fields: make it possible to prefill with a date object (#13787)

tests/test_prefill.py

@@ -1,3 +1,4 @@
+import datetime
 import sys
 import shutil
 
@@ -86,3 +87,13 @@ def test_prefill_formula_substitution_variable():
     field = fields.Field()
     field.prefill = {'type': 'formula', 'value': 'test'}
     assert field.get_prefill_value() == ('value', False)
+
+def test_prefill_formula_date_value():
+    pub.substitutions.get_context_variables = lambda: {}
+    field = fields.Field()
+    field.prefill = {'type': 'formula', 'value': 'utils.add_days(utils.today(), 10)'}
+    in_ten_days = (datetime.date.today() + datetime.timedelta(days=10)).strftime('%Y-%m-%d')
+    assert field.get_prefill_value() == (in_ten_days, False)
+
+    field.prefill = {'type': 'formula', 'value': 'utils.add_days("2016-01-01", 10)'}
+    assert field.get_prefill_value() == ('2016-01-11', False)

wcs/fields.py

@@ -14,6 +14,7 @@
 # You should have received a copy of the GNU General Public License
 # along with this program; if not, see <http://www.gnu.org/licenses/>.
 
+import datetime
 import json
 import time
 import random
@@ -301,6 +302,8 @@ class Field(object):
                 ret = eval(formula,
                     get_publisher().get_global_eval_dict(),
                     get_publisher().substitutions.get_context_variables())
+                if isinstance(ret, datetime.date):
+                    ret = ret.strftime(date_format())
                 if ret:
                     return (str(ret), False)
             except: