Fix errors when instantiating custom classes

Defining a custom object/observable/extension class with no custom
__init__() function would result in an `AttributeError` or `TypeError`,
depending on if the class sub-classed `object` or not.

stix2/__init__.py

@@ -9,8 +9,8 @@ from .common import (TLP_AMBER, TLP_GREEN, TLP_RED, TLP_WHITE, CustomMarking,
 from .core import Bundle, _register_type, parse
 from .environment import Environment, ObjectFactory
 from .observables import (URL, AlternateDataStream, ArchiveExt, Artifact,
-                          AutonomousSystem, CustomObservable, Directory,
-                          DomainName, EmailAddress, EmailMessage,
+                          AutonomousSystem, CustomExtension, CustomObservable,
+                          Directory, DomainName, EmailAddress, EmailMessage,
                           EmailMIMEComponent, File, HTTPRequestExt, ICMPExt,
                           IPv4Address, IPv6Address, MACAddress, Mutex,
                           NetworkTraffic, NTFSExt, PDFExt, Process,

stix2/observables.py

@@ -836,7 +836,14 @@ def CustomObservable(type='x-custom-observable', properties=None):
 
             def __init__(self, **kwargs):
                 _Observable.__init__(self, **kwargs)
-                cls.__init__(self, **kwargs)
+                try:
+                    cls.__init__(self, **kwargs)
+                except (AttributeError, TypeError) as e:
+                    # Don't accidentally catch errors raised in a custom __init__()
+                    if ("has no attribute '__init__'" in str(e) or
+                            str(e) == "object.__init__() takes no parameters"):
+                        return
+                    raise e
 
         _register_observable(_Custom)
         return _Custom
@@ -883,7 +890,14 @@ def CustomExtension(observable=None, type='x-custom-observable', properties={}):
 
             def __init__(self, **kwargs):
                 _Extension.__init__(self, **kwargs)
-                cls.__init__(self, **kwargs)
+                try:
+                    cls.__init__(self, **kwargs)
+                except (AttributeError, TypeError) as e:
+                    # Don't accidentally catch errors raised in a custom __init__()
+                    if ("has no attribute '__init__'" in str(e) or
+                            str(e) == "object.__init__() takes no parameters"):
+                        return
+                    raise e
 
         _register_extension(observable, _Custom)
         return _Custom

stix2/sdo.py

@@ -346,7 +346,14 @@ def CustomObject(type='x-custom-type', properties=None):
 
             def __init__(self, **kwargs):
                 _STIXBase.__init__(self, **kwargs)
-                cls.__init__(self, **kwargs)
+                try:
+                    cls.__init__(self, **kwargs)
+                except (AttributeError, TypeError) as e:
+                    # Don't accidentally catch errors raised in a custom __init__()
+                    if ("has no attribute '__init__'" in str(e) or
+                            str(e) == "object.__init__() takes no parameters"):
+                        return
+                    raise e
 
         stix2._register_type(_Custom)
         return _Custom

stix2/test/test_custom.py

@@ -104,6 +104,26 @@ def test_custom_object_type():
     assert "'property2' is too small." in str(excinfo.value)
 
 
+def test_custom_object_no_init():
+    @stix2.sdo.CustomObject('x-new-obj', [
+        ('property1', stix2.properties.StringProperty(required=True)),
+    ])
+    class NewObj():
+        pass
+
+    no = NewObj(property1='something')
+    assert no.property1 == 'something'
+
+    @stix2.sdo.CustomObject('x-new-obj2', [
+        ('property1', stix2.properties.StringProperty(required=True)),
+    ])
+    class NewObj2(object):
+        pass
+
+    no2 = NewObj2(property1='something')
+    assert no2.property1 == 'something'
+
+
 def test_parse_custom_object_type():
     nt_string = """{
         "type": "x-new-type",
@@ -153,6 +173,26 @@ def test_custom_observable_object():
     assert "'property2' is too small." in str(excinfo.value)
 
 
+def test_custom_observable_object_no_init():
+    @stix2.observables.CustomObservable('x-new-observable', [
+        ('property1', stix2.properties.StringProperty()),
+    ])
+    class NewObs():
+        pass
+
+    no = NewObs(property1='something')
+    assert no.property1 == 'something'
+
+    @stix2.observables.CustomObservable('x-new-obs2', [
+        ('property1', stix2.properties.StringProperty()),
+    ])
+    class NewObs2(object):
+        pass
+
+    no2 = NewObs2(property1='something')
+    assert no2.property1 == 'something'
+
+
 def test_custom_observable_object_invalid_ref_property():
     with pytest.raises(ValueError) as excinfo:
         @stix2.observables.CustomObservable('x-new-obs', [
@@ -364,6 +404,26 @@ def test_custom_extension_invalid_observable():
     assert "Custom observables must be created with the @CustomObservable decorator." in str(excinfo.value)
 
 
+def test_custom_extension_no_init():
+    @stix2.observables.CustomExtension(stix2.DomainName, 'x-new-extension', {
+        'property1': stix2.properties.StringProperty(required=True),
+    })
+    class NewExt():
+        pass
+
+    ne = NewExt(property1="foobar")
+    assert ne.property1 == "foobar"
+
+    @stix2.observables.CustomExtension(stix2.DomainName, 'x-new-ext2', {
+        'property1': stix2.properties.StringProperty(required=True),
+    })
+    class NewExt2(object):
+        pass
+
+    ne2 = NewExt2(property1="foobar")
+    assert ne2.property1 == "foobar"
+
+
 def test_parse_observable_with_custom_extension():
     input_str = """{
         "type": "domain-name",