Boost C++ Libraries: Ticket #5210: JSON writer does not allow attributes and children in the same node

status changed; resolution set

Sebastian Redl — Wed, 23 Feb 2011 16:17:39 GMT

status new → closed
resolution → invalid

A property tree node can have both data and children, i.e. a tree can look like this:

root:                           <- has only children
  child1: "child 1 data"        <- has both data and children
    child1.1: "child 1.1 data"  <- has only data
    child1.2: "child 1.2 data"  <- has only data
  child2: "child 2 data"        <- has only data

There is no way to represent such a tree as JSON. A JSON node can be an object (it has named children), an array (it has unnamed children), or a basic data item (string, number, boolean, null). There is no JSON node that can have both direct data and children.

Therefore, the validation function rejects such trees when generating JSON.

attachment set

anonymous — Wed, 18 May 2011 15:31:51 GMT

attachment → test_property_tree.cpp

attachment set

anonymous — Wed, 18 May 2011 15:32:03 GMT

attachment → Shop.xml

status changed; resolution deleted

Wed, 18 May 2011 15:34:07 GMT

status closed → reopened
resolution invalid

Thanks. I see this check is mandatory. I was poking into this function only for the sole reason that the error indicated it while i was playing a simple XML to JSON conversion. For instance:

<object>
        <type>Shop</type>
        <POC>
                <name>Private Investigation</name>
                <street>221B Baker Street</street>
                <town>London</town>
                <zip>NW1 6XE</zip>
                <country>United Kingdom</country>
        </POC>
        <workingDays>
            <Monday/>
            <Saturday/>
            <Sunday/>
        </workingDays>
</object>

This simple XML file is read in without any trouble. But if i walk through the resulting ptree and print all key and value contents, then it looks like this:

object: "
"
    type: "Private Investigation"
    POC: "
        "
        name: "Cabbies United"
        street: "221B Baker Street"
        town: "London"
        zip: "NW1 6XE"
        country: "United Kingdom"
    workingDays: "
        "
        Monday: ""
        Saturday: ""
        Sunday: ""

The attempt to serialize in JSON this ptree fails, because of the empty strings stored in the value fields of the keys object, POC, and workingDays. As the original XML has no attributes for these tags i am quite puzzled where these are coming from.

See the attached files for the small test i wrote. This fails for version 1.46.0 and 1.46.1.

status changed; resolution set

Sebastian Redl — Wed, 18 May 2011 18:05:03 GMT

status reopened → closed
resolution → invalid

Your XML contains whitespace between the various elements, and it is preserved. Therefore, the nodes contain both data and children, which, as mentioned, is not allowed for the JSON writer.

Pass trim_whitespace to read_xml, and it should collapse and remove the whitespace.