Move empty downgrade revisions check to make it specific to branch filtering case...

Fixed regression in new versioning traversal where "alembic downgrade head" (or equivalent) fails instead of iterating no revisions.

Fixes: #839
Change-Id: I9e8463ee067761ee4588c2ccc1b1009e2be97c38

diff --git a/alembic/script/revision.py b/alembic/script/revision.py
index 7fbd670a89c3da1b92e49713d2d2e1c73faa0e02..ef03d2e54ab2c6f9ab0f17b72be2e6bd050ba478 100644 (file)
--- a/alembic/script/revision.py
+++ b/alembic/script/revision.py
@@ -1206,11 +1206,11 @@ class RevisionMap(object):
                 )
             )
 
-        # Ensure we didn't throw everything away.
-        if len(roots) == 0:
-            raise RevisionError(
-                "Not a valid downgrade target from current heads"
-            )
+            # Ensure we didn't throw everything away when filtering branches.
+            if len(roots) == 0:
+                raise RevisionError(
+                    "Not a valid downgrade target from current heads"
+                )
 
         heads = self.get_revisions(upper)
 

diff --git a/docs/build/unreleased/839.rst b/docs/build/unreleased/839.rst
new file mode 100644 (file)
index 0000000..85b0a48
--- /dev/null
+++ b/docs/build/unreleased/839.rst
@@ -0,0 +1,6 @@
+.. change::
+    :tags: bug, versioning, regression
+    :tickets: 839
+
+    Fixed regression in new versioning traversal where "alembic downgrade head"
+    (or equivalent) fails instead of iterating no revisions.

diff --git a/tests/test_version_traversal.py b/tests/test_version_traversal.py
index f224731f0fa9ddfd859e6fdd7c1e7847d3c31d69..bdc7f658bd4f5ddcf3bbf9e2811f5bd3c2ecf2b6 100644 (file)
--- a/tests/test_version_traversal.py
+++ b/tests/test_version_traversal.py
@@ -58,6 +58,11 @@ class RevisionPathTest(MigrationTest):
             self.a.revision, [self.a.revision], [], {self.a.revision}
         )
 
+    def test_downgrade_to_existing_head(self):
+        self._assert_downgrade(
+            self.e.revision, [self.e.revision], [], {self.e.revision}
+        )
+
     def test_upgrade_path(self):
         self._assert_upgrade(
             self.e.revision,
@@ -511,15 +516,6 @@ class BranchedPathTest(MigrationTest):
             [self.c1.revision, self.c2.revision],
         )
 
-    def test_not_a_downgrade(self):
-        assert_raises_message(
-            util.CommandError,
-            "Not a valid downgrade target from current heads",
-            self.env._downgrade_revs,
-            self.d2.revision,
-            [self.d1.revision, self.d2.revision],
-        )
-
     def test_upgrade_from_base(self):
         self._assert_upgrade(
             "base+1", [], [self.up_(self.a)], set([self.a.revision])
@@ -544,6 +540,21 @@ class BranchedPathTest(MigrationTest):
             [],
         )
 
+    def test_downgrade_no_effect_branched(self):
+        """Added for good measure when there are multiple branches. """
+        self._assert_downgrade(
+            self.c2.revision,
+            [self.d1.revision, self.c2.revision],
+            [],
+            set([self.d1.revision, self.c2.revision]),
+        )
+        self._assert_downgrade(
+            self.d1.revision,
+            [self.d1.revision, self.c2.revision],
+            [],
+            set([self.d1.revision, self.c2.revision]),
+        )
+
 
 class BranchFromMergepointTest(MigrationTest):