Exist: Templating and transform:transform: empty output on error

Created on 27 Jul 2018 · 9Comments · Source: eXist-db/exist

What is the problem

The templating system is used to provide the basic HTML for displaying the result of an XSL transformation:

<html data-template="wdb:getEE">
    <head><title>test</title></head>
    <body>
        <div id="wdbContent" data-template="wdb:getContent" />
    </body>
</html>

the function to apply the transformation is basically this:

declare function wdb:getContent($node as node(), $model as map(*)) {
  let $re :=
    try { transform:transform(doc($file), doc($xslt), $params, $attr, "expand-xincludes=no") }
    catch * { <h1>Error</h1> }

  return 
    <div id="wdbContent">
        {$re}
    </div>
};

this works fine if there are no errors in the XSLT. However, if there is an error, e.g. calling doc() on a file that does not exist, the output is an empty file:

<!DOCTYPE html>
<html></html>

What did you expect

The output of the given HTML in case of an error.

additional observations:

calling wdb:getContent with exactly the same parameters from eXide produces the expected output in case of an error
everything else inside the catch is processed correctly – I tried to console:log before returning output, which worked, and forwarding handling to another function: there, too, console:log worked but no output was produced
using transform:stream-transform returns the expected output in case of an error (but of course won't work correctly with the templating system)

Describe how to reproduce or add a test

The attached .zip contains an example. Store in /db/apps and call $server/exist/apps/catch/view.html.
If the line with doc() is commented out in the XSLT, you get “Testing”; if it is active, you get an empty response. If you use stream-transform instead of transform in app.xql, you get “error“ if the doc() line is active.
catch.zip

Context information

Please always add the following information

eXist-db: 4.3.0
Java version: 1.8.0_171
Operating system: tested on Ubuntu 16.04 and Windows 10
64 bit
How is eXist-db installed? JAR installer
Any custom changes in e.g. conf.xml: added an additional root to controller-config.xml on the Ubuntu machine; this is not present under Windows.

bug

Source

dariok

All 9 comments

How is $xslt constructed ?

dizzzz on 27 Jul 2018

I have installed your .zip file in 4.3.1 and see what I would expect when I call http://localhost:8080/exist/apps/catch/view.html and view source - the following HTML and not an "empty file," as you described it:

<!DOCTYPE html>
<html>
    <head>
        <title>test</title>
    </head>
    <body>
        <div id="wdbContent">
            <h1>error</h1>
        </div>
    </body>
</html>

joewiz on 27 Jul 2018

👍1

@joewiz: Indeed, app.xql in the zip contains "stream-transform()" from my testing (line 19). Change that to just "transform()" and you should observe the behaviour I described.

@dizzzz: from an XSLT file stored in the DB via doc(). See app.xql in my zip.

dariok on 28 Jul 2018

@dariok the reason I ask.... I typically read mail on a phone/tablet, opening attachments is somewhat cumbersome :-)

dizzzz on 28 Jul 2018

@dizzzz it is, indeed. I didn't mean to sound rude.

dariok on 28 Jul 2018

❤1

@dariok Thanks for the pointer. I've confirmed your results, and I've tried to reduce the files you've provided into a single, self-contained query that demonstrates the problem. Basically, I took modules/view.xql and brought all of the other aspects of the test into the file. Unfortunately, the query pegs my processor and runs out of memory for me with eXist 4.3.1. My hunch is that the core issue has to do with the way the templating module handles the call out to the transform functions. This is not good, but I'm not really sure how to attack the problem from here.

Does anyone have ideas for how best to proceed?

xquery version "3.1";

declare namespace config = "http://exist-db.org/xquery/apps/config";
declare namespace output = "http://www.w3.org/2010/xslt-xquery-serialization";
declare namespace wdb = "https://github.com/dariok/wdbplus/wdb";

declare option output:method "html5";
declare option output:media-type "text/html";

import module namespace console = "http://exist-db.org/xquery/console";
import module namespace templates = "http://exist-db.org/xquery/templates";

declare variable $doc := 
    <TEI xmlns="http://www.tei-c.org/ns/1.0" xml:id="test">
        <teiHeader/>
        <text>
            <body>
                <div>
                    <p>asdfa</p>
                </div>
            </body>
        </text>
    </TEI>;

declare variable $xslt := 
    <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" version="3.0">
        <xsl:template match="/">
            <h1>Testing</h1>
            <xsl:sequence select="doc('bogus')"/>
        </xsl:template>
    </xsl:stylesheet>;

declare function wdb:test($node as node(), $model as map(*), $transform-function as xs:string) {
    let $params :=
        <parameters>
            <param name="exist:stop-on-warn" value="no" />
            <param name="exist:stop-on-error" value="no" />
        </parameters>
    let $attrs := 
        <attributes>
            <attr name="http://saxon.sf.net/feature/recoveryPolicyName" value="recoverSilently" />
        </attributes>
    let $serialization-options := "expand-xincludes=no"
    let $transform-params := 
        [$doc, $xslt, $params, $attrs, $serialization-options]
(:        [$doc, $xslt]:)
    let $transform-arity := array:size($transform-params)
    let $transform := function-lookup(xs:QName("transform:" || $transform-function), $transform-arity)
    let $re :=
        try { 
            apply($transform, $transform-params) 
        }
        catch * { 
            let $t := console:log(
                <report>
                    {$params}
                    {$attrs}
                    <error>{$err:code || ': ' || $err:description}</error>
                    <error>{$err:module || '@' || $err:line-number ||':'||$err:column-number}</error>
                    <additional>{$err:additional}</additional>
                </report>
            )
            return
                <h1>error</h1>
        }
    return 
        <div id="wdbContent">
            {$re}
        </div>
};

let $lookup := 
    function($functionName as xs:string, $arity as xs:int) {
        try {
            function-lookup(xs:QName($functionName), $arity)
        } catch * {
            ()
        }
    }
let $config := map { $templates:CONFIG_STOP_ON_ERROR : true() }
for $transform-function in ("transform", "stream-transform")
let $content := 
    <html>
        <head>
            <title>test</title>
        </head>
        <body>
            <div id="wdbContent" data-template="wdb:getContent" data-template-transform-function="{$transform-function}"/>
        </body>
    </html>
return
    templates:apply($content, $lookup, (), $config)

joewiz on 30 Jul 2018

@joewiz do you think this could be another manifestation of this still open issue with templating: https://github.com/eXist-db/public-xar-repo/issues/21?