- break out the concept of "down revision" into two pieces:

down_revision and "dependencies".  For migration traversal, the downrevs
we care about are the union of these two sets.  however for location of nodes
and branch labeling, we look only at down_revsion.  this works really well
and allows us to have mutually-dependent trees that can easily be itererated
independently of each other.  docs are needed

1 files changed, 11 insertions, 11 deletions

diff --git a/alembic/migration.py b/alembic/migration.py
index 7d854ba..eefb1d1 100644
--- a/alembic/migration.py
+++ b/alembic/migration.py
@@ -553,7 +553,7 @@ class RevisionStep(MigrationStep):
     @property
     def from_revisions(self):
         if self.is_upgrade:
-            return self.revision._down_revision_tuple
+            return self.revision._all_down_revisions
         else:
             return (self.revision.revision, )
 
@@ -562,11 +562,11 @@ class RevisionStep(MigrationStep):
         if self.is_upgrade:
             return (self.revision.revision, )
         else:
-            return self.revision._down_revision_tuple
+            return self.revision._all_down_revisions
 
     @property
     def _has_scalar_down_revision(self):
-        return len(self.revision._down_revision_tuple) == 1
+        return len(self.revision._all_down_revisions) == 1
 
     def should_delete_branch(self, heads):
         if not self.is_downgrade:
@@ -575,7 +575,7 @@ class RevisionStep(MigrationStep):
         if self.revision.revision not in heads:
             return False
 
-        downrevs = self.revision._down_revision_tuple
+        downrevs = self.revision._all_down_revisions
         if not downrevs:
             # is a base
             return True
@@ -587,7 +587,7 @@ class RevisionStep(MigrationStep):
 
             descendants = set(
                 r.revision for r in self.revision_map._get_descendant_nodes(
-                    self.revision_map.get_revisions(downrev.nextrev),
+                    self.revision_map.get_revisions(downrev._all_nextrev),
                     check=False
                 )
             )
@@ -606,7 +606,7 @@ class RevisionStep(MigrationStep):
 
             # TODO: this doesn't work; make sure tests are here to ensure
             # this fails
-            #if len(downrev.nextrev.intersection(heads).difference(
+            #if len(downrev._all_nextrev.intersection(heads).difference(
             #        [self.revision.revision])):
 
                 return True
@@ -662,7 +662,7 @@ class RevisionStep(MigrationStep):
         if not self.is_upgrade:
             return False
 
-        downrevs = self.revision._down_revision_tuple
+        downrevs = self.revision._all_down_revisions
 
         if not downrevs:
             # is a base
@@ -680,7 +680,7 @@ class RevisionStep(MigrationStep):
         if not self.is_upgrade:
             return False
 
-        downrevs = self.revision._down_revision_tuple
+        downrevs = self.revision._all_down_revisions
 
         if len(downrevs) > 1 and \
                 len(heads.intersection(downrevs)) > 1:
@@ -692,7 +692,7 @@ class RevisionStep(MigrationStep):
         if not self.is_downgrade:
             return False
 
-        downrevs = self.revision._down_revision_tuple
+        downrevs = self.revision._all_down_revisions
 
         if self.revision.revision in heads and len(downrevs) > 1:
             return True
@@ -701,12 +701,12 @@ class RevisionStep(MigrationStep):
 
     def update_version_num(self, heads):
         if not self._has_scalar_down_revision:
-            downrev = heads.intersection(self.revision._down_revision_tuple)
+            downrev = heads.intersection(self.revision._all_down_revisions)
             assert len(downrev) == 1, \
                 "Can't do an UPDATE because downrevision is ambiguous"
             down_revision = list(downrev)[0]
         else:
-            down_revision = self.revision.down_revision
+            down_revision = self.revision._all_down_revisions[0]
 
         if self.is_upgrade:
             return down_revision, self.revision.revision