Fixed #12455 -- corrected an oversight in result_headers not honoring admin_order_field

This finishes some slightly refactoring that went into the admin_list
template tags.

Thanks to kegan for discovering the oversight.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@12157 bcc190cf-cafb-0310-a4f2-bffc1f526a37

tests/regressiontests/admin_util/tests.py

@@ -3,12 +3,15 @@ import unittest
 from django.db import models
 
 from django.contrib import admin
-from django.contrib.admin.util import display_for_field
+from django.contrib.admin.util import display_for_field, label_for_field
 from django.contrib.admin.views.main import EMPTY_CHANGELIST_VALUE
 
+from models import Article
+
 
 
 class UtilTests(unittest.TestCase):
+
     def test_null_display_for_field(self):
         """
         Regression test for #12550: display_for_field should handle None
@@ -38,3 +41,79 @@ class UtilTests(unittest.TestCase):
 
         display_value = display_for_field(None, models.FloatField())
         self.assertEqual(display_value, EMPTY_CHANGELIST_VALUE)
+
+    def test_label_for_field(self):
+        """
+        Tests for label_for_field
+        """
+        self.assertEquals(
+            label_for_field("title", Article),
+            "title"
+        )
+        self.assertEquals(
+            label_for_field("title2", Article),
+            "another name"
+        )
+        self.assertEquals(
+            label_for_field("title2", Article, return_attr=True), 
+            ("another name", None)
+        )
+
+        self.assertEquals(
+            label_for_field("__unicode__", Article),
+            "article"
+        )
+        self.assertEquals(
+            label_for_field("__str__", Article),
+            "article"
+        )
+
+        self.assertRaises(
+            AttributeError,
+            lambda: label_for_field("unknown", Article)
+        )
+
+        def test_callable(obj):
+            return "nothing"
+        self.assertEquals(
+            label_for_field(test_callable, Article),
+            "test_callable"
+        )
+        self.assertEquals(
+            label_for_field(test_callable, Article, return_attr=True),
+            ("test_callable", test_callable)
+        )
+
+        self.assertEquals(
+            label_for_field("test_from_model", Article),
+            "test_from_model"
+        )
+        self.assertEquals(
+            label_for_field("test_from_model", Article, return_attr=True),
+            ("test_from_model", Article.test_from_model)
+        )
+        self.assertEquals(
+            label_for_field("test_from_model_with_override", Article),
+            "not what you expect"
+        )
+
+        self.assertEquals(
+            label_for_field(lambda x: "nothing", Article),
+            "--"
+        )
+
+        class MockModelAdmin(object):
+            def test_from_model(self, obj):
+                return "nothing"
+            test_from_model.short_description = "not really the model"
+        self.assertEquals(
+            label_for_field("test_from_model", Article, model_admin=MockModelAdmin),
+            "not really the model"
+        )
+        self.assertEquals(
+            label_for_field("test_from_model", Article,
+                model_admin = MockModelAdmin,
+                return_attr = True
+            ),
+            ("not really the model", MockModelAdmin.test_from_model)
+        )