Re: [xsl] Avoiding boneheaded mistakes in XSLT?

Subject: Re: [xsl] Avoiding boneheaded mistakes in XSLT?
From: Dimitre Novatchev <dnovatchev@xxxxxxxxx>
Date: Tue, 28 Dec 2010 16:18:43 -0800
> Do these sound familiar? Other favorite traps?

I think that one of the most common and difficult (at times with
almost unexplainable behavior) problem is the failure to provide
templates match certain nodes.

A good solution is to provide a "catch-all" template, for example:

<xsl:template match="*" priority="-20">
    ERROR: Unmatched element: <xsl:value-of select="name()"/>

This signals explicitly in any case when the node-list of an
<apply-templates> instruction contains an element that isn't matched
by a more specific template.

Dimitre Novatchev
Truly great madness cannot be achieved without significant intelligence.
To invent, you need a good imagination and a pile of junk
Never fight an inanimate object
You've achieved success in your field when you don't know whether what
you're doing is work or play
Facts do not cease to exist because they are ignored.

On Tue, Dec 28, 2010 at 2:35 PM, David Sewell <dsewell@xxxxxxxxxxxx> wrote:
> This is to some extent a general programming question, as it is possible
> with any programming language to write something that is syntactically
> legitimate (i.e., does not throw a compile- or run-time error) but fails
> to produce expected results because of a mistake in logic or something
> else. I'm sure we've all had the experience of beating our heads against
> a programming failure that turns out to be the result of a very simple
> (aka "boneheaded") mistake that seems obvious when found. It seems to me
> that this is perhaps more likely with XSLT/XPath than some other
> environments, because of (1) the general verbosity of expression, and
> (2) the many complexities of return values when you're working with a
> combination of XML documents and fragments, and sequences of nodes
> and/or atomic values.
> Over the last few days I've been working on some especially complex
> transforms and have lost more time that I'd like owing to some of these
> simple mistakes. Not the first time by a long shot I've made them, either.
> example:
> 1. In an XPath expression, using "something/node" where I wanted
> "something/node()" [ditto text vs. text()]: always means zero results and
> can drive you crazy if you don't notice the missing parentheses;
> 2. Using xsl:copy-of instead of xsl:apply-templates in a case where
> recursive processing is in fact needed on the item in question;
> 3. Using xsl:value-of when you really need xsl:copy-of for a variable
> that is a sequence;
> 4. Bad logic with xsl:analyze-string, putting processing into
> xsl:non-matching-substring that should have gone into
> xsl:matching-substring or vice versa.
> Do these sound familiar? Other favorite traps?
> Has anyone come up with a useful list of "things to check any time my
> code is not working the way it should"?
> DS
> --
> David Sewell, Editorial and Technical Manager
> ROTUNDA, The University of Virginia Press
> PO Box 400314, Charlottesville, VA 22904-4314 USA
> Email: dsewell@xxxxxxxxxxxx B  Tel: +1 434 924 9973
> Web:

Current Thread