LazyCryptContext is used for the lazy configuration of the PasswordType.

sqlalchemy_utils/types/password.py

@@ -11,7 +11,7 @@ from .scalar_coercible import ScalarCoercible
 passlib = None
 try:
     import passlib
-    from passlib.context import CryptContext
+    from passlib.context import LazyCryptContext
 except ImportError:
     pass
 
@@ -82,7 +82,7 @@ class PasswordType(types.TypeDecorator, ScalarCoercible):
     verifying them using a pythonic interface.
 
     All keyword arguments (aside from max_length) are forwarded to the
-    construction of a `passlib.context.CryptContext` object.
+    construction of a `passlib.context.LazyCryptContext` object.
 
     The following usage will create a password column that will
     automatically hash new passwords as `pbkdf2_sha512` but still compare
@@ -128,7 +128,7 @@ class PasswordType(types.TypeDecorator, ScalarCoercible):
             )
 
         # Construct the passlib crypt context.
-        self.context = CryptContext(**kwargs)
+        self.context = LazyCryptContext(**kwargs)
 
         if max_length is None:
             max_length = self.calculate_max_length()

tests/types/test_password.py

@@ -6,7 +6,13 @@ from sqlalchemy_utils import Password, PasswordType, types  # noqa
 
 
 @pytest.fixture
-def User(Base):
+def extra_kwargs():
+    """PasswordType extra keyword arguments."""
+    return {}
+
+
+@pytest.fixture
+def User(Base, extra_kwargs):
     class User(Base):
         __tablename__ = 'user'
         id = sa.Column(sa.Integer, primary_key=True)
@@ -17,8 +23,8 @@ def User(Base):
                 'md5_crypt',
                 'hex_md5'
             ],
-
-            deprecated=['md5_crypt', 'hex_md5']
+            deprecated=['md5_crypt', 'hex_md5'],
+            **extra_kwargs
         ))
 
         def __repr__(self):
@@ -31,6 +37,17 @@ def init_models(User):
     pass
 
 
+def onload_callback(schemes, deprecated):
+    """
+    Get onload callback that takes the PasswordType arguments from the config.
+    """
+    def onload(**kwargs):
+        kwargs['schemes'] = schemes
+        kwargs['deprecated'] = deprecated
+        return kwargs
+    return onload
+
+
 @pytest.mark.skipif('types.password.passlib is None')
 class TestPasswordType(object):
 
@@ -178,3 +195,25 @@ class TestPasswordType(object):
 
         assert obj.password.hash.decode('utf8').startswith('$pbkdf2-sha512$')
         assert obj.password == 'b'
+
+    @pytest.mark.parametrize(
+        'extra_kwargs',
+        [
+            dict(
+                onload=onload_callback(
+                    schemes=['pbkdf2_sha256'],
+                    deprecated=[],
+                )
+            )
+        ]
+    )
+    def test_lazy_configuration(self, User):
+        """
+        Field should be able to read the passlib attributes lazily from the
+        config (e.g. Flask config).
+        """
+        schemes = User.password.type.context.schemes()
+        assert tuple(schemes) == ('pbkdf2_sha256',)
+        obj = User()
+        obj.password = b'b'
+        assert obj.password.hash.decode('utf8').startswith('$pbkdf2-sha256$')