fix json dump, add tests to check overwrite

Author: oesteban

nipype/interfaces/base.py

@@ -48,6 +48,7 @@
 iflogger = logging.getLogger('interface')
 
 PY35 = sys.version_info >= (3, 5)
+PY3 = sys.version_info[0] > 2
 
 if runtime_profile:
     try:
@@ -1197,8 +1198,8 @@ def save_inputs_to_json(self, json_file):
         """
         inputs = self.inputs.get_traitsfree()
         iflogger.debug('saving inputs {}', inputs)
-        with open(json_file, 'w') as fhandle:
-            json.dump(inputs, fhandle, indent=4)
+        with open(json_file, 'w' if PY3 else 'wb') as fhandle:
+            json.dump(inputs, fhandle, indent=4, ensure_ascii=False)
 
 
 class Stream(object):

nipype/interfaces/tests/test_base.py

@@ -461,12 +461,6 @@ def test_BaseInterface_load_save_inputs():
     tmp_dir = tempfile.mkdtemp()
     tmp_json = os.path.join(tmp_dir, 'settings.json')
 
-    def _rem_undefined(indict):
-        for key, val in list(indict.items()):
-            if not nib.isdefined(val):
-                indict.pop(key, None)
-        return indict
-
     class InputSpec(nib.TraitedSpec):
         input1 = nib.traits.Int()
         input2 = nib.traits.Float()
@@ -485,14 +479,23 @@ def __init__(self, **inputs):
     bif.save_inputs_to_json(tmp_json)
     bif2 = DerivedInterface()
     bif2.load_inputs_from_json(tmp_json)
-    yield assert_equal, _rem_undefined(bif2.inputs.get()), inputs_dict
+    yield assert_equal, bif2.inputs.get_traitsfree(), inputs_dict
 
     bif3 = DerivedInterface(from_file=tmp_json)
-    yield assert_equal, _rem_undefined(bif3.inputs.get()), inputs_dict
+    yield assert_equal, bif3.inputs.get_traitsfree(), inputs_dict
+
+    inputs_dict2 = inputs_dict.copy()
+    inputs_dict2.update({'input4': 'some other string'})
+    bif4 = DerivedInterface(from_file=tmp_json, input4=inputs_dict2['input4'])
+    yield assert_equal, bif4.inputs.get_traitsfree(), inputs_dict2
+
+    bif5 = DerivedInterface(input4=inputs_dict2['input4'])
+    bif5.load_inputs_from_json(tmp_json, overwrite=False)
+    yield assert_equal, bif5.inputs.get_traitsfree(), inputs_dict2
 
-    inputs_dict.update({'input4': 'some other string'})
-    bif4 = DerivedInterface(from_file=tmp_json, input4='some other string')
-    yield assert_equal, _rem_undefined(bif4.inputs.get()), inputs_dict
+    bif6 = DerivedInterface(input4=inputs_dict2['input4'])
+    bif6.load_inputs_from_json(tmp_json)
+    yield assert_equal, bif6.inputs.get_traitsfree(), inputs_dict
 
 def assert_not_raises(fn, *args, **kwargs):
     fn(*args, **kwargs)