adding code to support diffs between versions out of the box. additio…

…nally objects now have a FIELD_revision attribute if they contain content from an old revision

git-svn-id: https://django-rcsfield.googlecode.com/svn/trunk@51 d91cc5cc-1343-0410-b1ed-e1360c4e4ba3

rcsfield/backends/bzr.py

@@ -140,7 +140,23 @@ def move(self, key_from, key_to):
             return True
         except:
             return False
+
 
+    def diff(self, key1, rev1, key2, rev2):
+        """
+        Returns a textual unified diff of two entities at specified revisions.
+        Takes two parameters for keyname to support diffing renamed files.
+        
+        """
+        import difflib
+        c1 = self.fetch(key1, rev1)
+        c2 = self.fetch(key2, rev2)
+        diff = difflib.unified_diff(c1.splitlines(1),
+                                    c2.splitlines(1),
+                                    'Revision: %s' % rev1, 
+                                    'Revision: %s' % rev2
+                                    )
+        return diff
 
 
 
@@ -152,7 +168,8 @@ def move(self, key_from, key_to):
 initial = rcs.initial
 get_revisions = rcs.get_revisions
 move = rcs.move
+diff = rcs.diff
 
-__all__ = ('fetch', 'commit', 'initial', 'get_revisions', 'move')
+__all__ = ('fetch', 'commit', 'initial', 'get_revisions', 'move', 'diff')
 
 

rcsfield/fields.py

@@ -90,11 +90,63 @@ def get_FIELD_revisions(self, instance, field):
                                                            field.attname, 
                                                            instance.id))
 
+
+    def get_FIELD_diff(self, instance, rev1, rev2=None, field=None):
+        """
+        Returns a generator which yields lines of a textual diff between
+        two revisions.
+        Supports two operation modes:
+        
+           ObjectA.get_field_diff(3): returns a diff between the contents of
+           the field ``field`` at revision 3 against revision of ObjectA.
+           Direction is ---3 / +++ObjectA
+           
+           ObjectA.get_field_diff(3,7): returns a diff between the contents of
+           the field ``field`` at revision 7 against revision 3..
+           Direction is ---3/+++7
+           
+        """
+
+
+        if rev2 is None:
+            rev2 = getattr(instance, '%s_revision' % field.attname, 'head')
+
+        if rev1 == rev2: #do not attempt to diff identical content for performance reasons
+            return ""
+
+        if rev2 == 'head':
+            import difflib
+            old = backend.fetch(self.rcskey_format % (instance._meta.app_label,
+                                                      instance.__class__.__name__,
+                                                      field.attname,
+                                                      instance.id),
+                                rev1,
+                               )
+            diff = difflib.unified_diff(old.splitlines(1),
+                                       getattr(instance, field.attname).splitlines(1),
+                                       'Revision: %s' % rev1, 
+                                       'Revision: %s' % getattr(instance, "%s_revision" % field.attname, 'head'),
+                                       )
+            return diff
+
+        else: #diff two arbitrary revisions
+            return backend.diff(self.rcskey_format % (instance._meta.app_label,
+                                                      instance.__class__.__name__,
+                                                      field.attname,
+                                                      instance.id),
+                                rev1,
+                                self.rcskey_format % (instance._meta.app_label,
+                                                      instance.__class__.__name__,
+                                                      field.attname,
+                                                      instance.id),
+                                rev2,
+                               )
 
     def contribute_to_class(self, cls, name):
         super(RcsTextField, self).contribute_to_class(cls, name)
         setattr(cls, 'get_%s_revisions' % self.name, curry(self.get_FIELD_revisions, field=self))
         setattr(cls, 'get_changed_revisions', curry(self.get_changed_revisions, field=self))
+        setattr(cls, 'get_%s_diff' % self.name, curry(self.get_FIELD_diff, field=self))
         dispatcher.connect(self.post_save, signal=signals.post_save, sender=cls)
 
 

rcsfield/manager.py

@@ -34,6 +34,7 @@ def iterator(self):
                     try:
                         olddata = backend.fetch(file_path, self._rev)
                         setattr(obj, field.attname, olddata)
+                        setattr(obj, '%s_revision' % field.attname, self._rev)
                     except:
                         # for now just ignore errors raised in the backend 
                         # and return the content from the db (aka head revision)