fix: make master view auto-detect continuum versioning for model class

src/wuttaweb/views/master.py

@@ -350,14 +350,6 @@ class MasterView(View):  # pylint: disable=too-many-public-methods
        "configuring" - i.e. it should have a :meth:`configure()` view.
        Default value is ``False``.
 
-    .. attribute:: has_versions
-
-       Boolean indicating whether the master view should expose
-       version history for its data records - i.e. it should have a
-       :meth:`view_versions()` view.  Default value is ``False``.
-
-       See also :meth:`should_expose_versions()`.
-
     .. attribute:: version_grid_columns
 
        List of columns for the :meth:`view_versions()` view grid.
@@ -451,9 +443,6 @@ class MasterView(View):  # pylint: disable=too-many-public-methods
     rows_paginate_on_backend = True
     rows_viewable = False
 
-    # versioning features
-    has_versions = False
-
     # current action
     listing = False
     creating = False
@@ -914,12 +903,40 @@ class MasterView(View):  # pylint: disable=too-many-public-methods
     # version history methods
     ##############################
 
+    @classmethod
+    def is_versioned(cls):
+        """
+        Returns boolean indicating whether the model class is
+        configured for SQLAlchemy-Continuum versioning.
+
+        The default logic will directly inspect the model class, as
+        returned by :meth:`get_model_class()`.  Or you can override by
+        setting the ``model_is_versioned`` attribute::
+
+           class WidgetView(MasterView):
+               model_class = Widget
+               model_is_versioned = False
+
+        See also :meth:`should_expose_versions()`.
+
+        :returns: ``True`` if the model class is versioned; else
+           ``False``.
+        """
+        if hasattr(cls, "model_is_versioned"):
+            return cls.model_is_versioned
+
+        model_class = cls.get_model_class()
+        if hasattr(model_class, "__versioned__"):
+            return True
+
+        return False
+
     @classmethod
     def get_model_version_class(cls):
         """
         Returns the version class for the master model class.
 
-        Should only be relevant if :attr:`has_versions` is true.
+        Should only be relevant if :meth:`is_versioned()` is true.
         """
         import sqlalchemy_continuum as continuum  # pylint: disable=import-outside-toplevel
 
@@ -931,14 +948,14 @@ class MasterView(View):  # pylint: disable=too-many-public-methods
         be exposed for the current user.  This will return ``True``
         unless any of the following are ``False``:
 
-        * :attr:`has_versions`
+        * :meth:`is_versioned()`
         * :meth:`wuttjamaican:wuttjamaican.app.AppHandler.continuum_is_enabled()`
         * ``self.has_perm("versions")`` - cf. :meth:`has_perm()`
 
         :returns: ``True`` if versioning should be exposed for current
            user; else ``False``.
         """
-        if not self.has_versions:
+        if not self.is_versioned():
             return False
 
         if not self.app.continuum_is_enabled():
@@ -958,8 +975,8 @@ class MasterView(View):  # pylint: disable=too-many-public-methods
         ``/widgets/XXX/versions/`` where ``XXX`` represents the key/ID
         for the record.
 
-        By default, this view is included only if :attr:`has_versions`
-        is true.
+        By default, this view is included only if
+        :meth:`is_versioned()` is true.
 
         The default view logic will show a "grid" (table) with the
         record's version history.
@@ -1147,8 +1164,8 @@ class MasterView(View):  # pylint: disable=too-many-public-methods
         key/ID for the record and YYY represents a
         SQLAlchemy-Continuum ``transaction.id``.
 
-        By default, this view is included only if :attr:`has_versions`
-        is true.
+        By default, this view is included only if
+        :meth:`is_versioned()` is true.
 
         The default view logic will display a "diff" table showing how
         the record's values were changed within a transaction.
@@ -3618,7 +3635,7 @@ class MasterView(View):  # pylint: disable=too-many-public-methods
             )
 
         # version history
-        if cls.has_versions and app.continuum_is_enabled():
+        if cls.is_versioned() and app.continuum_is_enabled():
             instance_url_prefix = cls.get_instance_url_prefix()
             config.add_wutta_permission(
                 permission_prefix,

tests/views/test_master.py

@@ -1849,10 +1849,24 @@ class TestVersionedMasterView(VersionWebTestCase):
     def make_view(self):
         return mod.MasterView(self.request)
 
+    def test_is_versioned(self):
+        model = self.app.model
+
+        with patch.object(mod.MasterView, "model_class", new=model.User):
+
+            # User is versioned by default
+            self.assertTrue(mod.MasterView.is_versioned())
+
+            # but view can override w/ attr
+            with patch.object(
+                mod.MasterView, "model_is_versioned", new=False, create=True
+            ):
+                self.assertFalse(mod.MasterView.is_versioned())
+
     def test_defaults(self):
         model = self.app.model
 
-        with patch.multiple(mod.MasterView, model_class=model.User, has_versions=True):
+        with patch.object(mod.MasterView, "model_class", new=model.User):
             mod.MasterView.defaults(self.pyramid_config)
 
     def test_get_model_version_class(self):
@@ -1864,7 +1878,7 @@ class TestVersionedMasterView(VersionWebTestCase):
 
     def test_should_expose_versions(self):
         model = self.app.model
-        with patch.multiple(mod.MasterView, model_class=model.User, has_versions=True):
+        with patch.object(mod.MasterView, "model_class", new=model.User):
 
             # fully enabled for root user
             with patch.object(self.request, "is_root", new=True):