[FLINK-37457][python] Support asArgument in Python Table API

Author: autophagy

flink-python/docs/reference/pyflink.table/expressions.rst

@@ -140,6 +140,7 @@ arithmetic functions
     Expression.collect
     Expression.array_agg
     Expression.alias
+    Expression.as_argument
     Expression.cast
     Expression.try_cast
     Expression.asc

flink-python/pyflink/table/expression.py

@@ -859,6 +859,31 @@ def alias(self, name: str, *extra_names: str) -> 'Expression[T]':
         gateway = get_gateway()
         return _ternary_op("as")(self, name, to_jarray(gateway.jvm.String, extra_names))
 
+    def as_argument(self, name: str) -> 'Expression':
+        """
+        Converts this expression into a named argument.
+
+        If the function declares a static signature (usually indicated by the "=>" assignment
+        operator), the framework is able to reorder named arguments and consider optional arguments
+        accordingly, before passing them into the function call.
+
+        .. note::
+            Not every function supports named arguments. Named arguments are not available for
+            signatures that are overloaded, use varargs, or any other kind of input type strategy.
+
+        Example:
+        ::
+
+            >>> table.select(
+            ...     call(
+            ...         "MyFunction",
+            ...         col("my_column").as_argument("input"),
+            ...         lit(42).as_argument("threshold")
+            ...     )
+            ... )
+        """
+        return _binary_op("asArgument")(self, name)
+
     def cast(self, data_type: DataType) -> 'Expression':
         """
         Returns a new value being cast to type type.

flink-python/pyflink/table/tests/test_expression.py

@@ -132,6 +132,8 @@ def test_expression(self):
         self.assertEqual('PERCENTILE(a, array(0.1, 0.5))', str(expr1.percentile(array(0.1, 0.5))))
         self.assertEqual('PERCENTILE(a, array(0.1, 0.5), b)',
                          str(expr1.percentile(array(0.1, 0.5), expr2)))
+        self.assertEqual("ASSIGNMENT('a2', a)", str(expr1.as_argument('a2')))
+        self.assertEqual("ASSIGNMENT('a', 10)", str(expr5.as_argument('a')))
 
         # string functions
         self.assertEqual('substring(a, b)', str(expr1.substring(expr2)))

flink-python/pyflink/table/tests/test_expression_completeness.py

@@ -58,7 +58,6 @@ def excluded_methods(cls):
             'times',
             'mod',
             'power',
-            'asArgument',
         }
 
     @classmethod