set_data_io method and associated test (#934)

* draft of set_data_io method and associated test

* improve test coverage

* Update CHANGELOG.md

Author: bendichter

CHANGELOG.md

@@ -9,6 +9,7 @@
 - Added the magic `__reduce__` method as well as two private semi-abstract helper methods to enable pickling of the `GenericDataChunkIterator`. @codycbakerphd [#924](https://github.com/hdmf-dev/hdmf/pull/924)
 - Added Dynamic Enumerations and Schemasheets support to `TermSet`. @mavaylon1 [#923](https://github.com/hdmf-dev/hdmf/pull/923)
 - Updated `HERD` to support user defined file name for the `HERD` zip file. @mavaylon1 [#941](https://github.com/hdmf-dev/hdmf/pull/941)
+- Added method `Containter.set_data_io`, which wraps an existing data field in a `DataIO`. @bendichter [#938](https://github.com/hdmf-dev/hdmf/pull/938)
 
 ## HDMF 3.8.1 (July 25, 2023)
 

src/hdmf/container.py

@@ -708,6 +708,12 @@ def __smart_str_dict(d, num_indent):
         out += '\n' + indent + right_br
         return out
 
+    def set_data_io(self, dataset_name, data_io_class, **kwargs):
+        data = self.fields.get(dataset_name)
+        if data is None:
+            raise ValueError(f"{dataset_name} is None and cannot be wrapped in a DataIO class")
+        self.fields[dataset_name] = data_io_class(data=data, **kwargs)
+
 
 class Data(AbstractContainer):
     """

tests/unit/test_container.py

@@ -2,6 +2,7 @@
 from uuid import uuid4, UUID
 import os
 
+from hdmf.backends.hdf5 import H5DataIO
 from hdmf.container import AbstractContainer, Container, Data, HERDManager
 from hdmf.common.resources import HERD
 from hdmf.testing import TestCase
@@ -394,6 +395,29 @@ def test_get_ancestors(self):
         self.assertTupleEqual(parent_obj.get_ancestors(), (grandparent_obj, ))
         self.assertTupleEqual(child_obj.get_ancestors(), (parent_obj, grandparent_obj))
 
+    def test_set_data_io(self):
+
+        class ContainerWithData(Container):
+            __fields__ = ('data1', 'data2')
+
+            @docval(
+                {"name": "name", "doc": "name", "type": str},
+                {'name': 'data1', 'doc': 'field1 doc', 'type': list},
+                {'name': 'data2', 'doc': 'field2 doc', 'type':  list, 'default': None}
+            )
+            def __init__(self, **kwargs):
+                super().__init__(name=kwargs["name"])
+                self.data1 = kwargs["data1"]
+                self.data2 = kwargs["data2"]
+
+        obj = ContainerWithData("name", [1, 2, 3, 4, 5], None)
+        obj.set_data_io("data1", H5DataIO, chunks=True)
+        assert isinstance(obj.data1, H5DataIO)
+
+        with self.assertRaises(ValueError):
+            obj.set_data_io("data2", H5DataIO, chunks=True)
+
+
 
 class TestHTMLRepr(TestCase):