Fixes #2653 -- Modified related field utility methods to return None as the related name for symmetrical m2m fields on self. Updated validators and unit tests to account for the new behavior.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@3734 bcc190cf-cafb-0310-a4f2-bffc1f526a37

3 files changed, 59 insertions, 24 deletions

diff --git a/django/core/management.py b/django/core/management.py
index 799ec30d2c..3dd9666eb5 100644
--- a/django/core/management.py
+++ b/django/core/management.py
@@ -903,27 +903,32 @@ def get_validation_errors(outfile, app=None):
 
             rel_name = RelatedObject(f.rel.to, cls, f).get_accessor_name()
             rel_query_name = f.related_query_name()
-            for r in rel_opts.fields:
-                if r.name == rel_name:
-                    e.add(opts, "Accessor for m2m field '%s' clashes with field '%s.%s'. Add a related_name argument to the definition for '%s'." % (f.name, rel_opts.object_name, r.name, f.name))
-                if r.name == rel_query_name:
-                    e.add(opts, "Reverse query name for m2m field '%s' clashes with field '%s.%s'. Add a related_name argument to the definition for '%s'." % (f.name, rel_opts.object_name, r.name, f.name))
-            for r in rel_opts.many_to_many:
-                if r.name == rel_name:
-                    e.add(opts, "Accessor for m2m field '%s' clashes with m2m field '%s.%s'. Add a related_name argument to the definition for '%s'." % (f.name, rel_opts.object_name, r.name, f.name))
-                if r.name == rel_query_name:
-                    e.add(opts, "Reverse query name for m2m field '%s' clashes with m2m field '%s.%s'. Add a related_name argument to the definition for '%s'." % (f.name, rel_opts.object_name, r.name, f.name))
-            for r in rel_opts.get_all_related_many_to_many_objects():
-                if r.field is not f:
+            # If rel_name is none, there is no reverse accessor.
+            # (This only occurs for symmetrical m2m relations to self). 
+            # If this is the case, there are no clashes to check for this field, as
+            # there are no reverse descriptors for this field.
+            if rel_name is not None:
+                for r in rel_opts.fields:
+                    if r.name == rel_name:
+                        e.add(opts, "Accessor for m2m field '%s' clashes with field '%s.%s'. Add a related_name argument to the definition for '%s'." % (f.name, rel_opts.object_name, r.name, f.name))
+                    if r.name == rel_query_name:
+                        e.add(opts, "Reverse query name for m2m field '%s' clashes with field '%s.%s'. Add a related_name argument to the definition for '%s'." % (f.name, rel_opts.object_name, r.name, f.name))
+                for r in rel_opts.many_to_many:
+                    if r.name == rel_name:
+                        e.add(opts, "Accessor for m2m field '%s' clashes with m2m field '%s.%s'. Add a related_name argument to the definition for '%s'." % (f.name, rel_opts.object_name, r.name, f.name))
+                    if r.name == rel_query_name:
+                        e.add(opts, "Reverse query name for m2m field '%s' clashes with m2m field '%s.%s'. Add a related_name argument to the definition for '%s'." % (f.name, rel_opts.object_name, r.name, f.name))
+                for r in rel_opts.get_all_related_many_to_many_objects():
+                    if r.field is not f:
+                        if r.get_accessor_name() == rel_name:
+                            e.add(opts, "Accessor for m2m field '%s' clashes with related m2m field '%s.%s'. Add a related_name argument to the definition for '%s'." % (f.name, rel_opts.object_name, r.get_accessor_name(), f.name))
+                        if r.get_accessor_name() == rel_query_name:
+                            e.add(opts, "Reverse query name for m2m field '%s' clashes with related m2m field '%s.%s'. Add a related_name argument to the definition for '%s'." % (f.name, rel_opts.object_name, r.get_accessor_name(), f.name))
+                for r in rel_opts.get_all_related_objects():
                     if r.get_accessor_name() == rel_name:
-                        e.add(opts, "Accessor for m2m field '%s' clashes with related m2m field '%s.%s'. Add a related_name argument to the definition for '%s'." % (f.name, rel_opts.object_name, r.get_accessor_name(), f.name))
+                        e.add(opts, "Accessor for m2m field '%s' clashes with related field '%s.%s'. Add a related_name argument to the definition for '%s'." % (f.name, rel_opts.object_name, r.get_accessor_name(), f.name))
                     if r.get_accessor_name() == rel_query_name:
-                        e.add(opts, "Reverse query name for m2m field '%s' clashes with related m2m field '%s.%s'. Add a related_name argument to the definition for '%s'." % (f.name, rel_opts.object_name, r.get_accessor_name(), f.name))
-            for r in rel_opts.get_all_related_objects():
-                if r.get_accessor_name() == rel_name:
-                    e.add(opts, "Accessor for m2m field '%s' clashes with related field '%s.%s'. Add a related_name argument to the definition for '%s'." % (f.name, rel_opts.object_name, r.get_accessor_name(), f.name))
-                if r.get_accessor_name() == rel_query_name:
-                    e.add(opts, "Reverse query name for m2m field '%s' clashes with related field '%s.%s'. Add a related_name argument to the definition for '%s'." % (f.name, rel_opts.object_name, r.get_accessor_name(), f.name))
+                        e.add(opts, "Reverse query name for m2m field '%s' clashes with related field '%s.%s'. Add a related_name argument to the definition for '%s'." % (f.name, rel_opts.object_name, r.get_accessor_name(), f.name))
 
         # Check admin attribute.
         if opts.admin is not None:
diff --git a/django/db/models/related.py b/django/db/models/related.py
index ee3b916cf4..ac1ec50ca2 100644
--- a/django/db/models/related.py
+++ b/django/db/models/related.py
@@ -131,6 +131,9 @@ class RelatedObject(object):
         # many-to-many objects. It uses the lower-cased object_name + "_set",
         # but this can be overridden with the "related_name" option.
         if self.field.rel.multiple:
+            # If this is a symmetrical m2m relation on self, there is no reverse accessor.
+            if getattr(self.field.rel, 'symmetrical', False) and self.model == self.parent_model:
+                return None
             return self.field.rel.related_name or (self.opts.object_name.lower() + '_set')
         else:
             return self.field.rel.related_name or (self.opts.object_name.lower())
diff --git a/tests/modeltests/invalid_models/models.py b/tests/modeltests/invalid_models/models.py
index 5540c1bd5f..2299cd85e6 100644
--- a/tests/modeltests/invalid_models/models.py
+++ b/tests/modeltests/invalid_models/models.py
@@ -68,15 +68,34 @@ class SelfClashForeign(models.Model):
     foreign_1 = models.ForeignKey("SelfClashForeign", related_name='id')
     foreign_2 = models.ForeignKey("SelfClashForeign", related_name='src_safe')
 
+class ValidM2M(models.Model):
+    src_safe = models.CharField(maxlength=10)
+    validm2m = models.CharField(maxlength=10)
+
+    # M2M fields are symmetrical by default. Symmetrical M2M fields
+    # on self don't require a related accessor, so many potential
+    # clashes are avoided.
+    validm2m_set = models.ManyToManyField("ValidM2M")
+    
+    m2m_1 = models.ManyToManyField("ValidM2M", related_name='id')
+    m2m_2 = models.ManyToManyField("ValidM2M", related_name='src_safe')
+
+    m2m_3 = models.ManyToManyField('self')
+    m2m_4 = models.ManyToManyField('self')
+
 class SelfClashM2M(models.Model):
     src_safe = models.CharField(maxlength=10)
     selfclashm2m = models.CharField(maxlength=10)
 
-    selfclashm2m_set = models.ManyToManyField("SelfClashM2M")
-    m2m_1 = models.ManyToManyField("SelfClashM2M", related_name='id')
-    m2m_2 = models.ManyToManyField("SelfClashM2M", related_name='src_safe')
-
+    # Non-symmetrical M2M fields _do_ have related accessors, so 
+    # there is potential for clashes.
+    selfclashm2m_set = models.ManyToManyField("SelfClashM2M", symmetrical=False)
+    
+    m2m_1 = models.ManyToManyField("SelfClashM2M", related_name='id', symmetrical=False)
+    m2m_2 = models.ManyToManyField("SelfClashM2M", related_name='src_safe', symmetrical=False)
 
+    m2m_3 = models.ManyToManyField('self', symmetrical=False)
+    m2m_4 = models.ManyToManyField('self', symmetrical=False)
 
 model_errors = """invalid_models.fielderrors: "charfield": CharFields require a "maxlength" attribute.
 invalid_models.fielderrors: "floatfield": FloatFields require a "decimal_places" attribute.
@@ -147,9 +166,17 @@ invalid_models.selfclashforeign: Accessor for field 'foreign_2' clashes with fie
 invalid_models.selfclashforeign: Reverse query name for field 'foreign_2' clashes with field 'SelfClashForeign.src_safe'. Add a related_name argument to the definition for 'foreign_2'.
 invalid_models.selfclashm2m: Accessor for m2m field 'selfclashm2m_set' clashes with m2m field 'SelfClashM2M.selfclashm2m_set'. Add a related_name argument to the definition for 'selfclashm2m_set'.
 invalid_models.selfclashm2m: Reverse query name for m2m field 'selfclashm2m_set' clashes with field 'SelfClashM2M.selfclashm2m'. Add a related_name argument to the definition for 'selfclashm2m_set'.
+invalid_models.selfclashm2m: Accessor for m2m field 'selfclashm2m_set' clashes with related m2m field 'SelfClashM2M.selfclashm2m_set'. Add a related_name argument to the definition for 'selfclashm2m_set'.
 invalid_models.selfclashm2m: Accessor for m2m field 'm2m_1' clashes with field 'SelfClashM2M.id'. Add a related_name argument to the definition for 'm2m_1'.
 invalid_models.selfclashm2m: Accessor for m2m field 'm2m_2' clashes with field 'SelfClashM2M.src_safe'. Add a related_name argument to the definition for 'm2m_2'.
 invalid_models.selfclashm2m: Reverse query name for m2m field 'm2m_1' clashes with field 'SelfClashM2M.id'. Add a related_name argument to the definition for 'm2m_1'.
 invalid_models.selfclashm2m: Reverse query name for m2m field 'm2m_2' clashes with field 'SelfClashM2M.src_safe'. Add a related_name argument to the definition for 'm2m_2'.
+invalid_models.selfclashm2m: Accessor for m2m field 'm2m_3' clashes with m2m field 'SelfClashM2M.selfclashm2m_set'. Add a related_name argument to the definition for 'm2m_3'.
+invalid_models.selfclashm2m: Accessor for m2m field 'm2m_3' clashes with related m2m field 'SelfClashM2M.selfclashm2m_set'. Add a related_name argument to the definition for 'm2m_3'.
+invalid_models.selfclashm2m: Accessor for m2m field 'm2m_3' clashes with related m2m field 'SelfClashM2M.selfclashm2m_set'. Add a related_name argument to the definition for 'm2m_3'.
+invalid_models.selfclashm2m: Accessor for m2m field 'm2m_4' clashes with m2m field 'SelfClashM2M.selfclashm2m_set'. Add a related_name argument to the definition for 'm2m_4'.
+invalid_models.selfclashm2m: Accessor for m2m field 'm2m_4' clashes with related m2m field 'SelfClashM2M.selfclashm2m_set'. Add a related_name argument to the definition for 'm2m_4'.
+invalid_models.selfclashm2m: Accessor for m2m field 'm2m_4' clashes with related m2m field 'SelfClashM2M.selfclashm2m_set'. Add a related_name argument to the definition for 'm2m_4'.
+invalid_models.selfclashm2m: Reverse query name for m2m field 'm2m_3' clashes with field 'SelfClashM2M.selfclashm2m'. Add a related_name argument to the definition for 'm2m_3'.
+invalid_models.selfclashm2m: Reverse query name for m2m field 'm2m_4' clashes with field 'SelfClashM2M.selfclashm2m'. Add a related_name argument to the definition for 'm2m_4'.
 """
-