Python extension: SNMP Get returns empty string when the index (IID) does not exist. Expected: None

[alinstroe]

Running net-snmp/python/netsnmp/tests

Step 1. Run unmodified BasicTests.test_v1_get (perform SNMP Get on sysDescr.0)
BasicTests.test_v1_get

---v1 GET tests -------------------------------------

v1 snmpget result: ('My Router',)

v1 get var: sysDescr 0 = My Router ( OCTETSTR )

---

Ran 1 test in 0.217s

OK

Step 2. Modify the test to perform SNMP Get on sysDescr.123 (non-existent IID)

---v1 GET tests -------------------------------------

v1 snmpget result: ('',) #empty string

v1 get var: sysDescr 123 = ( OCTETSTR )

At step 2 the expected result is an error or None obj. Instead I receive an empty string for an OID that doesn't exist.
This behavior is not dependent on the SNMP version (it's the same for v1, v2c, v3)

The same result (empty string) can also be obtained when we perform SNMP GET on an OID which is supposed to return an empty string.
So, we can't decide if it's an error or valid result.

Thanks.

[bvanassche]

Please reopen this bug report if the commit mentioned above would not be sufficient.

[alinstroe]

---v1 GET tests -------------------------------------

v1 snmpget result: ('My Router',)

v1 get var: sysDescr 0 = My Router ( OCTETSTR )
.

---v1 GET test of nonexistent OID -------------------

v1 snmpget result: (None,)

v1 get var: .1.3.6.1.2.1.1.1.123 0 = None ( None )

---

Ran 3 tests in 0.270s

OK

Seems to be working.
Thanks.