Changes to ImageFileDescriptor and ImageField to fix a few cases of setting image dimension fields.

* Moved dimension field update logic out of `ImageFileDescriptor.__set__` and into its own method on `ImageField`.
 * New `ImageField.update_dimension_fields` method is attached to model instance's `post_init` signal so that:
   * Dimension fields are set when defined before the ImageField.
   * Dimension fields are set when the field is assigned in the model constructor (fixes #11196), but only if the dimension fields don't already have values, so we avoid updating the dimensions every time an object is loaded from the database (fixes #11084).
 * Clear dimension fields when the ImageField is set to None, which also causes dimension fields to be cleared when `ImageFieldFile.delete()` is used.
 * Added many more tests for ImageField that test edge cases we weren't testing before, and moved the ImageField tests out of `file_storage` and into their own module within `model_fields`.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@10858 bcc190cf-cafb-0310-a4f2-bffc1f526a37

tests/regressiontests/model_fields/tests.py

@@ -6,13 +6,26 @@ from django import forms
 from django.db import models
 from django.core.exceptions import ValidationError
 
-from models import Foo, Bar, Whiz, BigD, BigS
+from models import Foo, Bar, Whiz, BigD, BigS, Image
 
 try:
     from decimal import Decimal
 except ImportError:
     from django.utils._decimal import Decimal
 
+
+# If PIL available, do these tests.
+if Image:
+    from imagefield import \
+            ImageFieldTests, \
+            ImageFieldTwoDimensionsTests, \
+            ImageFieldNoDimensionsTests, \
+            ImageFieldOneDimensionTests, \
+            ImageFieldDimensionsFirstTests, \
+            ImageFieldUsingFileTests, \
+            TwoImageFieldTests
+
+
 class DecimalFieldTests(django.test.TestCase):
     def test_to_python(self):
         f = models.DecimalField(max_digits=4, decimal_places=2)
@@ -131,4 +144,3 @@ class SlugFieldTests(django.test.TestCase):
         bs = BigS.objects.create(s = 'slug'*50)
         bs = BigS.objects.get(pk=bs.pk)
         self.assertEqual(bs.s, 'slug'*50)
-