Fixed #1662 -- Added resolver for string-form model references for models that have already been loaded, with tests to validate both forward and backward referenced model names. Light refactoring of model loading to make regression tests behave more like normal model loading. Also clarifies the text of some validation errors.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@3195 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/core/management.py

@@ -855,7 +855,7 @@ def get_validation_errors(outfile, app=None):
             if f.rel:
                 rel_opts = f.rel.to._meta
                 if f.rel.to not in models.get_models():
-                    e.add(opts, "'%s' has relation with uninstalled model %s" % (f.name, rel_opts.object_name))
+                    e.add(opts, "'%s' has relation with model %s, which has not been installed" % (f.name, rel_opts.object_name))
 
                 rel_name = RelatedObject(f.rel.to, cls, f).get_accessor_name()
                 for r in rel_opts.fields:
@@ -876,7 +876,7 @@ def get_validation_errors(outfile, app=None):
             # existing fields, m2m fields, m2m related objects or related objects
             rel_opts = f.rel.to._meta
             if f.rel.to not in models.get_models():
-                e.add(opts, "'%s' has m2m relation with uninstalled model %s" % (f.name, rel_opts.object_name))
+                e.add(opts, "'%s' has m2m relation with model %s, which has not been installed" % (f.name, rel_opts.object_name))
 
             rel_name = RelatedObject(f.rel.to, cls, f).get_accessor_name()
             for r in rel_opts.fields:

django/db/models/fields/related.py

@@ -1,5 +1,5 @@
 from django.db import backend, connection, transaction
-from django.db.models import signals
+from django.db.models import signals, get_model
 from django.db.models.fields import AutoField, Field, IntegerField, get_ul_class
 from django.db.models.related import RelatedObject
 from django.utils.translation import gettext_lazy, string_concat
@@ -23,6 +23,11 @@ def add_lookup(rel_cls, field):
     name = field.rel.to
     module = rel_cls.__module__
     key = (module, name)
+    model = get_model(rel_cls._meta.app_label,field.rel.to)
+    if model:
+        field.rel.to = model
+        field.do_related_class(model, rel_cls)
+    else:
         pending_lookups.setdefault(key, []).append((rel_cls, field))
 
 def do_pending_lookups(sender):

django/db/models/loading.py

@@ -5,36 +5,45 @@ from django.core.exceptions import ImproperlyConfigured
 
 __all__ = ('get_apps', 'get_app', 'get_models', 'get_model', 'register_models')
 
-_app_list = None # Cache of installed apps.
+_app_list = []   # Cache of installed apps.
+                 # Entry is not placed in app_list cache until entire app is loaded.
 _app_models = {} # Dictionary of models against app label
                  # Each value is a dictionary of model name: model class
+                 # Applabel and Model entry exists in cache when individual model is loaded.
+_loaded = False  # Has the contents of settings.INSTALLED_APPS been loaded? 
+                 # i.e., has get_apps() been called?
 
 def get_apps():
     "Returns a list of all installed modules that contain models."
     global _app_list
-    if _app_list is not None:
+    global _loaded
-        return _app_list
+    if not _loaded:
-    _app_list = []
+        _loaded = True
         for app_name in settings.INSTALLED_APPS:
             try:
-            mod = __import__(app_name, '', '', ['models'])
+                load_app(app_name)
             except ImportError:
                 pass # Assume this app doesn't have a models.py in it.
                      # GOTCHA: It may have a models.py that raises ImportError.
-        else:
-            try:
-                _app_list.append(mod.models)
             except AttributeError:
                 pass # This app doesn't have a models.py in it.
     return _app_list
 
 def get_app(app_label):
     "Returns the module containing the models for the given app_label."
+    get_apps() # Run get_apps() to populate the _app_list cache. Slightly hackish.
     for app_name in settings.INSTALLED_APPS:
         if app_label == app_name.split('.')[-1]:
-            return __import__(app_name, '', '', ['models']).models
+            return load_app(app_name)
     raise ImproperlyConfigured, "App with label %s could not be found" % app_label
 
+def load_app(app_name):
+    "Loads the app with the provided fully qualified name, and returns the model module."
+    mod = __import__(app_name, '', '', ['models'])
+    if mod.models not in _app_list:
+        _app_list.append(mod.models)
+    return mod.models
+    
 def get_models(app_mod=None):
     """
     Given a module containing models, returns a list of the models. Otherwise

tests/regressiontests/string_lookup/models.py

@@ -0,0 +1,48 @@
+from django.db import models
+
+class Foo(models.Model):
+    name = models.CharField(maxlength=50)
+
+    def __str__(self):
+        return "Foo %s" % self.name
+
+class Bar(models.Model):
+    name = models.CharField(maxlength=50)
+    normal = models.ForeignKey(Foo, related_name='normal_foo')
+    fwd = models.ForeignKey("Whiz")
+    back = models.ForeignKey("Foo")
+
+    def __str__(self):
+        return "Bar %s" % self.place.name
+
+class Whiz(models.Model):
+    name = models.CharField(maxlength = 50)
+
+    def __str__(self):
+        return "Whiz %s" % self.name
+
+API_TESTS = """
+# Regression test for #1662: Check that string form referencing of models works, both as
+# pre and post reference
+
+>>> f1 = Foo(name="Foo1")
+>>> f1.save()
+>>> f2 = Foo(name="Foo1")
+>>> f2.save()
+
+>>> w1 = Whiz(name="Whiz1")
+>>> w1.save()
+
+>>> b1 = Bar(name="Bar1", normal=f1, fwd=w1, back=f2)
+>>> b1.save()
+
+>>> b1.normal
+<Foo: Foo Foo1>
+
+>>> b1.fwd
+<Whiz: Whiz Whiz1>
+
+>>> b1.back
+<Foo: Foo Foo1>
+
+"""

tests/runtests.py

@@ -162,10 +162,11 @@ class TestRunner:
         # Initialize the test database.
         cursor = connection.cursor()
 
+        from django.db.models.loading import load_app
         # Install the core always installed apps
         for app in ALWAYS_INSTALLED_APPS:
             self.output(1, "Installing contrib app %s" % app)
-            mod = __import__(app + ".models", '', '', [''])
+            mod = load_app(app)
             management.install(mod)
 
         # Run the tests for each test model.
@@ -173,8 +174,7 @@ class TestRunner:
         for model_dir, model_name in test_models:
             self.output(1, "%s model: Importing" % model_name)
             try:
-                # TODO: Abstract this into a meta.get_app() replacement?
+                mod = load_app(model_dir + '.' + model_name)
-                mod = __import__(model_dir + '.' + model_name + '.models', '', '', [''])
             except Exception, e:
                 log_error(model_name, "Error while importing", ''.join(traceback.format_exception(*sys.exc_info())[1:]))
                 continue