[1.5.x] Fixed #19525 -- Reverted dcd4383107 and 05d333ba3b.

Refs #9893, #18515.

Thanks Russell for the report.

Backport of db278c3 from master.

django/db/models/fields/files.py

@@ -3,7 +3,6 @@ import os
 
 from django import forms
 from django.db.models.fields import Field
-from django.core.exceptions import ValidationError
 from django.core.files.base import File
 from django.core.files.storage import default_storage
 from django.core.files.images import ImageFile
@@ -207,10 +206,6 @@ class FileDescriptor(object):
 
 class FileField(Field):
 
-    default_error_messages = {
-        'max_length': _('Filename is %(extra)d characters too long.')
-    }
-
     # The class to wrap instance attributes in. Accessing the file object off
     # the instance will always return an instance of attr_class.
     attr_class = FieldFile
@@ -233,25 +228,6 @@ class FileField(Field):
         kwargs['max_length'] = kwargs.get('max_length', 100)
         super(FileField, self).__init__(verbose_name, name, **kwargs)
 
-    def validate(self, value, model_instance):
-        """
-        Validates that the generated file name still fits within max_length.
-        """
-        # The generated file name stored in the database is generally longer
-        # than the uploaded file name. Using the length of generated name in
-        # the error message would be confusing. However, in the common case
-        # (ie. upload_to='path/to/upload/dir'), the length of the generated
-        # name equals the length of the uploaded name plus a constant. Thus
-        # we can tell the user how much shorter the name should be (roughly).
-        if value and value._committed:
-            filename = value.name
-        else:
-            filename = self.generate_filename(model_instance, value.name)
-        length = len(filename)
-        if self.max_length and length > self.max_length:
-            error_values = {'extra': length - self.max_length}
-            raise ValidationError(self.error_messages['max_length'] % error_values)
-
     def get_internal_type(self):
         return "FileField"
 

tests/modeltests/files/models.py

@@ -26,5 +26,5 @@ class Storage(models.Model):
 
     normal = models.FileField(storage=temp_storage, upload_to='tests')
     custom = models.FileField(storage=temp_storage, upload_to=custom_upload_to)
-    random = models.FileField(storage=temp_storage, upload_to=random_upload_to, max_length=16)
+    random = models.FileField(storage=temp_storage, upload_to=random_upload_to)
     default = models.FileField(storage=temp_storage, upload_to='tests', default='tests/default.txt')

tests/modeltests/files/tests.py

@@ -5,7 +5,6 @@ import shutil
 import tempfile
 
 from django.core.cache import cache
-from django.core.exceptions import ValidationError
 from django.core.files import File
 from django.core.files.base import ContentFile
 from django.core.files.uploadedfile import SimpleUploadedFile
@@ -103,24 +102,6 @@ class FileStorageTests(TestCase):
         obj4.random.save("random_file", ContentFile("random content"))
         self.assertTrue(obj4.random.name.endswith("/random_file"))
 
-    def test_max_length(self):
-        """
-        Test that FileField validates the length of the generated file name
-        that will be stored in the database. Regression for #9893.
-        """
-        # upload_to = 'unused', so file names are saved as '456/xxxxx'.
-        # max_length = 16, so names longer than 12 characters are rejected.
-        s1 = Storage(random=SimpleUploadedFile(12 * 'x', b"content"))
-        s1.full_clean()
-        with self.assertRaises(ValidationError):
-            Storage(random=SimpleUploadedFile(13 * 'x', b"content")).full_clean()
-
-        # Ticket #18515: validation for an already saved file should not check
-        # against a regenerated file name (and potentially raise a ValidationError
-        # if max_length is exceeded
-        s1.save()
-        s1.full_clean()
-
 
 class FileTests(unittest.TestCase):
     def test_context_manager(self):