Merge pull request #326 from edx/ekolpakov/force_export

Force export runtime option + some tests for XmlSerializationMixin

xblock/fields.py

@@ -298,6 +298,9 @@ class will want to refer to.
         xml_node: if set, the field will be serialized as a
             separate node instead of an xml attribute (default: False).
 
+        force_export: if set, the field value will be exported to XML even if normal
+            export conditions are not met (i.e. the field has no explicit value set)
+
         kwargs: optional runtime-specific options/metadata. Will be stored as
             runtime_options.
 
@@ -308,7 +311,7 @@ class will want to refer to.
     # We're OK redefining built-in `help`
     def __init__(self, help=None, default=UNSET, scope=Scope.content,  # pylint:disable=redefined-builtin
                  display_name=None, values=None, enforce_type=False,
-                 xml_node=False, **kwargs):
+                 xml_node=False, force_export=False, **kwargs):
         self.warned = False
         self.help = help
         self._enable_enforce_type = enforce_type
@@ -322,6 +325,7 @@ def __init__(self, help=None, default=UNSET, scope=Scope.content,  # pylint:disa
         self._values = values
         self.runtime_options = kwargs
         self.xml_node = xml_node
+        self.force_export = force_export
 
     @property
     def default(self):

xblock/mixins.py

@@ -8,6 +8,7 @@
 import logging
 from lxml import etree
 import copy
+from collections import OrderedDict
 
 try:
     import simplesjson as json  # pylint: disable=F0401
@@ -22,10 +23,12 @@
 from xblock.internal import class_lazy, NamedAttributesMetaclass
 
 
-XML_NAMESPACES = {
-    "option": "http://code.edx.org/xblock/option",
-    "block": "http://code.edx.org/xblock/block",
-}
+# OrderedDict is used so that namespace attributes are put in predictable order
+# This allows for simple string equality assertions in tests and have no other effects
+XML_NAMESPACES = OrderedDict([
+    ("option", "http://code.edx.org/xblock/option"),
+    ("block", "http://code.edx.org/xblock/block"),
+])
 
 
 class HandlersMixin(object):
@@ -477,7 +480,7 @@ def add_xml_to_node(self, node):
         for field_name, field in self.fields.iteritems():
             if field_name in ('children', 'parent', 'content'):
                 continue
-            if field.is_set_on(self):
+            if field.is_set_on(self) or field.force_export:
                 self._add_field(node, field_name, field)
 
         # Add children for each of our children.

xblock/test/test_mixins.py

@@ -1,11 +1,15 @@
 """
 Tests of the XBlock-family functionality mixins
 """
-
+from lxml import etree
+import mock
 from unittest import TestCase
 
-from xblock.fields import List, Scope, Integer
+from xblock.core import XBlock
+from xblock.fields import List, Scope, Integer, String, ScopeIds, UNIQUE_ID
+from xblock.field_data import DictFieldData
 from xblock.mixins import ScopedStorageMixin, HierarchyMixin, IndexInfoMixin, ViewsMixin
+from xblock.runtime import Runtime
 
 
 class AttrAssertionMixin(TestCase):
@@ -209,3 +213,73 @@ def has_support(self, view, functionality):
                 test_xblock.has_support(getattr(test_xblock, view_name, None), functionality),
                 expected_result
             )
+
+
+class TestXmlSerializationMixin(TestCase):
+    """ Tests for XmlSerialization Mixin """
+
+    etree_node_tag = 'test_xblock'
+
+    # pylint:disable=invalid-name
+    class TestXBlock(XBlock):
+        """ XBlock for XML export test """
+        field = String()
+        simple_default = String(default="default")
+        simple_default_with_force_export = String(default="default", force_export=True)
+        unique_id_default = String(default=UNIQUE_ID)
+        unique_id_default_with_force_export = String(default=UNIQUE_ID, force_export=True)
+
+    def _make_block(self):
+        """ Creates a test block """
+        runtime_mock = mock.Mock(spec=Runtime)
+        scope_ids = ScopeIds("user_id", self.etree_node_tag, "def_id", "usage_id")
+        return self.TestXBlock(runtime_mock, field_data=DictFieldData({}), scope_ids=scope_ids)
+
+    def _assert_node_attributes(self, node, attributes):
+        """ Asserts node attributes """
+        node_attributes = node.keys()
+        node_attributes.remove('xblock-family')
+
+        self.assertEqual(node.get('xblock-family'), self.TestXBlock.entry_point)
+
+        self.assertEqual(set(node_attributes), set(attributes.keys()))
+
+        for key, value in attributes.iteritems():
+            if value != UNIQUE_ID:
+                self.assertEqual(node.get(key), value)
+            else:
+                self.assertIsNotNone(node.get(key))
+
+    def test_add_xml_to_node(self):
+        """ Tests add_xml_to_node with various field defaults and runtime parameters """
+        block = self._make_block()
+        node = etree.Element(self.etree_node_tag)
+
+        # precondition check
+        for field_name in block.fields.keys():
+            self.assertFalse(block.fields[field_name].is_set_on(block))
+
+        block.add_xml_to_node(node)
+
+        self._assert_node_attributes(
+            node, {'simple_default_with_force_export': 'default', 'unique_id_default_with_force_export': UNIQUE_ID}
+        )
+
+        block.field = 'Value1'
+        block.simple_default = 'Value2'
+        block.simple_default_with_force_export = 'Value3'
+        block.unique_id_default = 'Value4'
+        block.unique_id_default_with_force_export = 'Value5'
+
+        block.add_xml_to_node(node)
+
+        self._assert_node_attributes(
+            node,
+            {
+                'field': 'Value1',
+                'simple_default': 'Value2',
+                'simple_default_with_force_export': 'Value3',
+                'unique_id_default': 'Value4',
+                'unique_id_default_with_force_export': 'Value5',
+            }
+        )