WIP: forward referenced ASN.1 types

7 files changed, 84 insertions, 4 deletions

diff --git a/CHANGES.rst b/CHANGES.rst
index 85870ae..2109016 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -1,4 +1,10 @@
 
+Revision 0.4.1, released XX-08-2017
+-----------------------------------
+
+- Forward-referencing ASN.1 types implemented to handle
+  the case of recursive ASN.1 schemas.
+
 Revision 0.3.4, released XX-08-2017
 -----------------------------------
 
diff --git a/pyasn1/__init__.py b/pyasn1/__init__.py
index 8b713b4..42f4704 100644
--- a/pyasn1/__init__.py
+++ b/pyasn1/__init__.py
@@ -1,7 +1,7 @@
 import sys
 
 # http://www.python.org/dev/peps/pep-0396/
-__version__ = '0.3.4'
+__version__ = '0.4.1'
 
 if sys.version_info[:2] < (2, 4):
     raise RuntimeError('PyASN1 requires Python 2.4 or later')
diff --git a/pyasn1/type/base.py b/pyasn1/type/base.py
index 822f947..07f716e 100644
--- a/pyasn1/type/base.py
+++ b/pyasn1/type/base.py
@@ -428,7 +428,7 @@ class AbstractConstructedMeta(type):
     def __init__(cls, name, bases, nmspc):
         super(AbstractConstructedMeta, cls).__init__(name, bases, nmspc)
 
-        forwardref.ForwardRef.newTypeNotification(name, cls)
+        forwardref.ForwardRef.newTypeNotification(name, cls())
 
 
 class AbstractConstructedAsn1Item(Asn1ItemBase, metaclass=AbstractConstructedMeta):
diff --git a/pyasn1/type/forwardref.py b/pyasn1/type/forwardref.py
new file mode 100644
index 0000000..c822419
--- /dev/null
+++ b/pyasn1/type/forwardref.py
@@ -0,0 +1,45 @@
+#
+# This file is part of pyasn1 software.
+#
+# Copyright (c) 2005-2017, Ilya Etingof <etingof@gmail.com>
+# License: http://pyasn1.sf.net/license.html
+#
+from pyasn1 import error
+
+
+__all__ = ['ForwardRef']
+
+
+class ForwardRef(object):
+    # TODO: this is not thread-safe
+    waitingList = {}
+
+    def __init__(self, symbol, *args, **kwargs):
+        self.__symbol = symbol
+        self.args = args
+        self.kwargs = kwargs
+
+    def callLater(self, cbFun):
+        if self.__symbol not in self.waitingList:
+            self.__class__.waitingList[self.__symbol] = []
+        self.waitingList[self.__symbol].append((self, cbFun))
+
+    # TODO: make two callbacks - one for updating types and the other for
+    # initialization once all updates are done
+    @classmethod
+    def newTypeNotification(cls, name, obj):
+        # TODO: name collision at different modules possible
+        if name in cls.waitingList:
+            for waitingObject, cbFun in cls.waitingList.pop(name):
+
+                cbFun(obj.clone(*waitingObject.args, **waitingObject.kwargs))
+
+    def subtype(self, *args, **kwargs):
+        # TODO: make a copy; combine kw/args to mimic subtype/clone ops
+        self.args = args
+        self.kwargs = kwargs
+        return self
+
+    def __getattr__(self, item):
+        raise error.PyAsn1Error('Unresolved forward reference %s (.%s attempted)' % (self.__symbol, item))
+
diff --git a/pyasn1/type/namedtype.py b/pyasn1/type/namedtype.py
index 0d56f77..c484dfd 100644
--- a/pyasn1/type/namedtype.py
+++ b/pyasn1/type/namedtype.py
@@ -110,6 +110,7 @@ class NamedTypes(object):
     def __init__(self, *namedTypes, **kwargs):
         self.__namedTypes = namedTypes
         self.__namedTypesLen = len(self.__namedTypes)
+        self.__nameToPosMap = self.__computeNameToPosMap()
 
         def updateNameType(self, idx, name, obj):
             # TODO: better way to do in-place update?
@@ -130,7 +131,6 @@ class NamedTypes(object):
             return
         # TODO: verify initialization status
         self.__minTagSet = self.__computeMinTagSet()
-        self.__nameToPosMap = self.__computeNameToPosMap()
         self.__tagToPosMap = self.__computeTagToPosMap()
         self.__ambiguousTypes = 'terminal' not in kwargs and self.__computeAmbiguousTypes() or {}
         self.__uniqueTagMap = self.__computeTagMaps(unique=True)
diff --git a/pyasn1/type/univ.py b/pyasn1/type/univ.py
index b83c3ec..131c35b 100644
--- a/pyasn1/type/univ.py
+++ b/pyasn1/type/univ.py
@@ -1723,6 +1723,17 @@ class SequenceOfAndSetOfBase(base.AbstractConstructedAsn1Item):
 
         base.AbstractConstructedAsn1Item.__init__(self, **kwargs)
 
+        def updateComponentType(self, obj):
+            self._componentType = obj
+
+        import functools
+        from pyasn1.type import forwardref
+
+        if isinstance(self.componentType, forwardref.ForwardRef):
+            cbFun = functools.partial(updateComponentType, self)
+            self.componentType.callLater(cbFun)
+
+
     # Python list protocol
 
     def clear(self):
diff --git a/tests/type/test_univ.py b/tests/type/test_univ.py
index b9fcce4..b6ff31e 100644
--- a/tests/type/test_univ.py
+++ b/tests/type/test_univ.py
@@ -1120,7 +1120,25 @@ class Sequence(unittest.TestCase):
         assert not s[1][1].isValue
 
         # TODO: SequenceOf, Choice, en/decoding
-        # TODO: dynamic type def use-case
+
+    def testSelfReferencingDynamicDef(self):
+
+        s = univ.Sequence(
+            componentType=namedtype.NamedTypes(
+                namedtype.NamedType('name', univ.Integer()),
+                namedtype.OptionalNamedType('selfref', forwardref.ForwardRef('sft'))
+            )
+        )
+
+        s.componentType['selfref'].asn1Object.newTypeNotification('sft', s)
+
+        s[0] = 0
+        s[1][0] = 1
+
+        assert s[0] == 0
+        assert s[1][0] == 1
+        assert not s[1][1].isValue
+
 
 class SetOf(unittest.TestCase):
     def setUp(self):