Merge pull request #280 from sumpfgottheit/sqla_inheritance_primary_key

process inherited primary keys correctly

flask_admin/contrib/sqla/form.py

@@ -12,6 +12,7 @@ from flask.ext.admin._compat import iteritems
 
 from .validators import Unique
 from .fields import QuerySelectField, QuerySelectMultipleField, InlineModelFormList
+from .tools import is_inherited_primary_key, get_column_for_current_model
 
 try:
     # Field has better input parsing capabilities.
@@ -132,10 +133,13 @@ class AdminModelConverter(ModelConverterBase):
             if hasattr(prop, 'columns'):
                 # Check if more than one column mapped to the property
                 if len(prop.columns) != 1:
-                    raise TypeError('Can not convert multiple-column properties (%s.%s)' % (model, prop.key))
-
-                # Grab column
-                column = prop.columns[0]
+                    if is_inherited_primary_key(prop):
+                        column = get_column_for_current_model(prop)
+                    else:
+                        raise TypeError('Can not convert multiple-column properties (%s.%s)' % (model, prop.key))
+                else:
+                    # Grab column
+                    column = prop.columns[0]
 
                 # Do not display foreign keys - use relations
                 if column.foreign_keys:

flask_admin/contrib/sqla/tools.py

@@ -25,3 +25,39 @@ def get_primary_key(model):
                     return p.key
 
     return None
+
+def is_inherited_primary_key(prop):
+    """
+        Return True, if the ColumnProperty is an inherited primary key
+
+        Check if all columns are primary keys and _one_ does not have a foreign key -> looks like joined
+        table inheritance: http://docs.sqlalchemy.org/en/latest/orm/inheritance.html with "standard
+        practice" of same column name.
+
+        :param prop: The ColumnProperty to check
+        :return: Boolean
+        :raises: Exceptions as they occur - no ExceptionHandling here
+    """
+    return len([column for column in prop.columns if column.primary_key]) == len(prop.columns) and \
+                len([column for column in prop.columns if column.foreign_keys]) == len(prop.columns)-1
+
+def get_column_for_current_model(prop):
+    """
+        Return the Column() of the ColumnProperty "prop", that refers to the current model
+
+        When using inheritance, a ColumnProperty may contain multiple columns. This function
+        returns the Column(), the belongs to the Model of the ColumnProperty - the "current"
+        model
+
+        :param prop: The ColumnProperty
+        :return: The column for the current model
+        :raises: TypeError if not exactely one Column() for the current model could be found.
+                    All other Exceptions not handled here but raised
+    """
+    candidates = [column for column in prop.columns if column.expression == prop.expression]
+    if len(candidates) != 1:
+        raise TypeError('Not exactly one column for the current model found. ' +
+                        'Found %d columns for property %s' % (len(candidates), prop))
+    else:
+        return candidates[0]
+

flask_admin/contrib/sqla/view.py

@@ -15,7 +15,7 @@ from flask.ext.admin._backwards import ObsoleteAttr
 
 from flask.ext.admin.contrib.sqla import form, filters, tools
 from .typefmt import DEFAULT_FORMATTERS
-
+from .tools import is_inherited_primary_key, get_column_for_current_model
 
 class ModelView(BaseModelView):
     """
@@ -308,10 +308,18 @@ class ModelView(BaseModelView):
                 if self.column_display_all_relations or p.direction.name == 'MANYTOONE':
                     columns.append(p.key)
             elif hasattr(p, 'columns'):
-                # TODO: Check for multiple columns
-                column = p.columns[0]
+                column_inherited_primary_key = False
+                if len(p.columns) != 1:
+                    if is_inherited_primary_key(p):
+                        column = get_column_for_current_model(p)
+                    else:
+                        raise TypeError('Can not convert multiple-column properties (%s.%s)' % (model, p.key))
+                else:
+                    # Grab column
+                    column = p.columns[0]
 
-                if column.foreign_keys:
+                # An inherited primary key has a foreign key as well
+                if column.foreign_keys and not is_inherited_primary_key(p):
                     continue
 
                 if not self.column_display_pk and column.primary_key: