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Re: [xsl] Keeping result-document() from writing to a file more than once?

2019-04-18 17:16:47
The rules are designed, in principle, to ensure that there is no dependency on 
order of execution, and in particular, that a URI that is written to during a 
transformation can never be read during the same transformation, either before 
or after the writing (because there is no mutable state, therefore no "before" 
and "after", in a functional world). If you use doc-available() on a particular 
URI, and xsl:result-document on the same URI, then either doc-available() 
should return false, or xsl:result-document should fail. 

This doesn't seem to be what you are observing, which could indicate 
non-conformant behaviour.

But basically, what you are doing shouldn't work. It should not be possible to 
detect any change in the state of persistent filestore during the course of a 
transformation by calling doc-available(), or otherwise (except by use of 
extension functions, which don't have to follow any rules).

Solving your problem (preventing result-document from writing to a file more 
than once) has to be done in a different way: it's essentially the same as any 
other de-duplication or grouping task. You have to find all the references to a 
given URI and process them as a group. You can't do it (unless you cheat) by 
peeking into filestore to see if it has changed.

Michael Kay
Saxonica

On 18 Apr 2019, at 22:56, dvint(_at_)dvint(_dot_)com 
<xsl-list-service(_at_)lists(_dot_)mulberrytech(_dot_)com> wrote:

I'm processing some DITA xml files with XSLT. I'm reading these files and 
where they have a conref into some other content (think xinclude) that is 
included in the current file. There may be multiple things shared out from 
one large file (topic). I want to make a new file for each of the shared 
pieces.
 
 More than one file can reference exactly the same content, so after 
processing all these files I want a single file representing the shared 
content. It is this multiple references to the same content that causes the 
duplication of the file that the result-document() function doesn't like. 
this is the code that I have for detecting this situation:
 
 <xsl:variable name="newFile" select="concat($srcFile, '-', $target, 
'-output.dita')" />
 
 
 
 NEW FILE <xsl:value-of select="$newFile"/> 
 
 Doc available: <xsl:value-of select="doc-available($newFile)"/> 
 
 
 <xsl:if test="not(doc-available($newFile))" 
 
 CREATE FILE NOW 
 
 <xsl:result-document method="xml" href="{$newFile}" indent="yes">
 <referable-content id="ikj1555615661716" xml:lang="en-us">
 <titler>efereable test</title>
 <rcbody>
 <xsl:copy-of select="document($srcFile)//*[@id = $target]"/>
 </rcbody>
 </referable-content>
 </xsl:result-document>
 
 </xsl:if>
 
 
 
 
 
 Here are a series of messages created as i process the files. Notice that 
the first message correctly identifies the file 
"conref-para_content.dita-simpletable_nohead-output.dita" as not existing and 
produces output. If you then look at the last one you will see the same file 
being referenced and tries to write to the file again. But in other places 
you see the test working properly and not creating a new file:
 
 
 
 
 
 file 'conref-para_content.dita' 
 NEW FILE 
/Users/danvint/pubsrc-other/formatting-sample/conref-para_content.dita-simpletable_nohead-output.dita
 Doc available: false'
 
 CREATE FILE NOW
 
 file 'conref-para_content.dita' 
 NEW FILE 
/Users/danvint/pubsrc-other/formatting-sample/conref-para_content.dita-simpletable_head-output.dita
 Doc available: true'
 
 file 'conref-para_content.dita' 
 NEW FILE 
/Users/danvint/pubsrc-other/formatting-sample/conref-para_content.dita-table_head-output.dita
 Doc available: true'
 
 file 'conref-para_content.dita' 
 NEW FILE 
/Users/danvint/pubsrc-other/formatting-sample/conref-para_content.dita-table_nohead-output.dita
 Doc available: true'
 
 file 'conref-para_content.dita' 
 NEW FILE 
/Users/danvint/pubsrc-other/formatting-sample/conref-para_content.dita-simpletable_nohead-output.dita
 Doc available: false'
 
 CREATE FILE NOW
 
 
 
I believe the doc-available() reads the file to be XML. So when the script 
stops there is a file in the OS but it is empty due to the second write 
failing. Running this in oXygen I get the results of what should have been 
written showing up in a window. I cut and pasted that content into the empty 
file and reran it. Processing got further along and stopped on a second file 
with the same message. I did the same thing, with the new content in this 
second file and it now runs to completion if all the files exist.

If I delete all the files that were generated, I'm back to the same problem. 
Is there some delay in writing the output that I should  be accounting for? 
Is there a sleep() function in XSLT or something to cause a delay or flush 
the buffer?
 
 Any ideas on what I can check?
 
 
 
 ..dan
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