Adds the simpleEnum class back. (#246)

* Adds its meta class back without using six.
* Adds unit tests back
* Adds a deprecation warning for the classes.

amazon/ion/util.py

@@ -17,10 +17,12 @@
 import sys
 
 from collections import namedtuple
+from warnings import warn
 
 
 class _RecordMetaClass(type):
     """Metaclass for defining named-tuple based immutable record types."""
+
     def __new__(cls, name, bases, attrs):
         if attrs.get('_record_sentinel') is None:
             field_declarations = []
@@ -78,6 +80,7 @@ class MyRecord(record('a', ('b', 1))):
     Args:
         fields (list[str | (str, any)]): A sequence of str or pairs that
     """
+
     class RecordType(object, metaclass=_RecordMetaClass):
         _record_sentinel = True
         _record_fields = fields
@@ -94,12 +97,14 @@ def coroutine(func):
     Returns:
         Callable: The decorated generator.
     """
+
     def wrapper(*args, **kwargs):
         gen = func(*args, **kwargs)
         val = next(gen)
         if val != None:
             raise TypeError('Unexpected value from start of coroutine')
         return gen
+
     wrapper.__name__ = func.__name__
     wrapper.__doc__ = func.__doc__
     return wrapper
@@ -142,6 +147,7 @@ class CodePoint(int):
     """Evaluates as the ordinal of a code point, while also containing the unicode character representation and
     indicating whether the code point was escaped.
     """
+
     def __init__(self, *args, **kwargs):
         self.char = None
         self.is_escaped = False
@@ -193,6 +199,7 @@ def combine_surrogates():
             real_code_point += (code_point - _HIGH_SURROGATE_START) << 10
             real_code_point += (low_code_point - _LOW_SURROGATE_START)
             return real_code_point, low_surrogate
+
         try:
             code_point, low = combine_surrogates()
         except StopIteration:
@@ -217,15 +224,110 @@ def bit_length(value):
             return 0
         return len(bin(abs(value))) - 2
 
+
     def total_seconds(td):
         return (td.microseconds + (td.seconds + td.days * 24 * 3600) * 10 ** 6) / 10 ** 6
 else:
     def bit_length(value):
         return value.bit_length()
 
+
     def total_seconds(td):
         return td.total_seconds()
 
-
 bit_length.__doc__ = 'Returns the bit length of an integer'
 total_seconds.__doc__ = 'Timedelta ``total_seconds`` with backported support in Python 2.6'
+
+
+class _EnumMetaClass(type):
+    """This is a deprecated, internal-only class in ion-python; do NOT use it for any reason.
+
+    Metaclass for simple enumerations.
+
+    Specifically provides the machinery necessary to emulate simplified Python 3.4 enumerations.
+    """
+
+    def __init__(cls, name, bases, attrs):
+        members = {}
+        # Re-bind any non magic-named method with an instance of the enumeration.
+        for attr_name, attr_value in iter(attrs.items()):
+            if not attr_name.startswith('_') and not callable(attr_value) and not isinstance(attr_value, property):
+                if not isinstance(attr_value, int):
+                    raise TypeError('Enum value must be an int: %r' % attr_value)
+                actual_value = cls(attr_name, attr_value)
+                setattr(cls, attr_name, actual_value)
+                members[attr_value] = actual_value
+
+        # Store the members reverse index.
+        cls._enum_members = members
+
+        type.__init__(cls, name, bases, attrs)
+
+    def __getitem__(cls, name):
+        """Looks up an enumeration value field by integer value."""
+        return cls._enum_members[name]
+
+    def __iter__(self):
+        """Iterates through the values of the enumeration in no specific order."""
+        return iter(self._enum_members.values())
+
+
+class Enum(int, metaclass=_EnumMetaClass):
+    """This is a deprecated, internal-only class in ion-python; do NOT use it for any reason
+
+    Simple integer based enumeration type.
+
+    Examples:
+        The typical declaration looks like::
+
+            class MyEnum(Enum):
+                A = 1
+                B = 2
+                C = 3
+
+        At this point ``MyEnum.A`` is an instance of ``MyEnum``.
+
+    Note:
+        Proper enumerations were added in Python 3.4 (PEP 435), this is a very simplified implementation
+        based loosely on that specification.
+
+        In particular, implicit order of the values is not supported.
+
+    Args:
+        value (int): the value associated with the enumeration.
+
+    Attributes:
+        name (str): The name of the enum.
+        value (int): The original value associated with the enum.
+    """
+    _enum_members = {}
+
+    def __new__(cls, name, value):
+        return int.__new__(cls, value)
+
+    def __init__(self, name, value):
+        warn(f'{self.__class__.__name__} is an internal-only class in ion-python; do not use it for any reason. This '
+             f'class is deprecated and may be removed without further warning in any future release. Use `IntEnum` '
+             f'instead.',
+             DeprecationWarning, stacklevel=2)
+        super().__init__()
+        self.name = name
+        self.value = value
+
+    def __init_subclass__(cls, **kwargs):
+        warn(f'{cls.__name__} is an internal-only class in ion-python; do not use it for any reason. This '
+             f'class is deprecated and may be removed without further warning in any future release. Use `IntEnum` '
+             f'instead.',
+             DeprecationWarning, stacklevel=2)
+        super().__init_subclass__(**kwargs)
+
+    def __getnewargs__(self):
+        return self.name, self.value
+
+    def __str__(self):
+        return '<%s.%s: %s>' % (type(self).__name__, self.name, self.value)
+
+    __repr__ = __str__
+
+
+

tests/test_util_enum.py

@@ -0,0 +1,54 @@
+# Copyright 2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License").
+# You may not use this file except in compliance with the License.
+# A copy of the License is located at:
+#
+#    http://aws.amazon.com/apache2.0/
+#
+# or in the "license" file accompanying this file. This file is
+# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS
+# OF ANY KIND, either express or implied. See the License for the
+# specific language governing permissions and limitations under the
+# License.
+
+import pytest
+
+from amazon.ion.util import Enum
+
+
+class SimpleEnum(Enum):
+    A = 1
+    B = 2
+
+
+def test_enum_members():
+    assert SimpleEnum._enum_members == {1: SimpleEnum.A, 2: SimpleEnum.B}
+
+
+def test_enum_reverse_lookup():
+    assert SimpleEnum[1] == SimpleEnum.A
+    assert SimpleEnum[2] == SimpleEnum.B
+
+
+def test_enum_fields():
+    assert SimpleEnum.A.value == 1
+    assert SimpleEnum.A.name == 'A'
+    assert SimpleEnum.B.value == 2
+    assert SimpleEnum.B.name == 'B'
+
+    values = list(SimpleEnum)
+    values.sort()
+    assert values == [SimpleEnum.A, SimpleEnum.B]
+
+
+def test_enum_as_int():
+    assert isinstance(SimpleEnum.A, int)
+    assert SimpleEnum.A == 1
+    assert SimpleEnum.A is not 1
+
+
+def test_malformed_enum():
+    with pytest.raises(TypeError):
+        class BadEnum(Enum):
+            A = 'Allo'