EnvironmentContext.get_revision_arguments() and EnvironmentContext.get_head_revisions() returns incorrect values

[sqlalchemy-bot]

Migrated issue, originally created by Dimitry Lukashov

When there are multiple active heads and the alembic_version table has multiple records
Script.as_revision_number() should return a tuple, instead it returns only returns the hex identifier of one of the heads, making EnvironmentContext.get_head_revisions() useless and EnvironmentContext.get_revision_arguments() not very helpful when there are multiple heads.

Here is my proposed solution:

--- a/alembic/runtime/environment.py
+++ b/alembic/runtime/environment.py
@@ -201,8 +201,9 @@ class EnvironmentContext(util.ModuleClsProxy):
         ``upgrade`` or ``downgrade`` command.
 
         If it was specified as ``head``, the actual
-        version number is returned; if specified
-        as ``base``, ``None`` is returned.
+        version number is returned; if specified as
+        ``heads`` a tuple of version numbers is returned;
+        if specified as ``base``, ``None`` is returned.
 
         This function does not require that the :class:`.MigrationContext`
         has been configured.
diff --git a/alembic/script/base.py b/alembic/script/base.py
index 2e6e0fb..419fce8 100644
--- a/alembic/script/base.py
+++ b/alembic/script/base.py
@@ -228,7 +228,7 @@ class ScriptDirectory(object):
             return self.revision_map.get_revision(id_)
 
     def as_revision_number(self, id_):
-        """Convert a symbolic revision, i.e. 'head' or 'base', into
+        """Convert a symbolic revision, i.e. 'head', 'heads' or 'base', into
         an actual revision number."""
 
         with self._catch_revision_errors():
@@ -237,6 +237,9 @@ class ScriptDirectory(object):
         if not rev:
             # convert () to None
             return None
+        elif id_ == 'heads':
+            # expects a tuple
+            return rev
         else:
             return rev[0]

[sqlalchemy-bot]

Dimitry Lukashov wrote:

PS I tried to submit a pull request and got a repository access denied. error.

[sqlalchemy-bot]

Michael Bayer (@zzzeek) wrote:

bitbucket's pull request feature gave you that error? I also don't accept PRs without tests in any case. it appears that get_head_revisions() was added without any tests at that time. there is no get_revision_arguments() method so I don't know what you're referring to (there's a get_revision_argument() method, which I don't see how that is related - test cases tell all, thanks).

[sqlalchemy-bot]

Michael Bayer (@zzzeek) wrote:

get_head_revisions() returning a tuple in all cases is going to break an application that expected this to be a straight string earlier, even though it is documented as returning a tuple. Hopefully this will not have a large impact as the method is entirely wrong right now returning a scalar value.

[sqlalchemy-bot]

Michael Bayer (@zzzeek) wrote:

https://gerrit.sqlalchemy.org/#/c/zzzeek/alembic/+/668

[sqlalchemy-bot]

Michael Bayer (@zzzeek) wrote:

Repair as_revision_number to return a tuple for "heads"

Fixed bug where the :meth:.Script.as_revision_number method
did not accommodate for the 'heads' identifier, which in turn
caused the :meth:.EnvironmentContext.get_head_revisions
and :meth:.EnvironmentContext.get_revision_argument methods
to be not usable when multiple heads were present.
The :meth:.EnvironmentContext.get_head_revisions method returns
a tuple in all cases as documented.

Change-Id: I085d9b6c3f4ceafd6828d24983768a3d3916ce00
Fixes: #482

→ 3c726b2

[sqlalchemy-bot]

Changes by Michael Bayer (@zzzeek):

• changed status to closed

[sqlalchemy-bot]

Dimitry Lukashov wrote:

@zzzeek thank you very much! Do you normally allow others to PR, if yes, then it must be a problem on my end. Next time I will add test cases!