Warning for links (#891)

* warning:

* Update CHANGELOG.md

* Update src/hdmf/container.py

Co-authored-by: Oliver Ruebel <oruebel@users.noreply.github.com>

* Update CHANGELOG.md

---------

Co-authored-by: Oliver Ruebel <oruebel@users.noreply.github.com>

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### New features and minor improvements
 - Updated `ExternalResources` to have EntityKeyTable with updated tests/documentation and minor bug fix to ObjectKeyTable. @mavaylon1 [#872](https://github.com/hdmf-dev/hdmf/pull/872)
+- Added warning for DynamicTableRegion links that are not added to the same parent as the original container object. @mavaylon1 [#891](https://github.com/hdmf-dev/hdmf/pull/891)
 
 ## HMDF 3.6.1 (May 18, 2023)
 

src/hdmf/container.py

@@ -354,6 +354,13 @@ def parent(self, parent_container):
             if isinstance(parent_container, Container):
                 parent_container.__children.append(self)
                 parent_container.set_modified()
+            for child in self.children:
+                if type(child).__name__ == "DynamicTableRegion":
+                    if child.table.parent is None:
+                        msg = "The table for this DynamicTableRegion has not been added to the parent."
+                        warn(msg)
+                    else:
+                        continue
 
     def _remove_child(self, child):
         """Remove a child Container. Intended for use in subclasses that allow dynamic addition of child Containers."""

tests/unit/test_container.py

@@ -5,6 +5,7 @@
 from hdmf.common.resources import ExternalResources
 from hdmf.testing import TestCase
 from hdmf.utils import docval
+from hdmf.common import (DynamicTable, VectorData, DynamicTableRegion)
 
 
 class Subcontainer(Container):
@@ -136,6 +137,47 @@ def test_add_child(self):
         self.assertTrue(parent_obj.modified)
         self.assertIs(parent_obj.children[0], child_obj)
 
+    def test_parent_set_link_warning(self):
+        col1 = VectorData(
+            name='col1',
+            description='column #1',
+            data=[1, 2],
+        )
+        col2 = VectorData(
+            name='col2',
+            description='column #2',
+            data=['a', 'b'],
+        )
+
+        # this table will have two rows with ids 0 and 1
+        table = DynamicTable(
+            name='my table',
+            description='an example table',
+            columns=[col1, col2],
+        )
+
+        dtr_col = DynamicTableRegion(
+            name='table1_ref',
+            description='references rows of earlier table',
+            data=[0, 1, 0, 0],  # refers to row indices of the 'table' variable
+            table=table
+        )
+
+        data_col = VectorData(
+            name='col2',
+            description='column #2',
+            data=['a', 'a', 'a', 'b'],
+        )
+
+        table2 = DynamicTable(
+            name='my_table',
+            description='an example table',
+            columns=[dtr_col, data_col],
+        )
+
+        with self.assertWarns(Warning):
+            table2.parent=ContainerWithChild()
+
     def test_set_parent_exists(self):
         """Test that setting a parent a second time does nothing
         """