Handle self argument in defun.

PiperOrigin-RevId: 207646738

tensorflow/python/eager/function.py

@@ -960,11 +960,17 @@ def __init__(self,
     self._lock = threading.Lock()
 
     fullargspec = tf_inspect.getfullargspec(self._python_function)
+    if tf_inspect.ismethod(self._python_function):
+      # Remove `self`: default arguments shouldn't be matched to it.
+      args = fullargspec.args[1:]
+    else:
+      args = fullargspec.args
+
     # A cache mapping from argument name to index, for canonicalizing
     # arguments that are called in a keyword-like fashion.
-    self._args_to_indices = {arg: i for i, arg in enumerate(fullargspec.args)}
+    self._args_to_indices = {arg: i for i, arg in enumerate(args)}
     # A cache mapping from arg index to default value, for canonicalization.
-    offset = len(fullargspec.args) - len(fullargspec.defaults or [])
+    offset = len(args) - len(fullargspec.defaults or [])
     self._arg_indices_to_default_values = {
         offset + index: default
         for index, default in enumerate(fullargspec.defaults or [])

tensorflow/python/eager/function_test.py

@@ -1233,6 +1233,19 @@ def two(self, tensor, other=integer):
     self.assertEqual(one.numpy(), 1.0)
     self.assertEqual(two.numpy(), 2)
 
+  def testDefuningInstanceMethodWithDefaultArgument(self):
+
+    integer = constant_op.constant(2, dtypes.int64)
+
+    class Foo(object):
+
+      @function.defun
+      def func(self, other=integer):
+        return other
+
+    foo = Foo()
+    self.assertEqual(foo.func().numpy(), int(integer))
+
   def testPythonCallWithSideEffects(self):
     state = []