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Re: try/catch with messages

From: Imsieke, Gerrit, le-tex <gerrit.imsieke@le-tex.de>
Date: Thu, 17 Apr 2014 07:56:06 +0200
Message-ID: <534F6CF6.2020501@le-tex.de>
To: xproc-dev@w3.org
Hi Graham,

There's a port called 'error' in the p:catch branch [1]. You need to 
forward this port to some other port that you declare both for the 
p:group and for the p:catch branch. In the example below, I added a 
'status' port to the pipeline where there will either be an <ok/> 
document or the forwarded error port of p:catch. It's a bit verbose, 
admittedly, but that's how XProc is sometimes.

Gerrit

[1] http://www.w3.org/TR/xproc/#p.catch


<p:declare-step
   xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
   xmlns:xs="http://www.w3.org/2001/XMLSchema"
   xmlns:p="http://www.w3.org/ns/xproc"
   version="1.0">		
   <p:input port="source" primary="true">			
     <p:inline>
       <doc>Hello World!</doc>
     </p:inline>
   </p:input>
   <p:output port="result" primary="true"/>
   <p:output port="status">
     <p:pipe port="status" step="try-test"/>
   </p:output>
   <p:option name="terminate" required="false" select="'yes'"/>

   <p:try name="try-test">
     <p:group>
       <p:output port="status">
         <p:inline>
           <ok/>
         </p:inline>
       </p:output>
       <p:output port="result" primary="true"/>
       <p:xslt name="tester">
         <p:with-param name="terminate" select="$terminate" />
         <p:input port="stylesheet">
           <p:inline>
             <xsl:stylesheet version="2.0">
               <xsl:param name="terminate" as="xs:string"/>
               <xsl:template match="/">
                 <xsl:message terminate="{$terminate}">in XSLT step 
named 'tester'</xsl:message>
                 <xsl:copy-of select="."/>
               </xsl:template>
             </xsl:stylesheet>
           </p:inline>		
         </p:input>
         <p:input port="parameters">
           <p:empty/>
         </p:input>
       </p:xslt>
     </p:group>
     <p:catch name="catch">
       <p:output port="status">
         <p:pipe port="result" step="forward-errors"/>
       </p:output>
       <p:output port="result" primary="true">
         <p:inline>
           <nodoc/>
         </p:inline>
       </p:output>
       <p:identity name="forward-errors">
         <p:input port="source">
           <p:pipe port="error" step="catch"/>
         </p:input>
       </p:identity>
       <p:sink/>
     </p:catch>
   </p:try>

</p:declare-step>

On 16.04.2014 17:27, Graham Seaman wrote:
> Thanks Jonathan,
>
> That's a really helpful resource, and has cleared up a lot of my
> questions about the operation of ports. Unfortunately the try/catch
> examples generate an inline output in the catch sections, rather than
> trying to access the error which made the try fail, as I'm trying to do.
>
> The following example now at least runs (using the same xml/xslt as
> before). However, while a successful 'try' correctly outputs the xslt
> transform output, when it fails because the xslt has terminated with an
> xsl:message, the catch section simply reproduces the original input. I
> still can't work out how to connect the catch input to the xslt error
> message, instead of to the initial input.
>
> <?xml version="1.0" encoding="UTF-8"?>
>
> <p:declare-step xmlns:p="http://www.w3.org/ns/xproc" version="1.0">		
> 	<p:input port="source" primary="true">			
> 		<p:document href="test.xml"/>
> 	</p:input>
> 	<p:output port="result" primary="true" sequence="false"/>
> 	
> 	<p:try name="try-test">
> 		<p:group>
> 			<p:xslt name="tester">
> 				<p:input port="stylesheet">
> 					<p:document href="test.xslt"/>		
> 				</p:input>
> 				<p:input port="parameters" sequence="true">
> 					<p:empty/>
> 				</p:input>
> 			</p:xslt>
> 		</p:group>
> 		<p:catch>
> 			<p:filter select="/"/>
> 		</p:catch>
> 	</p:try>
>
> </p:declare-step>
>
> Graham
>
> On 15/04/14 21:58, Cranford, Jonathan W. wrote:
>> Graham,
>>
>> There's an example of try..catch embedded in the XProc tutorial at http://xfront.com/xproc/index.html, by Roger Costello and James Garriss.
>>
>> Look specifically at xproc/labs/lab09_try_catch in the zip file.
>>
>> This is a really good resource that was invaluable to me when first learning XProc.
>>
>> HTH,
>>
>> Jonathan Cranford
>>
>>
>>> -----Original Message-----
>>> From: Graham Seaman [mailto:graham@theseamans.net]
>>> Sent: Tuesday, April 15, 2014 4:48 AM
>>> To: xproc-dev@w3.org
>>> Subject: try/catch with messages
>>>
>>> Hi,
>>>
>>> I'm in the 'initial 5 minutes' stage of learning xproc, and floundering.
>>> I have a series of xslt templates intended to validate files in
>>> different ways. If validation fails at any point, the xslt terminates
>>> with an error message (ie. using xsl;message with terminate='yes'). I'm
>>> hoping to persuade xproc to catch and display the message produced in
>>> the xslt, and would ideally like the xproc pipeline also to terminate at
>>> that point. However, I haven't even been able to get try/catch working
>>> yet. Below is a (clearly non-working) attempt with some toy xml/xslt. I
>>> think in general the biggest problem I'm having is with the scope of the
>>> various ports (for example, I don't understand why the global pipeline
>>> source port is not visible to the p:xslt stage without adding a 'dummy'
>>> parameter).
>>>
>>> Thanks for any advice
>>>
>>> Graham
>>>
>>>
>>>
>>> <?xml version="1.0" encoding="UTF-8"?>
>>>
>>> <p:declare-step xmlns:p="http://www.w3.org/ns/xproc" version="1.0">
>>>     <p:input port="source" primary="true" sequence="false">
>>>         <p:document href="test.xml"/>
>>>     </p:input>
>>>     <p:output port="result" primary="true" sequence="false"/>
>>>
>>>     <p:try name="try-test">
>>>         <p:group>
>>>             <p:xslt name="tester">
>>>                 <p:input port="stylesheet">
>>>                     <p:document href="test.xslt"/>
>>>                 </p:input>
>>>                 <p:with-param name="dummy" select="''"/>
>>>             </p:xslt>
>>>         </p:group>
>>>         <p:catch>
>>>             <p:identity>
>>>                 <p:input port="source">
>>>                     <p:pipe step="tester" port="error"/>
>>>                 </p:input>
>>>             </p:identity>
>>>         </p:catch>
>>>     </p:try>
>>>
>>>     <p:identity>
>>>         <p:input port="source">
>>>             <p:pipe step="try-test" port="result"/>
>>>         </p:input>
>>>     </p:identity>
>>>
>>> </p:declare-step>
>>>
>>> -------------------
>>>
>>> <?xml version="1.0" encoding="UTF-8"?>
>>>
>>> <words>
>>>     <phrase>Hallo world</phrase>
>>>     <phrase>and it's goodbye from me</phrase>
>>> </words>
>>>
>>> -----------------------
>>>
>>> <?xml version="1.0" encoding="UTF-8"?>
>>> <xsl:stylesheet version="2.0"
>>>     xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
>>>
>>>     <xsl:template match="@* | node()">
>>>         <xsl:copy>
>>>             <xsl:apply-templates select="@*, node()"/>
>>>         </xsl:copy>
>>>     </xsl:template>
>>>
>>>     <xsl:template match="phrase">
>>>         <xsl:if test="text() = 'and it''s goodbye from me'">
>>>             <xsl:message terminate="yes">test.xml matched
>>> phrase</xsl:message>
>>>         </xsl:if>
>>>         <xsl:copy-of select="."/>
>>>     </xsl:template>
>>> </xsl:stylesheet>
>>>
>>>
>>>
>>
>>
>
>

-- 
Gerrit Imsieke
Geschäftsführer / Managing Director
le-tex publishing services GmbH
Weissenfelser Str. 84, 04229 Leipzig, Germany
Phone +49 341 355356 110, Fax +49 341 355356 510
gerrit.imsieke@le-tex.de, http://www.le-tex.de

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Received on Thursday, 17 April 2014 05:56:46 UTC

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