Fix TestCase.update() handling of unspecified fields. Fixes #1318

this still allows the API caller to specify only the fields which
they want to modify but properly initializes the rest of the values
based on the current object instance instead of reseting them
to None.

tcms/rpc/api/forms/testcase.py

@@ -27,4 +27,6 @@ def __init__(self, data=None, files=None, auto_id='id_%s', prefix=None,
         )
 
         for field in self.fields:
-            self.fields[field].required = False
+            # will cause BaseForm._clean_fields() to reuse the value
+            # from self.initial (<-- self.instance) if not specified
+            self.fields[field].disabled = field not in data

tcms/rpc/api/testcase.py

@@ -328,13 +328,6 @@ def update(case_id, values):
         :raises: PermissionDenied if missing *testcases.change_testcase* permission
     """
     test_case = TestCase.objects.get(pk=case_id)
-
-    # initialize mandatory values for FK fields if they are
-    # not specified by the caller
-    for fk_field in ('author', 'case_status', 'category', 'priority'):
-        if not (values.get(fk_field) or values.get(fk_field + '_id')):
-            values[fk_field] = getattr(test_case, fk_field + '_id')
-
     form = UpdateForm(values, instance=test_case)
 
     if form.is_valid():