Re: [pyasn1-users] "Duplicate positive key" while decoding

[David J. <dav...@fr...>]

Ilya, great thanks. I've managed to get it working. Kudos for making 
such a great lib!

As a side note (maybe a bug hides in this), should the call to method 
setComponentByName below a reference to q or a reference to a newly 
created instance of Query.Constraint?

q = Query()
c = q.setComponentByName("constraint")
assert(q is c) # currently this line raises no error

On 20. 09. 2016 12:13, Ilya Etingof wrote:
>
> That is quite fair: Constraint is a pure SEQUENCE while
> Query["constraint"] is a tagged subtype of Constraint. Formally, these
> are different types so they are not interchangeable.
>
> One solution would be to subtype the Constraint and/or Expression:
>
>   Constraint ::= [0] SEQUENCE {
>        field ENUMERATED { source, target, date },
>        operator ENUMERATED { eq, neq, gt, gte, lt, lte },
>        value Value
>   }
>
>   Query ::= CHOICE { constraint Constraint, expression Expression }
>
> Or, in Python code, instantiate from Query["constraint"]:
>
>   q = Query()
>   # this call will instantiate new Query.Constraint object
>   c = q.setComponentByName("constraint")
>   c["field"] = "source"
>   c["operator"] = "eq"
>   c["value"] = Value()
>   c["value"]["entity"] = "David"
>
> To nitpick: AUTOMATIC TAGS might not be used as you are tagging things
> manually.
>
> On 09/20/2016 11:03 AM, David Jelenc wrote:
>> Many thanks for your response, Greg.
>>
>> I've updated my schema to reflect your suggestions, but now I have
>> troubles constructing messages. The updated schema is the following:
>>
>> MySchema DEFINITIONS AUTOMATIC TAGS ::= BEGIN
>>
>> Query ::= CHOICE { constraint [0] Constraint, expression [1] Expression }
>>
>> Constraint ::= SEQUENCE {
>>     field ENUMERATED { source, target, date },
>>     operator ENUMERATED { eq, neq, gt, gte, lt, lte },
>>     value Value
>> }
>>
>> Value ::= CHOICE { entity [0] PrintableString, date [1] INTEGER }
>>
>> Expression ::= SEQUENCE {
>>     operator ENUMERATED { and, or, not },
>>     operands SEQUENCE OF Query
>> }
>>
>> END
>>
>> I've generated Python classes with asn1ate and I omit them here for
>> brevity's sake. Now, If I try to construct a message ...
>>
>> c = Constraint()
>> c["field"] = "source"
>> c["operator"] = "eq"
>> c["value"] = Value()
>> c["value"]["entity"] = "David"
>>
>> q = Query()
>> q["constraint"] = c #
>>
>> .. I get an error in the the last line. The error is the following:
>>
>> Component value is tag-incompatible:
>> Constraint(componentType=NamedTypes(NamedType('field', Enumerated(,
>> NamedValues(('source', 0), ('target', 1), ('date', 2)))),
>> NamedType('operator', Enumerated(, NamedValues(('eq', 0), ('neq', 1),
>> ('gt', 2), ('gte', 3), ('lt', 4), ('lte', 5)))), NamedType('value',
>> Value(componentType=NamedTypes(NamedType('entity',
>> PrintableString(tagSet=TagSet((), Tag(tagClass=128, tagFormat=0,
>> tagId=0)))), NamedType('date', Integer(tagSet=TagSet((),
>> Tag(tagClass=128, tagFormat=0,
>> tagId=1))))))))).setComponents(Enumerated('source',
>> NamedValues(('source', 0), ('target', 1), ('date', 2))),
>> Enumerated('eq', NamedValues(('eq', 0), ('neq', 1), ('gt', 2), ('gte',
>> 3), ('lt', 4), ('lte', 5))),
>> Value(componentType=NamedTypes(NamedType('entity',
>> PrintableString(tagSet=TagSet((), Tag(tagClass=128, tagFormat=0,
>> tagId=0)))), NamedType('date', Integer(tagSet=TagSet((),
>> Tag(tagClass=128, tagFormat=0,
>> tagId=1)))))).setComponents(PrintableString('David', tagSet=TagSet((),
>> Tag(tagClass=128, tagFormat=0, tagId=0))))) vs
>> Constraint(componentType=NamedTypes(NamedType('field', Enumerated(,
>> NamedValues(('source', 0), ('target', 1), ('date', 2)))),
>> NamedType('operator', Enumerated(, NamedValues(('eq', 0), ('neq', 1),
>> ('gt', 2), ('gte', 3), ('lt', 4), ('lte', 5)))), NamedType('value',
>> Value(componentType=NamedTypes(NamedType('entity',
>> PrintableString(tagSet=TagSet((), Tag(tagClass=128, tagFormat=0,
>> tagId=0)))), NamedType('date', Integer(tagSet=TagSet((),
>> Tag(tagClass=128, tagFormat=0, tagId=1)))))))), tagSet=TagSet((),
>> Tag(tagClass=128, tagFormat=32, tagId=0)))
>>
>> To my lay understanding, the error suggest that the constraint is an
>> invalid type to be set in the constraint field of a Query message. I'm
>> not sure how to proceed with this.
>>
>> As always, I thank anyone willing to share their thoughts.
>>
>> Best,
>> David
>>
>>
>> On 19. 09. 2016 17:29, Greg Hudson wrote:
>>> On 09/19/2016 11:07 AM, David Jelenc wrote:
>>>> Query ::= CHOICE { constraint Constraint, expression Expression }
>>>> Constraint ::= SEQUENCE { [...]
>>>> Expression ::= SEQUENCE { [...]
>>>
>>> An ASN.1 CHOICE must have different tags for each option (X.680 section
>>> 28.7).  Both of the options for this type have the same tag (for
>>> SEQUENCE), so the decoder can't tell which option was chosen.  If you
>>> have control over the schema, try:
>>>
>>>     Query ::= CHOICE { constraint [0] Constraint, expression [1]
>>> Expression }
>>>
>>> This will add a context tag to each option, ensuring that they use
>>> different tags.  (If encoded size is a serious consideration, you can
>>> get away with adding a context tag to only one of the options.)
>>>
>>
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