodedata.normalize() directly, so every call site agrees on the same
+    form.
+    """
+    if value is None:
+        return None
+    return unicodedata.normalize("NFC", value)
+
+
 class QuerySetStream(Generic[_M]):
     """Stream a QuerySet via .iterator(chunk_size=...) instead of
     materializing it (plus any prefetch caches) all at once, while still

src/documents/views.py

@@ -231,6 +231,7 @@ from documents.tasks import sanity_check
 from documents.tasks import train_classifier
 from documents.tasks import update_document_parent_tags
 from documents.utils import get_boolean
+from documents.utils import normalize_unicode
 from documents.versioning import VersionResolutionError
 from documents.versioning import annotate_effective_content
 from documents.versioning import get_latest_version_for_root
@@ -2068,6 +2069,7 @@ class DocumentViewSet(
 
         try:
             doc_name, doc_data = serializer.validated_data.get("document")
+            doc_name = normalize_unicode(doc_name)
             version_label = serializer.validated_data.get("version_label")
 
             t = int(mktime(datetime.now().timetuple()))
@@ -3334,7 +3336,7 @@ class PostDocumentView(GenericAPIView[Any]):
         serializer.is_valid(raise_exception=True)
 
         doc_name, doc_data = serializer.validated_data.get("document")
-        doc_name = normalize("NFC", doc_name)
+        doc_name = normalize_unicode(doc_name)
         correspondent_id = serializer.validated_data.get("correspondent")
         document_type_id = serializer.validated_data.get("document_type")
         storage_path_id = serializer.validated_data.get("storage_path")

src/paperless_mail/mail.py

@@ -6,7 +6,6 @@ import socket
 import ssl
 import tempfile
 import traceback
-import unicodedata
 from datetime import date
 from datetime import timedelta
 from fnmatch import fnmatch
@@ -45,6 +44,7 @@ from documents.models import Correspondent
 from documents.models import PaperlessTask
 from documents.parsers import is_mime_type_supported
 from documents.tasks import consume_file
+from documents.utils import normalize_unicode
 from paperless.network import is_public_ip
 from paperless.network import resolve_hostname_ips
 from paperless_mail.models import MailAccount
@@ -617,10 +617,10 @@ class MailAccountHandler(LoggingMixin):
         rule: MailRule,
     ) -> str | None:
         if rule.assign_title_from == MailRule.TitleSource.FROM_SUBJECT:
-            return unicodedata.normalize("NFC", message.subject)
+            return normalize_unicode(message.subject)
 
         elif rule.assign_title_from == MailRule.TitleSource.FROM_FILENAME:
-            return unicodedata.normalize("NFC", Path(att.filename).stem)
+            return normalize_unicode(Path(att.filename).stem)
 
         elif rule.assign_title_from == MailRule.TitleSource.NONE:
             return None
@@ -1004,6 +1004,8 @@ class MailAccountHandler(LoggingMixin):
         consume_tasks = []
 
         for att in message.attachments:
+            attachment_filename = normalize_unicode(att.filename)
+
             if (
                 att.content_disposition != "attachment"
                 and rule.attachment_type
@@ -1018,7 +1020,7 @@ class MailAccountHandler(LoggingMixin):
 
             if not self.filename_inclusion_matches(
                 rule.filter_attachment_filename_include,
-                att.filename,
+                attachment_filename,
             ):
                 # Force the filename and pattern to the lowercase
                 # as this is system dependent otherwise
@@ -1030,7 +1032,7 @@ class MailAccountHandler(LoggingMixin):
                 continue
             elif self.filename_exclusion_matches(
                 rule.filter_attachment_filename_exclude,
-                att.filename,
+                attachment_filename,
             ):
                 self.log.debug(
                     f"Rule {rule}: "
@@ -1064,7 +1066,7 @@ class MailAccountHandler(LoggingMixin):
                 )
 
                 attachment_name = pathvalidate.sanitize_filename(
-                    unicodedata.normalize("NFC", att.filename),
+                    attachment_filename,
                 )
                 if attachment_name:
                     temp_filename = temp_dir / attachment_name
@@ -1175,7 +1177,7 @@ class MailAccountHandler(LoggingMixin):
         doc_overrides = DocumentMetadataOverrides(
             title=message.subject,
             filename=pathvalidate.sanitize_filename(
-                unicodedata.normalize("NFC", f"{message.subject}.eml"),
+                normalize_unicode(f"{message.subject}.eml"),
             ),
             correspondent_id=correspondent.id if correspondent else None,
             document_type_id=doc_type.id if doc_type else None,

src/paperless_mail/serialisers.py

@@ -8,6 +8,7 @@ from documents.serialisers import CorrespondentField
 from documents.serialisers import DocumentTypeField
 from documents.serialisers import OwnedObjectSerializer
 from documents.serialisers import TagsField
+from documents.utils import normalize_unicode
 from paperless_mail.models import MailAccount
 from paperless_mail.models import MailRule
 from paperless_mail.models import ProcessedMail
@@ -161,6 +162,12 @@ class MailRuleSerializer(OwnedObjectSerializer):
             raise serializers.ValidationError("Maximum mail age is unreasonably large.")
         return value
 
+    def validate_filter_attachment_filename_include(self, value):
+        return normalize_unicode(value)
+
+    def validate_filter_attachment_filename_exclude(self, value):
+        return normalize_unicode(value)
+
 
 class ProcessedMailSerializer(OwnedObjectSerializer):
     class Meta: