Django integration tests

[ColeDCrawford]

This PR sets up a test Django project implementing EDTFField and adding Django integration tests. It also adds an additional class attribute direct_input_field to EDTFField so users have the option to provide an EDTF string directly instead of or in addition to using natural_field_text. If both natural_field_text and direct_input_field are provided, direct_input_text supersedes it for date generation; natural_field_text can still be used as a label. If only direct_input_field is provided, then natural_field_text is filled with the EDTF string.

This PR should be merged after the pytest PR.

[aweakley]

Thanks very much for this.

I've been looking at your comment on fbf4262 about the failing test.

I found that if I move the definition of date_display on the model down below the definition of date_edtf then it works. I think the cause is that here: https://github.com/django/django/blob/d26c8838d0a447d5cba03a0b4eebd5fc2d27e9df/django/db/models/sql/compiler.py#L1747 it's calling pre_save on each field in order and saving the result. So it's already stored the empty value of date_display before that value is populated by the pre_save of the date_edtf field.

In ImageField they do a similar thing to populate the width and height fields by attaching a signal handler to post_init. I wonder if we should move some of the pre_save processing into something like that?

[aweakley]

... oh, post_init isn't the full story - the update-fields method is also called by the __set__ method of the file descriptor - that makes more sense, I was wondering how post_init would capture every change.

[aweakley]

Something like this maybe?

diff --git a/edtf/fields.py b/edtf/fields.py
index bbccbcf..325b5aa 100644
--- a/edtf/fields.py
+++ b/edtf/fields.py
@@ -3,12 +3,14 @@ try:
 except:
     import pickle
 
-from django.db import models
 from django.core.exceptions import FieldDoesNotExist
+from django.db import models
+from django.db.models import signals
+from django.db.models.query_utils import DeferredAttribute
 
 from edtf import parse_edtf, EDTFObject
-from edtf.natlang import text_to_edtf
 from edtf.convert import struct_time_to_date, struct_time_to_jd
+from edtf.natlang import text_to_edtf
 
 DATE_ATTRS = (
     'lower_strict',
@@ -17,6 +19,20 @@ DATE_ATTRS = (
     'upper_fuzzy',
 )
 
+class EDTFFieldDescriptor(DeferredAttribute):
+    """
+    Descriptor for the EDTFField's attribute on the model instance.
+    This updates the dependent fields each time this value is set.
+    """
+
+    def __set__(self, instance, value):
+        # First set the value we are given
+        instance.__dict__[self.field.attname] = value
+        # `update_values` may provide us with a new value to set
+        edtf = self.field.update_values(instance, value)
+        if edtf != value:
+            instance.__dict__[self.field.attname] = edtf
+
 
 class EDTFField(models.CharField):
 
@@ -40,6 +56,7 @@ class EDTFField(models.CharField):
         super(EDTFField, self).__init__(verbose_name, name, **kwargs)
 
     description = "A field for storing complex/fuzzy date specifications in EDTF format."
+    descriptor_class = EDTFFieldDescriptor
 
     def deconstruct(self):
         name, path, args, kwargs = super(EDTFField, self).deconstruct()
@@ -88,14 +105,14 @@ class EDTFField(models.CharField):
             return pickle.dumps(value)
         return value
 
-    def pre_save(self, instance, add):
+    def update_values(self, instance, *args, **kwargs):
         """
         Updates the EDTF value from either the natural_text_field, which is parsed
         with text_to_edtf() and is used for display, or falling back to the direct_input_field,
         which allows directly providing an EDTF string. If one of these provides a valid EDTF object,
         then set the date values accordingly.
         """
-    
+
         # Get existing value to determine if update is needed
         existing_value = getattr(instance, self.attname, None)
         direct_input = getattr(instance, self.direct_input_field, None)
@@ -123,10 +140,6 @@ class EDTFField(models.CharField):
             # TODO: if both direct_input and natural_text are cleared, should we throw an error?
             edtf = existing_value
 
-        # Update the actual EDTF field in the model if there is a change
-        if edtf != existing_value:
-            setattr(instance, self.attname, edtf)
-
         # Process and update related date fields based on the EDTF object
         for attr in DATE_ATTRS:
             field_attr = f"{attr}_field"
@@ -151,3 +164,12 @@ class EDTFField(models.CharField):
                 else:
                     setattr(instance, g, None)
         return edtf
+
+    def contribute_to_class(self, cls, name, **kwargs):
+        super().contribute_to_class(cls, name, **kwargs)
+        # Attach update_values so that dependent fields declared
+        # after their corresponding edtf field don't stay cleared by
+        # Model.__init__, see Django bug #11196.
+        # Only run post-initialization values update on non-abstract models
+        if not cls._meta.abstract:
+            signals.post_init.connect(self.update_values, sender=cls)
diff --git a/edtf_django_tests/edtf_integration/tests.py b/edtf_django_tests/edtf_integration/tests.py
index de54d64..e0b80f9 100644
--- a/edtf_django_tests/edtf_integration/tests.py
+++ b/edtf_django_tests/edtf_integration/tests.py
@@ -73,9 +73,8 @@ class TestEventModelTests(TestCase):
         In the future, a more sophisticated natural language parser could be used to generate
         a human readable date from the EDTF input.
         """
-        # why does this fail??
-        # event = TestEvent.objects.get(date_edtf_direct="2020-03-15/2020-04-15")
-        # self.assertEqual(event.date_display, "2020-03-15/2020-04-15")
+        event = TestEvent.objects.get(date_edtf_direct="2020-03-15/2020-04-15")
+        self.assertEqual(event.date_display, "2020-03-15/2020-04-15")
 
         self.assertEqual(self.event1.date_display, "2020-03-15/2020-04-15")
         self.assertEqual(self.event2.date_display, "2021-05-06")
@@ -93,4 +92,4 @@ class TestEventModelTests(TestCase):
         self.assertGreater(self.event2.date_edtf, self.event3.date_edtf, "2021-05-06 is greater than 2019-11")
 
         # less than
-        self.assertLess(self.event3.date_edtf, self.event2.date_edtf, "2019-11 is less than 2021-05-06")
\ No newline at end of file
+        self.assertLess(self.event3.date_edtf, self.event2.date_edtf, "2019-11 is less than 2021-05-06")

[aweakley]

Great, thanks very much.