Node positional calculation not working dynamically

[pbowen-oc]

The attached form attempts to read in from the clinicaldata instance using three different methods:

1. Using node position: [1]
2. Using node position: [position()=${rownum}] where ${rownum} = 1 (from a calculate item = position(..))
3. Using node position: [number(${rownum})] where ${rownum} = 1 (from a calculate item = position(..))

Only the first method reads in the value successfully. The other options read in null. All three were expected to work.

Method #2 was in use on the original source form prior to deploying 2.5.6.oc-5 and working successfully then. Since that time, it reads no data.

XForm: NodePositionCalc.xml.txt

Clinicaldata instance: NodePositionCalc.clinicaldata.xml.txt

[MartijnR]

http://localhost:8005/?xform=NodePositionCalc.xml

• create a minimal test form

[MartijnR]

I believe the two none-working formulas are evaluating correctly because current() is missing in the predicate (same as #398 (comment)). That would be a pyxform issue then. Will confirm.

• run original form in enketo-express-oc with correction of predicate to current()/../rownum to confirm that the XForm is wrong - confirmed
• test similar xlsform in latest pyxform - did not do after discovering open bug report
• file bug report in pyxform if necessary

[MartijnR]

Pyxform issue already posted: XLSForm/pyxform#490 (and it looks like I was aware that OpenClinica needed this fix)

[MartijnR]

Method #2 was in use on the original source form prior to deploying 2.5.6.oc-5 and working successfully then. Since that time, it reads no data.

Definitely no recent change in this very elementary XPath evaluation in Enketo. XPath expressions are clearly incorrect. However, in the past pyxform would have generated an absolute path for ${rownum}, which though this was also incorrect, may have caused this to be evaluated as desired.

To bypass the pyxform bug, remove the ${node} references and replace by beautiful pure XPath

current	replace with
[position()=${rownum}]	[position()=current()/../rownum]
number(${rownum})	number(current()/../rownum)

[pbowen-oc]

@MartijnR - Thanks. Am I correct in assuming that we will need to take this approach for now for any item references used in the instance expression? Is this syntax going to vary if the item being referenced is in a different group than the item that has this instance expression?

[pbowen-oc]

I have created a new Pyxform issue (XLSForm/pyxform#531) since the previous fix was incomplete and did not handle expressions that contained spaces.

[pbowen-oc]

This is all set.