Support the PEP 479pep479

4 files changed, 82 insertions, 41 deletions

diff --git a/doc/changelog.rst b/doc/changelog.rst
index 51d4d2e..9679a71 100644
--- a/doc/changelog.rst
+++ b/doc/changelog.rst
@@ -14,6 +14,9 @@ Changes:
   functions. Patch by Donald Stufft.
 * Add run_aiotest.py: run the aiotest test suite.
 * tox now also run the aiotest test suite
+* On Python 3.3 and newer, Return now also logs an error when used without
+  raise.
+* Support Python 3.5 with the PEP 479.
 
 Bugfixes:
 
diff --git a/tests/test_tasks.py b/tests/test_tasks.py
index e1a8a27..6d04c4f 100644
--- a/tests/test_tasks.py
+++ b/tests/test_tasks.py
@@ -1585,7 +1585,7 @@ class TaskTests(test_utils.TestCase):
             cw.send(None)
             try:
                 cw.send(arg)
-            except StopIteration as ex:
+            except Return as ex:
                 ex.raised = True
                 return ex.value
             else:
diff --git a/trollius/coroutines.py b/trollius/coroutines.py
index 650bc13..81a44f6 100644
--- a/trollius/coroutines.py
+++ b/trollius/coroutines.py
@@ -6,6 +6,7 @@ import inspect
 import opcode
 import os
 import sys
+import textwrap
 import traceback
 import types
 
@@ -59,51 +60,34 @@ else:
     _YIELD_FROM_BUG = False
 
 
-if compat.PY33:
-    # Don't use the Return class on Python 3.3 and later to support asyncio
-    # coroutines (to avoid the warning emited in Return destructor).
-    #
-    # The problem is that Return inherits from StopIteration.  "yield from
-    # trollius_coroutine". Task._step() does not receive the Return exception,
-    # because "yield from" handles it internally. So it's not possible to set
-    # the raised attribute to True to avoid the warning in Return destructor.
-    def Return(*args):
+class Return(Exception):
+    def __init__(self, *args):
+        Exception.__init__(self)
         if not args:
-            value = None
+            self.value = None
         elif len(args) == 1:
-            value = args[0]
+            self.value = args[0]
         else:
-            value = args
-        return StopIteration(value)
-else:
-    class Return(StopIteration):
-        def __init__(self, *args):
-            StopIteration.__init__(self)
-            if not args:
-                self.value = None
-            elif len(args) == 1:
-                self.value = args[0]
-            else:
-                self.value = args
-            self.raised = False
-            if _DEBUG:
-                frame = sys._getframe(1)
-                self._source_traceback = traceback.extract_stack(frame)
-                # explicitly clear the reference to avoid reference cycles
-                frame = None
-            else:
-                self._source_traceback = None
+            self.value = args
+        self.raised = False
+        if _DEBUG:
+            frame = sys._getframe(1)
+            self._source_traceback = traceback.extract_stack(frame)
+            # explicitly clear the reference to avoid reference cycles
+            frame = None
+        else:
+            self._source_traceback = None
 
-        def __del__(self):
-            if self.raised:
-                return
+    def __del__(self):
+        if self.raised:
+            return
 
-            fmt = 'Return(%r) used without raise'
-            if self._source_traceback:
-                fmt += '\nReturn created at (most recent call last):\n'
-                tb = ''.join(traceback.format_list(self._source_traceback))
-                fmt += tb.rstrip()
-            logger.error(fmt, self.value)
+        fmt = 'Return(%r) used without raise'
+        if self._source_traceback:
+            fmt += '\nReturn created at (most recent call last):\n'
+            tb = ''.join(traceback.format_list(self._source_traceback))
+            fmt += tb.rstrip()
+        logger.error(fmt, self.value)
 
 
 def _coroutine_at_yield_from(coro):
@@ -245,6 +229,48 @@ if not compat.PY34:
 else:
     _wraps = functools.wraps
 
+_PEP479 = (sys.version_info >= (3,))
+if _PEP479:
+    exec(textwrap.dedent('''
+        def pep479_wrapper(func, coro_func):
+            @_wraps(func)
+            def pep479_wrapped(*args, **kw):
+                coro = coro_func(*args, **kw)
+                value = None
+                error = None
+                while True:
+                    try:
+                        if error is not None:
+                            value = coro.throw(error)
+                        elif value is not None:
+                            value = coro.send(value)
+                        else:
+                            value = next(coro)
+                    except RuntimeError as exc:
+                        if isinstance(exc.__context__, StopIteration):
+                            # a trollius coroutine uses "raise Return"
+                            raise
+                            return exc.__context__.value
+                        else:
+                            raise
+                    except StopIteration as exc:
+                        return exc.value
+                    except Return as exc:
+                        exc.raised = True
+                        return exc.value
+                    except BaseException as exc:
+                        raise
+
+                    try:
+                        value = yield value
+                        error = None
+                    except BaseException as exc:
+                        value = None
+                        error = exc
+            return pep479_wrapped
+        '''))
+
+
 def coroutine(func):
     """Decorator to mark coroutines.
 
@@ -262,6 +288,11 @@ def coroutine(func):
                 res = yield From(res)
             raise Return(res)
 
+    if _PEP479:
+        # FIXME: use @_wraps
+        coro = pep479_wrapper(func, coro)
+        coro = _wraps(func)(coro)
+
     if not _DEBUG:
         wrapper = coro
     else:
diff --git a/trollius/tasks.py b/trollius/tasks.py
index 4d91de8..ec34f58 100644
--- a/trollius/tasks.py
+++ b/trollius/tasks.py
@@ -253,6 +253,13 @@ class Task(futures.Future):
                 result = coro.send(value)
             else:
                 result = next(coro)
+        except coroutines.Return as exc:
+            if isinstance(exc, Return):
+                exc.raised = True
+                result = exc.value
+            else:
+                result = None
+            self.set_result(result)
         except StopIteration as exc:
             if compat.PY33:
                 # asyncio Task object? get the result of the coroutine