From be7de7d7a72ed73777bcae6eff0ba0f698172548 Mon Sep 17 00:00:00 2001
From: Ilya Etingof <etingof@gmail.com>
Date: Sun, 23 Jun 2019 09:04:26 +0200
Subject: Fix `var-bindings` initialization

Set `var-bindings` to an empty sequence by default. Otherwise
it can remain a "pyasn1 schema object" failing to encode. This
can happen with newer pyasn1 versions where `SequenceOf` type
does not have default initializer.
---
 CHANGES.txt             | 3 +++
 pysnmp/proto/api/v1.py  | 7 +++++--
 pysnmp/proto/api/v2c.py | 3 ++-
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/CHANGES.txt b/CHANGES.txt
index 3c9a1ddd..8ed4fe9b 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -107,6 +107,9 @@ Revision 4.4.10, released 2019-04-XX
 - Fixed asyncore main loop to respect non-default timer resolution
 - Fixed `.setTimerResolution()` behaviour of abstract main loop dispatcher
   to update call intervals of the existing periodic dispatcher jobs
+- Fixed `var-bindings` initialization to prevent pyasn1 encoder failures
+  with newer pyasn1 versions where `SequenceOf` type looses its default
+  initializer.
 
 Revision 4.4.9, released 2019-02-09
 -----------------------------------
diff --git a/pysnmp/proto/api/v1.py b/pysnmp/proto/api/v1.py
index f13920e7..e8641deb 100644
--- a/pysnmp/proto/api/v1.py
+++ b/pysnmp/proto/api/v1.py
@@ -80,7 +80,9 @@ class PDUAPI(object):
             2, self._errorIndex, verifyConstraints=False, matchTags=False,
             matchConstraints=False)
 
-        pdu.setComponentByPosition(3)
+        varBindList = pdu.setComponentByPosition(3).getComponentByPosition(3)
+        varBindList.clear()
+
 
     @staticmethod
     def getRequestID(pdu):
@@ -217,7 +219,8 @@ class TrapPDUAPI(object):
             4, self._zeroTime, verifyConstraints=False, matchTags=False,
             matchConstraints=False)
 
-        pdu.setComponentByPosition(5)
+        varBindList = pdu.setComponentByPosition(5).getComponentByPosition(5)
+        varBindList.clear()
 
     @staticmethod
     def getEnterprise(pdu):
diff --git a/pysnmp/proto/api/v2c.py b/pysnmp/proto/api/v2c.py
index c415ca9a..0470fafd 100644
--- a/pysnmp/proto/api/v2c.py
+++ b/pysnmp/proto/api/v2c.py
@@ -119,7 +119,8 @@ class BulkPDUAPI(PDUAPI):
             2, self._maxRepetitions, verifyConstraints=False, matchTags=False,
             matchConstraints=False)
 
-        pdu.setComponentByPosition(3)
+        varBindList = pdu.setComponentByPosition(3).getComponentByPosition(3)
+        varBindList.clear()
 
     @staticmethod
     def getNonRepeaters(pdu):
-- 
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