Don't import provision.py unconditionally

Removed the imports for provision.py from each dialect
and instead added a call in the central provision.py to
a new dialect level method load_provisioning().  The
provisioning registry works in the same way, so an existing
dialect that is using the provision.py system right now
by importing it as part of the package will still continue to
function.  However, to avoid pulling in the testing package when
the dialect is used in a non-testing context, the new hook may be
used.   Also removed a module-level dependency
of the testing framework on the orm package.

Revised an internal change to the test system added as a result of
:ticket:`5085` where a testing-related module per dialect would be loaded
unconditionally upon making use of that dialect, pulling in SQLAlchemy's
testing framework as well as the ORM into the module import space.   This
would only impact initial startup time and memory to a modest extent,
however it's best that these additional modules aren't reverse-dependent on
straight Core usage.

Fixes: #5180
Change-Id: I6355601da5f6f44d85a2bbc3acb5928559942b9c

10 files changed, 42 insertions, 9 deletions

diff --git a/lib/sqlalchemy/dialects/mssql/__init__.py b/lib/sqlalchemy/dialects/mssql/__init__.py
index cbee8c0dc..67830affe 100644
--- a/lib/sqlalchemy/dialects/mssql/__init__.py
+++ b/lib/sqlalchemy/dialects/mssql/__init__.py
@@ -8,7 +8,6 @@
 from . import adodbapi  # noqa
 from . import base  # noqa
 from . import mxodbc  # noqa
-from . import provision  # noqa
 from . import pymssql  # noqa
 from . import pyodbc  # noqa
 from .base import BIGINT
diff --git a/lib/sqlalchemy/dialects/mysql/__init__.py b/lib/sqlalchemy/dialects/mysql/__init__.py
index 12eb673a7..f1f1cce37 100644
--- a/lib/sqlalchemy/dialects/mysql/__init__.py
+++ b/lib/sqlalchemy/dialects/mysql/__init__.py
@@ -11,7 +11,6 @@ from . import gaerdbms  # noqa
 from . import mysqlconnector  # noqa
 from . import mysqldb  # noqa
 from . import oursql  # noqa
-from . import provision  # noqa
 from . import pymysql  # noqa
 from . import pyodbc  # noqa
 from .base import BIGINT
diff --git a/lib/sqlalchemy/dialects/oracle/__init__.py b/lib/sqlalchemy/dialects/oracle/__init__.py
index 90157bd67..a4dee02ff 100644
--- a/lib/sqlalchemy/dialects/oracle/__init__.py
+++ b/lib/sqlalchemy/dialects/oracle/__init__.py
@@ -7,7 +7,6 @@
 
 from . import base  # noqa
 from . import cx_oracle  # noqa
-from . import provision  # noqa
 from .base import BFILE
 from .base import BINARY_DOUBLE
 from .base import BINARY_FLOAT
diff --git a/lib/sqlalchemy/dialects/postgresql/__init__.py b/lib/sqlalchemy/dialects/postgresql/__init__.py
index c6482222d..06d22872a 100644
--- a/lib/sqlalchemy/dialects/postgresql/__init__.py
+++ b/lib/sqlalchemy/dialects/postgresql/__init__.py
@@ -7,7 +7,6 @@
 
 from . import base
 from . import pg8000  # noqa
-from . import provision  # noqa
 from . import psycopg2  # noqa
 from . import psycopg2cffi  # noqa
 from . import pygresql  # noqa
diff --git a/lib/sqlalchemy/dialects/sqlite/__init__.py b/lib/sqlalchemy/dialects/sqlite/__init__.py
index c35cb9251..142131f63 100644
--- a/lib/sqlalchemy/dialects/sqlite/__init__.py
+++ b/lib/sqlalchemy/dialects/sqlite/__init__.py
@@ -6,7 +6,6 @@
 # the MIT License: http://www.opensource.org/licenses/mit-license.php
 
 from . import base  # noqa
-from . import provision  # noqa
 from . import pysqlcipher  # noqa
 from . import pysqlite  # noqa
 from .base import BLOB
diff --git a/lib/sqlalchemy/engine/default.py b/lib/sqlalchemy/engine/default.py
index 28a59e660..8775a8813 100644
--- a/lib/sqlalchemy/engine/default.py
+++ b/lib/sqlalchemy/engine/default.py
@@ -293,6 +293,14 @@ class DefaultDialect(interfaces.Dialect):
     def get_pool_class(cls, url):
         return getattr(cls, "poolclass", pool.QueuePool)
 
+    @classmethod
+    def load_provisioning(cls):
+        package = ".".join(cls.__module__.split(".")[0:-1])
+        try:
+            __import__(package + ".provision")
+        except ImportError:
+            pass
+
     def initialize(self, connection):
         try:
             self.server_version_info = self._get_server_version_info(
diff --git a/lib/sqlalchemy/engine/interfaces.py b/lib/sqlalchemy/engine/interfaces.py
index 04e572c2d..84def853f 100644
--- a/lib/sqlalchemy/engine/interfaces.py
+++ b/lib/sqlalchemy/engine/interfaces.py
@@ -866,6 +866,35 @@ class Dialect(object):
         return cls
 
     @classmethod
+    def load_provisioning(cls):
+        """set up the provision.py module for this dialect.
+
+        For dialects that include a provision.py module that sets up
+        provisioning followers, this method should initiate that process.
+
+        A typical implementation would be::
+
+            @classmethod
+            def load_provisioning(cls):
+                __import__("mydialect.provision")
+
+        The default method assumes a module named ``provision.py`` inside
+        the owning package of the current dialect, based on the ``__module__``
+        attribute::
+
+            @classmethod
+            def load_provisioning(cls):
+                package = ".".join(cls.__module__.split(".")[0:-1])
+                try:
+                    __import__(package + ".provision")
+                except ImportError:
+                    pass
+
+        .. versionadded:: 1.3.14
+
+        """
+
+    @classmethod
     def engine_created(cls, engine):
         """A convenience hook called before returning the final :class:`.Engine`.
 
diff --git a/lib/sqlalchemy/orm/query.py b/lib/sqlalchemy/orm/query.py
index e29e6eeee..830cede93 100644
--- a/lib/sqlalchemy/orm/query.py
+++ b/lib/sqlalchemy/orm/query.py
@@ -59,7 +59,6 @@ from ..sql.base import Generative
 from ..sql.selectable import ForUpdateArg
 from ..util import collections_abc
 
-
 __all__ = ["Query", "QueryContext", "aliased"]
 
 
diff --git a/lib/sqlalchemy/testing/assertions.py b/lib/sqlalchemy/testing/assertions.py
index c97202516..07a70bf6c 100644
--- a/lib/sqlalchemy/testing/assertions.py
+++ b/lib/sqlalchemy/testing/assertions.py
@@ -19,7 +19,6 @@ from . import mock
 from .exclusions import db_spec
 from .util import fail
 from .. import exc as sa_exc
-from .. import orm
 from .. import schema
 from .. import types as sqltypes
 from .. import util
@@ -386,6 +385,8 @@ class AssertsCompiledSQL(object):
         if render_postcompile:
             compile_kwargs["render_postcompile"] = True
 
+        from sqlalchemy import orm
+
         if isinstance(clause, orm.Query):
             context = clause._compile_context()
             context.statement.use_labels = True
diff --git a/lib/sqlalchemy/testing/provision.py b/lib/sqlalchemy/testing/provision.py
index 6e2e1ccf5..543d91a53 100644
--- a/lib/sqlalchemy/testing/provision.py
+++ b/lib/sqlalchemy/testing/provision.py
@@ -6,7 +6,6 @@ from . import engines
 from ..engine import url as sa_url
 from ..util import compat
 
-
 log = logging.getLogger(__name__)
 
 FOLLOWER_IDENT = None
@@ -51,7 +50,9 @@ def setup_config(db_url, options, file_config, follower_ident):
     # load the dialect, which should also have it set up its provision
     # hooks
 
-    sa_url.make_url(db_url).get_dialect()
+    dialect = sa_url.make_url(db_url).get_dialect()
+    dialect.load_provisioning()
+
     if follower_ident:
         db_url = follower_url_from_main(db_url, follower_ident)
     db_opts = {}