contextlib: modify ExitStack to work in uPy

contextlib/contextlib.py

@@ -4,7 +4,6 @@ Original source code: https://hg.python.org/cpython/file/3.4/Lib/contextlib.py
 
 Not implemented:
  - redirect_stdout;
- - ExitStack.
 
 """
 
@@ -94,7 +93,6 @@ class ExitStack(object):
         """Helper to correctly register callbacks to __exit__ methods"""
         def _exit_wrapper(*exc_details):
             return cm_exit(cm, *exc_details)
-        _exit_wrapper.__self__ = cm
         self.push(_exit_wrapper)
 
     def push(self, exit):
@@ -124,9 +122,6 @@ class ExitStack(object):
         """
         def _exit_wrapper(exc_type, exc, tb):
             callback(*args, **kwds)
-        # We changed the signature, so using @wraps is not appropriate, but
-        # setting __wrapped__ may still help with introspection
-        _exit_wrapper.__wrapped__ = callback
         self.push(_exit_wrapper)
         return callback # Allow use as a decorator
 
@@ -152,24 +147,6 @@ class ExitStack(object):
 
     def __exit__(self, *exc_details):
         received_exc = exc_details[0] is not None
-
-        # We manipulate the exception state so it behaves as though
-        # we were actually nesting multiple with statements
-        frame_exc = sys.exc_info()[1]
-        def _fix_exception_context(new_exc, old_exc):
-            # Context may not be correct, so find the end of the chain
-            while 1:
-                exc_context = new_exc.__context__
-                if exc_context is old_exc:
-                    # Context is already set correctly (see issue 20317)
-                    return
-                if exc_context is None or exc_context is frame_exc:
-                    break
-                new_exc = exc_context
-            # Change the end of the chain to point to the exception
-            # we expect it to reference
-            new_exc.__context__ = old_exc
-
         # Callbacks are invoked in LIFO order to match the behaviour of
         # nested context managers
         suppressed_exc = False
@@ -182,18 +159,8 @@ class ExitStack(object):
                     pending_raise = False
                     exc_details = (None, None, None)
             except:
-                new_exc_details = sys.exc_info()
-                # simulate the stack of exceptions by setting the context
-                _fix_exception_context(new_exc_details[1], exc_details[1])
+                exc_details = sys.exc_info()
                 pending_raise = True
-                exc_details = new_exc_details
         if pending_raise:
-            try:
-                # bare "raise exc_details[1]" replaces our carefully
-                # set-up context
-                fixed_ctx = exc_details[1].__context__
-                raise exc_details[1]
-            except BaseException:
-                exc_details[1].__context__ = fixed_ctx
-                raise
+            raise exc_details[1]
         return received_exc and suppressed_exc

contextlib/metadata.txt

@@ -1,5 +1,5 @@
 srctype = cpython
 type = module
-version = 3.4.2-2
+version = 3.4.2-3
 long_desc = Port of contextlib for micropython
-depends = ucontextlib
+depends = ucontextlib, collections

contextlib/setup.py

@@ -6,7 +6,7 @@ from setuptools import setup
 
 
 setup(name='micropython-contextlib',
-      version='3.4.2-2',
+      version='3.4.2-3',
       description='CPython contextlib module ported to MicroPython',
       long_description='This is a module ported from CPython standard library to be compatible with\nMicroPython interpreter. Usually, this means applying small patches for\nfeatures not supported (yet, or at all) in MicroPython. Sometimes, heavier\nchanges are required. Note that CPython modules are written with availability\nof vast resources in mind, and may not work for MicroPython ports with\nlimited heap. If you are affected by such a case, please help reimplement\nthe module from scratch.',
       url='https://github.com/micropython/micropython/issues/405',
@@ -16,4 +16,4 @@ setup(name='micropython-contextlib',
       maintainer_email='micro-python@googlegroups.com',
       license='Python',
       py_modules=['contextlib'],
-      install_requires=['micropython-ucontextlib'])
+      install_requires=['micropython-ucontextlib', 'micropython-collections'])