fix #795: Making tf_util._Function consistent (#796)

* fix #795: Making tf_util._Function consistent

The fix involves using the placeholder name to crossreference passed
kwargs values, just like the tf_util.function expects. Also, the givens
are updated before the parameters to make it behave like it's supposed
to.

* test: Adding test for issue #795

baselines/common/tests/test_tf_util.py

@@ -18,7 +18,9 @@ def test_function():
             initialize()
 
             assert lin(2) == 6
+            assert lin(x=3) == 9
             assert lin(2, 2) == 10
+            assert lin(x=2, y=3) == 12
 
 
 def test_multikwargs():

baselines/common/tf_util.py

@@ -186,6 +186,7 @@ class _Function(object):
             if not hasattr(inpt, 'make_feed_dict') and not (type(inpt) is tf.Tensor and len(inpt.op.inputs) == 0):
                 assert False, "inputs should all be placeholders, constants, or have a make_feed_dict method"
         self.inputs = inputs
+        self.input_names = {inp.name.split("/")[-1].split(":")[0]: inp for inp in inputs}
         updates = updates or []
         self.update_group = tf.group(*updates)
         self.outputs_update = list(outputs) + [self.update_group]
@@ -197,15 +198,17 @@ class _Function(object):
         else:
             feed_dict[inpt] = adjust_shape(inpt, value)
 
-    def __call__(self, *args):
-        assert len(args) <= len(self.inputs), "Too many arguments provided"
+    def __call__(self, *args, **kwargs):
+        assert len(args) + len(kwargs) <= len(self.inputs), "Too many arguments provided"
         feed_dict = {}
-        # Update the args
-        for inpt, value in zip(self.inputs, args):
-            self._feed_input(feed_dict, inpt, value)
         # Update feed dict with givens.
         for inpt in self.givens:
             feed_dict[inpt] = adjust_shape(inpt, feed_dict.get(inpt, self.givens[inpt]))
+        # Update the args
+        for inpt, value in zip(self.inputs, args):
+            self._feed_input(feed_dict, inpt, value)
+        for inpt_name, value in kwargs.items():
+            self._feed_input(feed_dict, self.input_names[inpt_name], value)
         results = get_session().run(self.outputs_update, feed_dict=feed_dict)[:-1]
         return results