refactor: Extract sqlalchemy compat into its own module.

src/pytest_mock_resources/compat/__init__.py

@@ -1,27 +1,7 @@
-class ImportAdaptor(object):
-    __wrapped__ = False
-
-    def __init__(self, package, recommended_extra, fail_message=None, **attrs):
-        self.package = package
-        self.recommended_extra = recommended_extra
-        self.fail_message = fail_message
-
-        for key, value in attrs.items():
-            setattr(self, key, value)
-
-    def fail(self):
-        if self.fail_message:
-            fail_message = self.fail_message
-        else:
-            fail_message = "Cannot use {recommended_extra} fixtures without {package}. pip install pytest-mock-resources[{recommended_extra}]".format(
-                package=self.package, recommended_extra=self.recommended_extra
-            )
-
-        raise RuntimeError(fail_message)
-
-    def __getattr__(self, attr):
-        self.fail()
+from pytest_mock_resources.compat.import_ import ImportAdaptor
 
+# isort: split
+from pytest_mock_resources.compat import import_, sqlalchemy  # flake8: ignore
 
 try:
     import psycopg2
@@ -88,12 +68,3 @@ def __getattr__(self, attr):
     import pymysql
 except ImportError:
     pymysql = ImportAdaptor("pymysql", "mysql")  # type: ignore
-
-try:
-    from sqlalchemy.ext import asyncio as sqlalchemy_asyncio  # type: ignore
-except ImportError:
-    sqlalchemy_asyncio = ImportAdaptor(  # type: ignore
-        "SQLAlchemy",
-        "SQLAlchemy >= 1.4",
-        fail_message="Cannot use sqlalchemy async features with SQLAlchemy < 1.4.\n",
-    )

src/pytest_mock_resources/compat/import_.py

@@ -0,0 +1,23 @@
+class ImportAdaptor(object):
+    __wrapped__ = False
+
+    def __init__(self, package, recommended_extra, fail_message=None, **attrs):
+        self.package = package
+        self.recommended_extra = recommended_extra
+        self.fail_message = fail_message
+
+        for key, value in attrs.items():
+            setattr(self, key, value)
+
+    def fail(self):
+        if self.fail_message:
+            fail_message = self.fail_message
+        else:
+            fail_message = "Cannot use {recommended_extra} fixtures without {package}. pip install pytest-mock-resources[{recommended_extra}]".format(
+                package=self.package, recommended_extra=self.recommended_extra
+            )
+
+        raise RuntimeError(fail_message)
+
+    def __getattr__(self, attr):
+        self.fail()

src/pytest_mock_resources/compat/sqlalchemy.py

@@ -0,0 +1,10 @@
+from pytest_mock_resources.compat.import_ import ImportAdaptor
+
+try:
+    from sqlalchemy.ext import asyncio as asyncio  # type: ignore
+except ImportError:
+    asyncio = ImportAdaptor(  # type: ignore
+        "SQLAlchemy",
+        "SQLAlchemy >= 1.4",
+        fail_message="Cannot use sqlalchemy async features with SQLAlchemy < 1.4.\n",
+    )

src/pytest_mock_resources/fixture/database/relational/generic.py

@@ -11,7 +11,7 @@
 from sqlalchemy.sql.ddl import CreateSchema
 from sqlalchemy.sql.schema import Table
 
-from pytest_mock_resources.compat import sqlalchemy_asyncio
+from pytest_mock_resources import compat
 
 
 @six.add_metaclass(abc.ABCMeta)
@@ -188,7 +188,9 @@ async def manage_async(self, session=None):
                     session_factory = session
                 else:
                     session_factory = sessionmaker(
-                        async_engine, expire_on_commit=False, class_=sqlalchemy_asyncio.AsyncSession
+                        async_engine,
+                        expire_on_commit=False,
+                        class_=compat.sqlalchemy.asyncio.AsyncSession,
                     )
                 async with session_factory() as session:
                     yield session
@@ -210,7 +212,7 @@ def _get_async_engine(self, isolation_level=None):
         options = {}
         if isolation_level:
             options["isolation_level"] = isolation_level
-        return sqlalchemy_asyncio.create_async_engine(url, **options)
+        return compat.sqlalchemy.asyncio.create_async_engine(url, **options)
 
 
 def identify_matching_tables(metadata, table_specifier):