3 files changed, 37 insertions, 4 deletions

diff --git a/source/blender/blenkernel/BKE_idprop.h b/source/blender/blenkernel/BKE_idprop.h
index d61d274dd36..09083364fd9 100644
--- a/source/blender/blenkernel/BKE_idprop.h
+++ b/source/blender/blenkernel/BKE_idprop.h
@@ -48,7 +48,22 @@ void IDP_LinkID(struct IDProperty *prop, ID *id);
 void IDP_UnlinkID(struct IDProperty *prop);
 
 /*-------- Group Functions -------*/
-void IDP_AddToGroup(struct IDProperty *group, struct IDProperty *prop);
+/*
+This function has a sanity check to make sure ID properties with the same name don't
+get added to the group.
+
+The sanity check just means the property is not added to the group if another property
+exists with the same name; the client code using ID properties then needs to detect this 
+(the function that adds new properties to groups, IDP_AddToGroup, returns 0 if a property can't
+be added to the group, and 1 if it can) and free the property.
+
+Currently the code to free ID properties is designesd to leave the actual struct
+you pass it un-freed, this is needed for how the system works.  This means
+to free an ID property, you first call IDP_FreeProperty then MEM_freeN the
+struct.  In the future this will just be IDP_FreeProperty and the code will
+be reorganized to work properly.
+*/
+int IDP_AddToGroup(struct IDProperty *group, struct IDProperty *prop);
 void IDP_RemFromGroup(struct IDProperty *group, struct IDProperty *prop);
 IDProperty *IDP_GetPropertyFromGroup(struct IDProperty *prop, char *name);
 
diff --git a/source/blender/blenkernel/intern/idprop.c b/source/blender/blenkernel/intern/idprop.c
index 66feaffadb7..6a748a295b9 100644
--- a/source/blender/blenkernel/intern/idprop.c
+++ b/source/blender/blenkernel/intern/idprop.c
@@ -14,6 +14,8 @@
 #include <stdlib.h>
 #include <string.h>
 
+#define BSTR_EQ(a, b)	(*(a) == *(b) && !strcmp(a, b))
+
 /* IDPropertyTemplate is a union in DNA_ID.h */
 static char idp_size_table[] = {
 	0, /*strings don't have fixed sizes :)*/
@@ -135,10 +137,19 @@ void IDP_UnlinkID(IDProperty *prop)
 }
 
 /*-------- Group Functions -------*/
-void IDP_AddToGroup(IDProperty *group, IDProperty *prop)
+/*returns 0 if an id property with the same name exists and it failed,
+  or 1 if it succeeded in adding to the group.*/
+int IDP_AddToGroup(IDProperty *group, IDProperty *prop)
 {
+	IDProperty *loop;
+	for (loop=group->data.group.first; loop; loop=loop->next) {
+		if (BSTR_EQ(loop->name, prop->name)) return 0;
+	}
+
 	group->len++;
 	BLI_addtail(&group->data.group, prop);
+
+	return 1;
 }
 
 void IDP_RemFromGroup(IDProperty *group, IDProperty *prop)
diff --git a/source/blender/python/api2_2x/IDProp.c b/source/blender/python/api2_2x/IDProp.c
index 06a8d75b549..ff785c4d93d 100644
--- a/source/blender/python/api2_2x/IDProp.c
+++ b/source/blender/python/api2_2x/IDProp.c
@@ -264,7 +264,11 @@ char *BPy_IDProperty_Map_ValidateAndCreate(char *name, IDProperty *group, PyObje
 		Py_XDECREF(vals);
 	}
 	
-	IDP_AddToGroup(group, prop);
+	if (!IDP_AddToGroup(group, prop)) {
+		IDP_FreeProperty(prop);
+		MEM_freeN(prop);
+		return "property name already exists in group";
+	}
 	return NULL;
 }
 
@@ -848,7 +852,10 @@ PyObject *BPy_IDGroup_NewProperty(BPy_IDProperty *self, PyObject *args)
 				"invalid id property type");
 	}
 
-	IDP_AddToGroup(self->prop, prop);
+	if (!IDP_AddToGroup(self->prop, prop)) {
+		return EXPP_ReturnPyObjError( PyExc_RuntimeError,
+				"property name already exists in group");
+	}
 	pyprop = BPy_Wrap_IDProperty(self->id, prop);
 	//Py_XINCREF(pyprop);
 	return pyprop;