Adds add_field_to_json to utils.py

It also adds the corresponding unit test

Author: pvelasco

heudiconv/tests/test_utils.py

@@ -10,6 +10,7 @@
     load_json,
     create_tree,
     save_json,
+    add_field_to_json,
     get_datetime,
     JSONDecodeError)
 
@@ -88,6 +89,32 @@ def test_load_json(tmpdir, caplog):
     assert load_json(valid_json_file) == vcontent
 
 
+def test_add_field_to_json(tmpdir):
+    """
+    Test utils.add_field_to_json()
+    """
+    dummy_json_file = str(tmpdir / 'dummy.json')
+    some_content = {"name": "Jason", "age": 30, "city": "New York"}
+    save_json(dummy_json_file, some_content, pretty=True)
+
+    added_content = {"LastName": "Bourne",
+                     "Movies": [
+                         "The Bourne Identity",
+                         "The Bourne Supremacy",
+                         "The Bourne Ultimatum",
+                         "The Bourne Legacy",
+                         "Jason Bourne"
+                     ]
+                     }
+    add_field_to_json(dummy_json_file, added_content)
+
+    # check that it was added:
+    with open(dummy_json_file) as f:
+        data = json.load(f)
+    some_content.update(added_content)
+    assert data == some_content
+
+
 def test_get_datetime():
     """
     Test utils.get_datetime()

heudiconv/utils.py

@@ -264,6 +264,32 @@ def json_dumps_pretty(j, indent=2, sort_keys=True):
     return js_
 
 
+def add_field_to_json(json_file, field_and_value):
+    """
+    Adds a given field (and its value) to a json file
+
+    Parameters:
+    -----------
+    json_file : str or Path
+        path for the corresponding json file
+    field_and_value : dict
+        pair of "key": "value" to add to the json file
+    """
+    for key, value in field_and_value.items():
+        lgr.debug(
+            'File: "{f}": Adding {k}: {v}'.format(
+                f=json_file,
+                k=key,
+                v=value,
+            )
+        )
+
+    with open(json_file) as f:
+        data = json.load(f)
+    data.update(field_and_value)
+    save_json(json_file, data, pretty=True)
+
+
 def treat_infofile(filename):
     """Tune up generated .json file (slim down, pretty-print for humans).
     """