this is all tests passing with the refactor, which IMHO is

miraculous

1 files changed, 55 insertions, 17 deletions

diff --git a/alembic/migration.py b/alembic/migration.py
index 69e6930..733727d 100644
--- a/alembic/migration.py
+++ b/alembic/migration.py
@@ -4,7 +4,7 @@ from sqlalchemy import MetaData, Table, Column, String, literal_column, \
 from sqlalchemy import create_engine
 from alembic import ddl
 import sys
-from contextlib import contextmanager
+from sqlalchemy.engine import url as sqla_url
 
 import logging
 log = logging.getLogger(__name__)
@@ -21,22 +21,19 @@ class MigrationContext(object):
     Mediates the relationship between an ``env.py`` environment script, 
     a :class:`.ScriptDirectory` instance, and a :class:`.DefaultImpl` instance.
 
-    The :class:`.Context` is available directly via the :func:`.get_context` function,
+    The :class:`.MigrationContext` is available directly via the :func:`.get_context` function,
     though usually it is referenced behind the scenes by the various module level functions
     within the :mod:`alembic.context` module.
 
     """
-    def __init__(self, dialect, script, connection, 
-                        opts,
-                        as_sql=False, 
-                        output_buffer=None,
-                        transactional_ddl=None,
-                        starting_rev=None,
-                        compare_type=False,
-                        compare_server_default=False):
+    def __init__(self, dialect, connection, opts):
+        self.opts = opts
         self.dialect = dialect
-        # TODO: need this ?
-        self.script = script
+        self.script = opts.get('script')
+
+        as_sql=opts.get('as_sql', False)
+        transactional_ddl=opts.get("transactional_ddl")
+
         if as_sql:
             self.connection = self._stdout_connection(connection)
             assert self.connection is not None
@@ -44,12 +41,12 @@ class MigrationContext(object):
             self.connection = connection
         self._migrations_fn = opts.get('fn')
         self.as_sql = as_sql
-        self.output_buffer = output_buffer if output_buffer else sys.stdout
+        self.output_buffer = opts.get("output_buffer", sys.stdout)
 
-        self._user_compare_type = compare_type
-        self._user_compare_server_default = compare_server_default
+        self._user_compare_type = opts.get('compare_type', False)
+        self._user_compare_server_default = opts.get('compare_server_default', False)
 
-        self._start_from_rev = starting_rev
+        self._start_from_rev = opts.get("starting_rev")
         self.impl = ddl.DefaultImpl.get_by_dialect(dialect)(
                             dialect, self.connection, self.as_sql,
                             transactional_ddl,
@@ -63,6 +60,46 @@ class MigrationContext(object):
                         "transactional" if self.impl.transactional_ddl 
                         else "non-transactional")
 
+    @classmethod
+    def configure(cls,
+                connection=None,
+                url=None,
+                dialect_name=None,
+                opts=None,
+    ):
+        """Create a new :class:`.MigrationContext`.
+        
+        This is a factory method usually called
+        by :meth:`.EnvironmentContext.configure`.
+        
+        :param connection: a :class:`~sqlalchemy.engine.base.Connection` to use
+         for SQL execution in "online" mode.  When present, is also used to 
+         determine the type of dialect in use.
+        :param url: a string database url, or a :class:`sqlalchemy.engine.url.URL` object.
+         The type of dialect to be used will be derived from this if ``connection`` is
+         not passed.
+        :param dialect_name: string name of a dialect, such as "postgresql", "mssql", etc.
+         The type of dialect to be used will be derived from this if ``connection``
+         and ``url`` are not passed.
+        :param opts: dictionary of options.  Most other options
+         accepted by :meth:`.EnvironmentContext.configure` are passed via 
+         this dictionary.
+
+        """
+        if connection:
+            dialect = connection.dialect
+        elif url:
+            url = sqla_url.make_url(url)
+            dialect = url.get_dialect()()
+        elif dialect_name:
+            url = sqla_url.make_url("%s://" % dialect_name)
+            dialect = url.get_dialect()()
+        else:
+            raise Exception("Connection, url, or dialect_name is required.")
+
+        return MigrationContext(dialect, connection, opts)
+
+
     def _current_rev(self):
         if self.as_sql:
             return self._start_from_rev
@@ -93,7 +130,8 @@ class MigrationContext(object):
         current_rev = rev = False
         self.impl.start_migrations()
         for change, prev_rev, rev in self._migrations_fn(
-                                        self._current_rev()):
+                                        self._current_rev(),
+                                        self):
             if current_rev is False:
                 current_rev = prev_rev
                 if self.as_sql and not current_rev: