Allow optional *args with base AnsiFunction

Amended the :class:`.AnsiFunction` class, the base of common SQL
functions like ``CURRENT_TIMESTAMP``, to accept positional arguments
like a regular ad-hoc function.  This to suit the case that many of
these functions on specific backends accept arguments such as
"fractional seconds" precision and such.  If the function is created
with arguments, it renders the the parenthesis and the arguments.  If
no arguents are present, the compiler generates the non-parenthesized form.

Fixes: #4386
Change-Id: Ic492ef177e4987cec99ec4d95f55292be8daa087

1 files changed, 11 insertions, 4 deletions

diff --git a/lib/sqlalchemy/sql/functions.py b/lib/sqlalchemy/sql/functions.py
index 5cea7750a..4b4d2d463 100644
--- a/lib/sqlalchemy/sql/functions.py
+++ b/lib/sqlalchemy/sql/functions.py
@@ -54,10 +54,13 @@ class FunctionElement(Executable, ColumnElement, FromClause):
 
     packagenames = ()
 
+    _has_args = False
+
     def __init__(self, *clauses, **kwargs):
         """Construct a :class:`.FunctionElement`.
         """
         args = [_literal_as_binds(c, self.name) for c in clauses]
+        self._has_args = self._has_args or bool(args)
         self.clause_expr = ClauseList(
             operator=operators.comma_op,
             group_contents=True, *args).\
@@ -635,6 +638,7 @@ class GenericFunction(util.with_metaclass(_GenericMeta, Function)):
         parsed_args = kwargs.pop('_parsed_args', None)
         if parsed_args is None:
             parsed_args = [_literal_as_binds(c, self.name) for c in args]
+        self._has_args = self._has_args or bool(parsed_args)
         self.packagenames = []
         self._bind = kwargs.get('bind', None)
         self.clause_expr = ClauseList(
@@ -671,8 +675,8 @@ class next_value(GenericFunction):
 
 
 class AnsiFunction(GenericFunction):
-    def __init__(self, **kwargs):
-        GenericFunction.__init__(self, **kwargs)
+    def __init__(self, *args, **kwargs):
+        GenericFunction.__init__(self, *args, **kwargs)
 
 
 class ReturnTypeFromArgs(GenericFunction):
@@ -686,7 +690,7 @@ class ReturnTypeFromArgs(GenericFunction):
 
 
 class coalesce(ReturnTypeFromArgs):
-    pass
+    _has_args = True
 
 
 class max(ReturnTypeFromArgs):
@@ -717,7 +721,7 @@ class char_length(GenericFunction):
 
 
 class random(GenericFunction):
-    pass
+    _has_args = True
 
 
 class count(GenericFunction):
@@ -937,6 +941,7 @@ class cube(GenericFunction):
     .. versionadded:: 1.2
 
     """
+    _has_args = True
 
 
 class rollup(GenericFunction):
@@ -952,6 +957,7 @@ class rollup(GenericFunction):
     .. versionadded:: 1.2
 
     """
+    _has_args = True
 
 
 class grouping_sets(GenericFunction):
@@ -984,3 +990,4 @@ class grouping_sets(GenericFunction):
     .. versionadded:: 1.2
 
     """
+    _has_args = True