Fix issue with string args in GenericRelation.

Fixes sphinx-doc#42.

The tests intended to capture the issue but actually
don't trigger the real issue in the test scenario,
so they may not be appropriate. I tried making
a 2nd app to see if the deferred issue would show
up but it does not.

sphinxcontrib_django/docstrings/field_utils.py

@@ -78,10 +78,14 @@ def get_field_verbose_name(field):
             related_name = (
                 related_name or field.remote_field.model._meta.verbose_name_plural
             )
-            # If field is a foreign key or a ManyToMany field, use the prefix "All"
-            verbose_name = (
-                f"All {related_name} of this {field.model._meta.verbose_name}"
+            # handle potential str-type deferred model names
+            forward_name = (
+                field.model
+                if isinstance(field.model, str)
+                else field.model._meta.verbose_name
             )
+            # If field is a foreign key or a ManyToMany field, use the prefix "All"
+            verbose_name = f"All {related_name} of this {forward_name}"
         # Link to the origin of the reverse related field if it's not from an abstract model
         if not field.remote_field.model._meta.abstract:
             verbose_name += (

tests/roots/test-docstrings/dummy_django_app/settings.py

@@ -9,6 +9,7 @@
     "django.contrib.auth",
     "django.contrib.contenttypes",
     "dummy_django_app",
+    "dummy_django_app2",
 ]
 
 USE_TZ = False

tests/roots/test-docstrings/dummy_django_app2/models.py

@@ -0,0 +1,7 @@
+from django.contrib.contenttypes.fields import GenericRelation
+from django.db import models
+
+
+class GenericRelationModel(models.Model):
+    # specifically test deferred string-type argument
+    relation_field = GenericRelation("dummy_django_app.TaggedItem")

tests/test_attribute_docstrings.py

@@ -447,3 +447,28 @@ def test_phonenumber_field(app, do_autodoc):
             "   Phone number",
             "",
         ]
+
+
+@pytest.mark.sphinx("html", testroot="docstrings")
+def test_generic_relation_field(app, do_autodoc):
+    actual = do_autodoc(
+        app, "attribute", "dummy_django_app2.models.GenericRelationModel.relation_field"
+    )
+    print(actual)
+    assert list(actual) == [
+        "",
+        ".. py:attribute:: GenericRelationModel.relation_field",
+        "   :module: dummy_django_app2.models",
+        "",
+        (
+            "   Type: Reverse"
+            " :class:`~django.contrib.contenttypes.fields.GenericRelation` from"
+            " :class:`~dummy_django_app2.models.GenericRelationModel`"
+        ),
+        "",
+        (
+            "   All + of this tagged item (related name of"
+            " :attr:`~dummy_django_app2.models.GenericRelationModel.relation_field`)"
+        ),
+        "",
+    ]

tests/test_class_docstrings.py

@@ -367,3 +367,30 @@ def test_form(app, do_autodoc):
         "   * ``test2``: Test2 (:class:`~django.forms.CharField`)",
         "",
     ]
+
+
+@pytest.mark.sphinx("html", testroot="docstrings")
+def test_relation_model(app, do_autodoc):
+    actual = do_autodoc(app, "class", "dummy_django_app2.models.GenericRelationModel")
+    print(actual)
+    assert list(actual) == [
+        "",
+        ".. py:class:: GenericRelationModel(id)",
+        "   :module: dummy_django_app2.models",
+        "",
+        "   :param id: Primary key: ID",
+        "   :type id: ~django.db.models.AutoField",
+        "",
+        "   Relationship fields:",
+        "",
+        (
+            "   :param relation_field: Relation field (related name:"
+            " :attr:`~dummy_django_app.models.TaggedItem.+`)"
+        ),
+        (
+            "   :type relation_field:"
+            " :class:`~django.contrib.contenttypes.fields.GenericRelation` to"
+            " :class:`~dummy_django_app.models.TaggedItem`"
+        ),
+        "",
+    ]

tests/test_data_docstrings.py

@@ -17,16 +17,16 @@ def test_data(app, do_autodoc):
         "   :module: dummy_django_app.settings",
         (
             "   :value: ['django.contrib.auth', 'django.contrib.contenttypes',"
-            " 'dummy_django_app']"
+            " 'dummy_django_app', 'dummy_django_app2']"
         ),
         "",
         "   These are the installed apps",
         "",
         "   .. code-block:: JavaScript",
         "",
         (
-            "       ['django.contrib.auth', 'django.contrib.contenttypes',"
-            " 'dummy_django_app']\n"
+            "       [\n    'django.contrib.auth',\n    'django.contrib.contenttypes',\n"
+            "    'dummy_django_app',\n    'dummy_django_app2',\n]\n"
         ),
         "",
     ]