XPATH Positions in Policy subtlety

[geoffc]

I have noticed this before, and know how to fix it, but I was wondering what I am doing wrong here.

So in XPATH, $VAR is a nodeset with some values.

$VAR[2] should select the second node.

If $I=2, then $VAR[$I] should do the same thing.

But often I find that $VAR[$I] does not work, but that $VAR[position())=$I] does work.

Semantically [$I] and [position()=$I] should be the same... Yet they are often not...

I thought, maybe, $I is not coming across as a number, and maybe the test for position()= is a string compare?  But that seems odd.

I tested, by setting $I as XPATAH of number(1).  Then when I increment it in XPATH as number($I) + number(1) and same issue.

Then I tried in my $VAR[$I] doing it as $VAR[number($I)]

But $VAR[position()=$I] continues to work.  Anyone have an idea?

[lhaeger]

I would guess your variable is a string in those cases where it does not work as expected, not a number. DirXMLScript has only three variable types: string, nodeset and object, no number type. So you'd have to make sure it's of object type with a number assigned in the moment you use it as a position descriptor. If you use a comparison like position()=$var then whatever $var is will be converted to a number using the number() function internally and you'll see the result you expected even if $var is string of digits.

Test :      Action: do-set-local-variable("nodeset",scope="policy",arg-node-set(token-src-attr("Internet EMail Address"))).
Test :        arg-node-set(token-src-attr("Internet EMail Address"))
Test :          token-src-attr("Internet EMail Address")
Test :            Query from policy
Test :            
<nds dtdversion="4.0" ndsversion="8.x">
  <source>
    <product version="4.8.2.0">DirXML</product>
    <contact>NetIQ Corporation</contact>
  </source>
  <input>
    <query class-name="User" dest-dn="o=dirXML Test\ou=Users\cn=User1" scope="entry">
      <read-attr attr-name="Internet EMail Address"/>
    </query>
  </input>
</nds>
Test :            Query from policy result
Test :            
<nds dtdversion="4.0" ndsversion="8.x">
  <source>
    <product version="4.8.2.0">DirXML</product>
    <contact>NetIQ Corporation</contact>
  </source>
  <output>
    <instance class-name="User">
      <attr attr-name="Internet EMail Address">
        <value type="string">geoffc@cisny.com</value>
        <value type="string">geoffrey@gmail.org</value>
      </attr>
    </instance>
  </output>
</nds>
Test :          Token Value: {<value> @type = "string",<value> @type = "string"}.
Test :          Arg Value: {<value> @type = "string",<value> @type = "string"}.
Test :      Action: do-set-local-variable("spos",scope="policy","2").
Test :        arg-string("2")
Test :          token-text("2")
Test :          Arg Value: "2".
Test :      Action: do-set-local-variable("npos",scope="policy",arg-object(token-xpath("number("2")"))).
Test :        arg-object(token-xpath("number("2")"))
Test :          token-xpath("number("2")")
Test :      Action: do-set-local-variable("mail",scope="policy",token-xpath("$nodeset[$spos]")).
Test :        arg-string(token-xpath("$nodeset[$spos]"))
Test :          token-xpath("$nodeset[$spos]")
Test :            Token Value: "geoffc@cisny.com".
Test :          Arg Value: "geoffc@cisny.com".
Test :      Action: do-set-local-variable("mail",scope="policy",token-xpath("$nodeset[position()=$spos]")).
Test :        arg-string(token-xpath("$nodeset[position()=$spos]"))
Test :          token-xpath("$nodeset[position()=$spos]")
Test :            Token Value: "geoffrey@gmail.org".
Test :          Arg Value: "geoffrey@gmail.org".
Test :      Action: do-set-local-variable("mail",scope="policy",token-xpath("$nodeset[$npos]")).
Test :        arg-string(token-xpath("$nodeset[$npos]"))
Test :          token-xpath("$nodeset[$npos]")
Test :            Token Value: "geoffrey@gmail.org".
Test :          Arg Value: "geoffrey@gmail.org".
Test :      Action: do-set-local-variable("mail",scope="policy",token-xpath("$nodeset[position()=$npos]")).
Test :        arg-string(token-xpath("$nodeset[position()=$npos]"))
Test :          token-xpath("$nodeset[position()=$npos]")
Test :            Token Value: "geoffrey@gmail.org".
Test :          Arg Value: "geoffrey@gmail.org".

 Comparisons in xpath have a few unintuitive touches, from https://www.w3.org/TR/1999/REC-xpath-19991116/#booleans:

When neither object to be compared is a node-set and the operator is = or !=, then the objects are compared by converting them to a common type as follows and then comparing them.

If at least one object to be compared is a boolean, then each object to be compared is converted to a boolean as if by applying the boolean function.

Otherwise, if at least one object to be compared is a number, then each object to be compared is converted to a number as if by applying the number function.

Otherwise, both objects to be compared are converted to strings as if by applying the string function.

[geoffc]

I agree with your point.  But I have tried using number() on the value in multiple places trying to ensure that the string variable is distinctly a number. 

Still not working the way I want. Now this could be a Simulator issue since I happen to be working in it offline this morning. I wonder if maybe it is a Simulator'ism? 

But glad I am not missing anything very obvious.