Markdown notes fix (#3946)

* Improve 'remove_non_printable_characters' method in helpers.py

- Requires fancy 'negative-lookahead' regex to negate existing unicode regex

* Adds  extra test for markdown fields

- Ensure that newline characters are retained
- Very necessary for markdown formatting!
- Update field cleaning to allow newlines in some very specific cases

* Bug fix

* Better edge case handling

InvenTree/InvenTree/helpers.py

@@ -950,16 +950,27 @@ def strip_html_tags(value: str, raise_error=True, field_name=None):
     return cleaned
 
 
-def remove_non_printable_characters(value: str, remove_ascii=True, remove_unicode=True):
+def remove_non_printable_characters(value: str, remove_newline=True, remove_ascii=True, remove_unicode=True):
     """Remove non-printable / control characters from the provided string"""
 
+    cleaned = value
+
     if remove_ascii:
         # Remove ASCII control characters
-        cleaned = regex.sub(u'[\x01-\x1F]+', '', value)
+        # Note that we do not sub out 0x0A (\n) here, it is done separately below
+        cleaned = regex.sub(u'[\x01-\x09]+', '', cleaned)
+        cleaned = regex.sub(u'[\x0b-\x1F]+', '', cleaned)
+
+    if remove_newline:
+        cleaned = regex.sub(u'[\x0a]+', '', cleaned)
 
     if remove_unicode:
         # Remove Unicode control characters
-        cleaned = regex.sub(u'[^\P{C}]+', '', value)
+        if remove_newline:
+            cleaned = regex.sub(u'[^\P{C}]+', '', cleaned)
+        else:
+            # Use 'negative-lookahead' to exclude newline character
+            cleaned = regex.sub(u'(?![\x0A])[^\P{C}]+', '', cleaned)
 
     return cleaned
 

InvenTree/InvenTree/mixins.py

@@ -1,8 +1,11 @@
 """Mixins for (API) views in the whole project."""
 
+from django.core.exceptions import FieldDoesNotExist
+
 from rest_framework import generics, mixins, status
 from rest_framework.response import Response
 
+from InvenTree.fields import InvenTreeNotesField
 from InvenTree.helpers import remove_non_printable_characters, strip_html_tags
 
 
@@ -44,10 +47,35 @@ class CleanMixin():
         Nominally, the only thing that will be "cleaned" will be HTML tags
 
         Ref: https://github.com/mozilla/bleach/issues/192
+
         """
 
         cleaned = strip_html_tags(data, field_name=field)
-        cleaned = remove_non_printable_characters(cleaned)
+
+        # By default, newline characters are removed
+        remove_newline = True
+
+        try:
+            if hasattr(self, 'serializer_class'):
+                model = self.serializer_class.Meta.model
+                field = model._meta.get_field(field)
+
+                # The following field types allow newline characters
+                allow_newline = [
+                    InvenTreeNotesField,
+                ]
+
+                for field_type in allow_newline:
+                    if issubclass(type(field), field_type):
+                        remove_newline = False
+                        break
+
+        except AttributeError:
+            pass
+        except FieldDoesNotExist:
+            pass
+
+        cleaned = remove_non_printable_characters(cleaned, remove_newline=remove_newline)
 
         return cleaned
 

InvenTree/part/test_api.py

@@ -1598,8 +1598,24 @@ class PartDetailTests(InvenTreeAPITestCase):
         self.assertFalse('hello' in part.metadata)
         self.assertEqual(part.metadata['x'], 'y')
 
-    def test_part_notes(self):
-        """Unit tests for the part 'notes' field"""
+
+class PartNotesTests(InvenTreeAPITestCase):
+    """Tests for the 'notes' field (markdown field)"""
+
+    fixtures = [
+        'category',
+        'part',
+        'location',
+        'company',
+    ]
+
+    roles = [
+        'part.change',
+        'part.add',
+    ]
+
+    def test_long_notes(self):
+        """Test that very long notes field is rejected"""
 
         # Ensure that we cannot upload a very long piece of text
         url = reverse('api-part-detail', kwargs={'pk': 1})
@@ -1614,6 +1630,36 @@ class PartDetailTests(InvenTreeAPITestCase):
 
         self.assertIn('Ensure this field has no more than 50000 characters', str(response.data['notes']))
 
+    def test_multiline_formatting(self):
+        """Ensure that markdown formatting is retained"""
+
+        url = reverse('api-part-detail', kwargs={'pk': 1})
+
+        notes = """
+        ### Title
+
+        1. Numbered list
+        2. Another item
+        3. Another item again
+
+        [A link](http://link.com.go)
+
+        """
+
+        response = self.patch(
+            url,
+            {
+                'notes': notes,
+            },
+            expected_code=200
+        )
+
+        # Ensure that newline chars have not been removed
+        self.assertIn('\n', response.data['notes'])
+
+        # Entire notes field should match original value
+        self.assertEqual(response.data['notes'], notes.strip())
+
 
 class PartPricingDetailTests(InvenTreeAPITestCase):
     """Tests for the part pricing API endpoint"""