add recursive string type for arrays of arbitrary dim

src/hdmf/build/objectmapper.py

@@ -598,11 +598,17 @@ def __get_data_type(cls, spec):
 
     def __convert_string(self, value, spec):
         """Convert string types to the specified dtype."""
+        def __apply_string_type(value, string_type):
+            if isinstance(value, (list, tuple, np.ndarray, DataIO)):
+                return [__apply_string_type(item, string_type) for item in value]
+            else:
+                return string_type(value)
+
         ret = value
         if isinstance(spec, AttributeSpec):
             if 'text' in spec.dtype:
                 if spec.shape is not None or spec.dims is not None:
-                    ret = list(map(str, value))
+                    ret = __apply_string_type(value, str)
                 else:
                     ret = str(value)
         elif isinstance(spec, DatasetSpec):
@@ -617,10 +623,8 @@ def __convert_string(self, value, spec):
                     def string_type(x):
                         return x.isoformat()  # method works for both date and datetime
                 if string_type is not None:
-                    if spec.shape is not None and len(spec.shape) > 1:
-                        ret = [[string_type(item) for item in sublist] for sublist in value]
-                    elif spec.shape is not None or spec.dims is not None:
-                        ret = list(map(string_type, value))
+                    if spec.shape is not None or spec.dims is not None:
+                        ret = __apply_string_type(value, string_type)
                     else:
                         ret = string_type(value)
                     # copy over any I/O parameters if they were specified