refactor: refactor discussions_xblock (#30636)

JIRA: https://openedx.atlassian.net/browse/BOM-2580
This PR aims at refactoring the discussion xblock sub project and moving it within the xmodule directory effectively removing its position as a sub project within edx-platform

xmodule/tests/test_discussion.py

@@ -0,0 +1,186 @@
+""" Tests for DiscussionXBLock"""
+
+
+import itertools
+import random
+import string
+from collections import namedtuple
+from unittest import TestCase, mock
+
+import ddt
+from xblock.field_data import DictFieldData
+from xblock.fields import NO_CACHE_VALUE, UNIQUE_ID, ScopeIds
+from xblock.runtime import Runtime
+
+from openedx.core.lib.safe_lxml import etree
+from xmodule.discussion_block import DiscussionXBlock
+
+
+def attribute_pair_repr(self):
+    """
+    Custom string representation for the AttributePair namedtuple which is
+    consistent between test runs.
+    """
+    return f'<AttributePair name={self.name}>'
+
+
+AttributePair = namedtuple("AttributePair", ["name", "value"])
+AttributePair.__repr__ = attribute_pair_repr
+
+
+ID_ATTR_NAMES = ("discussion_id",)
+CATEGORY_ATTR_NAMES = ("discussion_category",)
+TARGET_ATTR_NAMES = ("discussion_target",)
+
+
+def _random_string():
+    """
+    Generates random string
+    """
+    return ''.join(random.choice(string.ascii_lowercase, ) for _ in range(12))
+
+
+def _make_attribute_test_cases():
+    """
+    Builds test cases for attribute-dependent tests
+    """
+    attribute_names = itertools.product(ID_ATTR_NAMES, CATEGORY_ATTR_NAMES, TARGET_ATTR_NAMES)
+    for id_attr, category_attr, target_attr in attribute_names:
+        yield (
+            AttributePair(id_attr, _random_string()),
+            AttributePair(category_attr, _random_string()),
+            AttributePair(target_attr, _random_string())
+        )
+
+
+@ddt.ddt
+class DiscussionXBlockImportExportTests(TestCase):
+    """
+    Import and export tests
+    """
+    DISCUSSION_XBLOCK_LOCATION = "xmodule.discussion_block.DiscussionXBlock"
+
+    def setUp(self):
+        """
+        Set up method
+        """
+        super().setUp()
+        self.keys = ScopeIds("any_user", "discussion", "def_id", "usage_id")
+        self.runtime_mock = mock.Mock(spec=Runtime)
+        self.runtime_mock.construct_xblock_from_class = mock.Mock(side_effect=self._construct_xblock_mock)
+        self.runtime_mock.get_policy = mock.Mock(return_value={})
+        self.id_gen_mock = mock.Mock()
+
+    def _construct_xblock_mock(self, cls, keys):  # pylint: disable=unused-argument
+        """
+        Builds target xblock instance (DiscussionXBlock)
+
+        Signature-compatible with runtime.construct_xblock_from_class - can be used as a mock side-effect
+        """
+        return DiscussionXBlock(self.runtime_mock, scope_ids=keys, field_data=DictFieldData({}))
+
+    @mock.patch(DISCUSSION_XBLOCK_LOCATION + ".load_definition_xml")
+    @ddt.unpack
+    @ddt.data(*list(_make_attribute_test_cases()))
+    def test_xblock_export_format(self, id_pair, category_pair, target_pair, patched_load_definition_xml):
+        """
+        Test that xblock export XML format can be parsed preserving field values
+        """
+        xblock_xml = """
+        <discussion
+            url_name="82bb87a2d22240b1adac2dfcc1e7e5e4" xblock-family="xblock.v1"
+            {id_attr}="{id_value}"
+            {category_attr}="{category_value}"
+            {target_attr}="{target_value}"
+        />
+        """.format(
+            id_attr=id_pair.name, id_value=id_pair.value,
+            category_attr=category_pair.name, category_value=category_pair.value,
+            target_attr=target_pair.name, target_value=target_pair.value,
+        )
+        node = etree.fromstring(xblock_xml)
+
+        patched_load_definition_xml.side_effect = Exception("Irrelevant")
+
+        block = DiscussionXBlock.parse_xml(node, self.runtime_mock, self.keys, self.id_gen_mock)
+        try:
+            assert block.discussion_id == id_pair.value
+            assert block.discussion_category == category_pair.value
+            assert block.discussion_target == target_pair.value
+        except AssertionError:
+            print(xblock_xml)
+            raise
+
+    @mock.patch(DISCUSSION_XBLOCK_LOCATION + ".load_definition_xml")
+    @ddt.unpack
+    @ddt.data(*(_make_attribute_test_cases()))
+    def test_legacy_export_format(self, id_pair, category_pair, target_pair, patched_load_definition_xml):
+        """
+        Test that legacy export XML format can be parsed preserving field values
+        """
+        xblock_xml = """<discussion url_name="82bb87a2d22240b1adac2dfcc1e7e5e4"/>"""
+        xblock_definition_xml = """
+        <discussion
+            {id_attr}="{id_value}"
+            {category_attr}="{category_value}"
+            {target_attr}="{target_value}"
+        />""".format(
+            id_attr=id_pair.name, id_value=id_pair.value,
+            category_attr=category_pair.name, category_value=category_pair.value,
+            target_attr=target_pair.name, target_value=target_pair.value,
+        )
+        node = etree.fromstring(xblock_xml)
+        definition_node = etree.fromstring(xblock_definition_xml)
+
+        patched_load_definition_xml.return_value = (definition_node, "irrelevant")
+
+        block = DiscussionXBlock.parse_xml(node, self.runtime_mock, self.keys, self.id_gen_mock)
+        try:
+            assert block.discussion_id == id_pair.value
+            assert block.discussion_category == category_pair.value
+            assert block.discussion_target == target_pair.value
+        except AssertionError:
+            print(xblock_xml, xblock_definition_xml)
+            raise
+
+    def test_export_default_discussion_id(self):
+        """
+        Test that default discussion_id values are not exported.
+
+        Historically, the OLX format allowed omitting discussion ID values; in such case, the IDs are generated
+        deterministically based on the course ID and the usage ID. Moreover, Studio does not allow course authors
+        to edit discussion_id, so all courses authored in Studio have discussion_id omitted in OLX.
+
+        Forcing Studio to always export discussion_id can cause data loss when switching between an older and newer
+        export,  in a course with a course ID different from the one from which the export was created - because the
+        discussion ID would be different.
+        """
+        target_node = etree.Element('dummy')
+
+        block = DiscussionXBlock(self.runtime_mock, scope_ids=self.keys, field_data=DictFieldData({}))
+        discussion_id_field = block.fields['discussion_id']  # pylint: disable=unsubscriptable-object
+
+        # precondition checks - discussion_id does not have a value and uses UNIQUE_ID
+        assert discussion_id_field._get_cached_value(block) == NO_CACHE_VALUE  # pylint: disable=W0212
+        assert discussion_id_field.default == UNIQUE_ID
+
+        block.add_xml_to_node(target_node)
+        assert target_node.tag == 'discussion'  # pylint: disable=W0212
+        assert 'discussion_id' not in target_node.attrib
+
+    @ddt.data("jediwannabe", "iddqd", "itisagooddaytodie")
+    def test_export_custom_discussion_id(self, discussion_id):
+        """
+        Test that custom discussion_id values are exported
+        """
+        target_node = etree.Element('dummy')
+
+        block = DiscussionXBlock(self.runtime_mock, scope_ids=self.keys, field_data=DictFieldData({}))
+        block.discussion_id = discussion_id
+
+        # precondition check
+        assert block.discussion_id == discussion_id
+
+        block.add_xml_to_node(target_node)
+        assert target_node.tag == 'discussion'
+        assert target_node.attrib['discussion_id'], discussion_id