Re: [Xsltforms-support] conflict between subforms and the profiler?

[C. M. Sperberg-M. <cm...@bl...>]

On Jun 26, 2012, at 7:38 PM, C. M. Sperberg-McQueen wrote:

> I've encountered an unexpected behavior in 1.0RC.  I first encountered
> it in one of my own forms, but the simplest way to recreate it may be:
> 
> (1) Load the writers.xml example from the 1.0RC distribution, or from
> 
>    http://www.agencexml.com/xsltforms/writers.xml
> 
> (2) Click Show Books and Hide Books a few times.
> 
> (3) Click Profiler.
> 
> This ought in normal operation to produce a profile showing the profiler
> information we have all come to love.  What it produces instead, at the 
> moment, is a Javascript error message saying 
> 
>  XSLTForms Exception
>  --------------------------
> 
>  Error dispatching event 'xforms-model-construct' :
> 
>  xforms-link-exception


I think I have now identified the source of this error.

Adding calls to Xsltforms_browser.debugConsole.write
at various locations makes clear that the error is arising in the
Xsltforms_globals.profiling_data() function, specifically in the loop

	for (var expr in XsltForms_xpath.expressions) {
			if (XsltForms_xpath.expressions.hasOwnProperty(expr)) {
				exprtab[exprtab.length] = {expr: expr, evaltime: XsltForms_xpath.expressions[expr].evaltime};
			}
	}

When I load writers.xml and click the Profiler button before having 
unloaded any author's booklist, then this loop executes eight times,
for the expressions 

  . != 'true'
  @firstname
  @lastname
  @selected
  @selected != 'true'
  @selected = 'true'
  choose(@selected != 'true', 'Show', 'Hide')
  writer

These are the XPath expressions occurring in writers.xml.

When I load the subform, by clicking Show Books, and then click Profiler, 
the loop executes eleven times:  eight times for the XPath expressions shown
above, and three more times for

  @title
  @year
  book

These are the XPath expressions in books.xml, the subform.

When I then unload the subform by clicking Hide Books, and click Profiler
a third time, I get an error message in the Profiler window, and the debugging
trace in the main-form window shows the loop being entered nine times; it
looks a lot as if the error were being raised when the loop tries to evaluate
XsltForms_xpath.expressions['@title'].evaltime.  

A little further examination suggests that after the subform is
unloaded, XsltForms_xpath.expressions['@title'] is null, so 
the attempt to get its 'evaltime' property produces an error, 
which causes the load of the profiler to fail.  

Changing the conditional in lines 302-304 of xsltforms.js (in 1.0RC) to

  if (XsltForms_xpath.expressions.hasOwnProperty(expr) && XsltForms_xpath.expressions[expr]) {
     exprtab[exprtab.length] = {expr: expr, evaltime: XsltForms_xpath.expressions[expr].evaltime};
  }

seems to allow the Profiler to launch normally even after the subform is
unloaded.  

Michael

-- 
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* C. M. Sperberg-McQueen, Black Mesa Technologies LLC
* http://www.blackmesatech.com 
* http://cmsmcq.com/mib                 
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