templatetags: correct decimal filter output on 0 (#30770)

tests/test_templates.py

@@ -292,6 +292,7 @@ def test_decimal_templatetag():
     assert tmpl.render({'plop': 3.14}) == '3.14'
     assert tmpl.render({'plop': 12345.678}) == '12345.678'
     assert tmpl.render({'plop': None}) == ''
+    assert tmpl.render({'plop': 0}) == '0'
 
     tmpl = Template('{{ plop|decimal:3 }}')
     assert tmpl.render({'plop': '3.14'}) == '3.140'

wcs/qommon/templatetags/qommon.py

@@ -112,8 +112,6 @@ def time(value, arg=None):
     return defaultfilters.date(value, arg=arg)
 
 def parse_decimal(value):
-    if not value:
-        return None
     if isinstance(value, basestring):
         # replace , by . for French users comfort
         value = value.replace(',', '.')
@@ -124,10 +122,12 @@ def parse_decimal(value):
 
 @register.filter(is_safe=False)
 def decimal(value, arg=None):
-    if arg is None:
-        return parse_decimal(value) or ''
     if not isinstance(value, Decimal):
         value = parse_decimal(value)
+    if value is None:
+        return ''
+    if arg is None:
+        return value
     return defaultfilters.floatformat(value, arg=arg)
 
 @register.filter(expects_localtime=True, is_safe=False)