Implement Mypy plugin

Rudimentary and experimental support for Mypy has been added in the form of
a new plugin, which itself depends on new typing stubs for SQLAlchemy. The
plugin allows declarative mappings in their standard form to both be
compatible with Mypy as well as to provide typing support for mapped
classes and instances.

Fixes: #4609
Change-Id: Ia035978c02ad3a5c0e5b3c6c30044dd5a3155170

1 files changed, 12 insertions, 0 deletions

diff --git a/lib/sqlalchemy/testing/requirements.py b/lib/sqlalchemy/testing/requirements.py
index f16ba326c..de2b8f12c 100644
--- a/lib/sqlalchemy/testing/requirements.py
+++ b/lib/sqlalchemy/testing/requirements.py
@@ -1173,6 +1173,18 @@ class SuiteRequirements(Requirements):
         )
 
     @property
+    def sqlalchemy2_stubs(self):
+        def check(config):
+            try:
+                __import__("sqlalchemy-stubs.ext.mypy")
+            except ImportError:
+                return False
+            else:
+                return True
+
+        return exclusions.only_if(check)
+
+    @property
     def python2(self):
         return exclusions.skip_if(
             lambda: sys.version_info >= (3,),