Conver APIListDataSource to use Future.Then() rather than Get().

chrome/common/extensions/docs/server2/future_test.py

 #!/usr/bin/env python
 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import traceback
 import unittest
 
 
 from future import All, Future, Race
@@ skipping 143 matching lines @@
                  except_pass=(NotImplementedError,))
     self.assertRaises(ValueError, race.Get)
 
     race = Race((Future(callback=throws_error),
                  Future(callback=throws_error)),
                  except_pass=(ValueError,))
     self.assertRaises(ValueError, race.Get)
 
   def testThen(self):
     def assertIs42(val):
-      self.assertEquals(val, 42)
+      self.assertEqual(val, 42)
+      return val
 
     then = Future(value=42).Then(assertIs42)
     # Shouldn't raise an error.
-    then.Get()
+    self.assertEqual(42, then.Get())
 
     # Test raising an error.
     then = Future(value=41).Then(assertIs42)
     self.assertRaises(AssertionError, then.Get)
 
     # Test setting up an error handler.
     def handle(error):
       if isinstance(error, ValueError):
         return 'Caught'
       raise error
 
     def raiseValueError():
       raise ValueError
 
     def raiseException():
       raise Exception
 
     then = Future(callback=raiseValueError).Then(assertIs42, handle)
-    self.assertEquals(then.Get(), 'Caught')
+    self.assertEqual('Caught', then.Get())
     then = Future(callback=raiseException).Then(assertIs42, handle)
     self.assertRaises(Exception, then.Get)
 
     # Test chains of thens.
     addOne = lambda val: val + 1
     then = Future(value=40).Then(addOne).Then(addOne).Then(assertIs42)
     # Shouldn't raise an error.
-    then.Get()
+    self.assertEqual(42, then.Get())
 
     # Test error in chain.
     then = Future(value=40).Then(addOne).Then(assertIs42).Then(addOne)
     self.assertRaises(AssertionError, then.Get)
 
     # Test handle error in chain.
     def raiseValueErrorWithVal(val):
       raise ValueError
 
     then = Future(value=40).Then(addOne).Then(raiseValueErrorWithVal).Then(
         addOne, handle).Then(lambda val: val + ' me')
     self.assertEquals(then.Get(), 'Caught me')
 
     # Test multiple handlers.
     def myHandle(error):
       if isinstance(error, AssertionError):
         return 10
       raise error
 
     then = Future(value=40).Then(assertIs42).Then(addOne, handle).Then(addOne,
                                                                        myHandle)
     self.assertEquals(then.Get(), 10)
 
+  def testThenResolvesReturnedFutures(self):
+    def returnsFortyTwo():
+      return Future(value=42)
+    def inc(x):
+      return x + 1
+    def incFuture(x):
+      return Future(value=x + 1)
+
+    self.assertEqual(43, returnsFortyTwo().Then(inc).Get())
+    self.assertEqual(43, returnsFortyTwo().Then(incFuture).Get())
+    self.assertEqual(44, returnsFortyTwo().Then(inc).Then(inc).Get())
+    self.assertEqual(44, returnsFortyTwo().Then(inc).Then(incFuture).Get())
+    self.assertEqual(44, returnsFortyTwo().Then(incFuture).Then(inc).Get())
+    self.assertEqual(
+        44, returnsFortyTwo().Then(incFuture).Then(incFuture).Get())
+
+    # The same behaviour should apply to error handlers.
+    def raisesSomething():
+      def boom(): raise ValueError
+      return Future(callback=boom)
+    def shouldNotHappen(_):
+      raise AssertionError()
+    def oops(error):
+      return 'oops'
+    def oopsFuture(error):
+      return Future(value='oops')
+
+    self.assertEqual(
+        'oops', raisesSomething().Then(shouldNotHappen, oops).Get())
+    self.assertEqual(
+        'oops', raisesSomething().Then(shouldNotHappen, oopsFuture).Get())
+    self.assertEqual(
+        'oops',
+        raisesSomething().Then(shouldNotHappen, raisesSomething)
+                         .Then(shouldNotHappen, oops).Get())
+    self.assertEqual(
+        'oops',
+        raisesSomething().Then(shouldNotHappen, raisesSomething)
+                         .Then(shouldNotHappen, oopsFuture).Get())
+
 
 if __name__ == '__main__':
   unittest.main()