[2.2.x] Fixed #30280 -- Restored Model.get_FIELD_display()'s coercion of lazy strings.

Reverted cc79c7ee.

Backport of ea071870 from master.

django/db/models/base.py

@@ -28,6 +28,7 @@ from django.db.models.signals import (
     class_prepared, post_init, post_save, pre_init, pre_save,
 )
 from django.db.models.utils import make_model_tuple
+from django.utils.encoding import force_str
 from django.utils.text import capfirst, get_text_list
 from django.utils.translation import gettext_lazy as _
 from django.utils.version import get_version
@@ -921,7 +922,8 @@ class Model(metaclass=ModelBase):
 
     def _get_FIELD_display(self, field):
         value = getattr(self, field.attname)
-        return dict(field.flatchoices).get(value, value)
+        # force_str() to coerce lazy strings.
+        return force_str(dict(field.flatchoices).get(value, value), strings_only=True)
 
     def _get_next_or_previous_by_FIELD(self, field, is_next, **kwargs):
         if not self.pk:

tests/choices/models.py

@@ -10,12 +10,13 @@ field. This method returns the "human-readable" value of the field.
 """
 
 from django.db import models
+from django.utils.translation import gettext_lazy as _
 
 
 class Person(models.Model):
     GENDER_CHOICES = (
-        ('M', 'Male'),
-        ('F', 'Female'),
+        ('M', _('Male')),
+        ('F', _('Female')),
     )
     name = models.CharField(max_length=20)
     gender = models.CharField(max_length=1, choices=GENDER_CHOICES)

tests/choices/tests.py

@@ -20,3 +20,6 @@ class ChoicesTests(TestCase):
 
         a.gender = 'U'
         self.assertEqual(a.get_gender_display(), 'U')
+
+        # _get_FIELD_display() coerces lazy strings.
+        self.assertIsInstance(a.get_gender_display(), str)