Re: [xsl] Avoiding boneheaded mistakes in XSLT?

[Wendell Piez <wapiez@xxxxxxxxxxxxxxxx>]

Hi again,

On 12/30/2010 8:48 AM, Michael Kay wrote:
> Producing warnings for constructs that could be correct comes into a
> different category. Saxon has always produced some such warnings for
> things that are obviously wrong, even though legal (for example @A/@B),
> and I think there is plenty more scope to be smarter. For example, If
> someone writes book/isbn when the schema (or indeed the instance)
> contains book/@isbn, I think the probability that this is incorrect is
> sufficiently high to justify a warning, provided it can be suppressed at
> user option.

Personally I'm very sympathetic to Dimitre's caution about all this. 
Saxon now warns when, for example, one tries to select "text()" from an 
attribute context. Fair enough. But this sometimes leads to unwanted 
messages when one has done this on purpose. For example, maybe you have 
written a Schematron that matches on attributes, and the built-in 
Schematron implementation (which happens to be Saxon running an XSLT) 
ends up throwing this error. And the framework in which you are running 
Schematron doesn't give you access to the switches for the instance of 
Saxon that runs it....

I certainly concur that the warning message should be turned off by 
default. But remember not everyone running XSLT has the means to tweak 
these settings. Of course, as far as Saxon is concerned, Mike gets to 
make the judgement call. But personally I'm of the mind that this 
particular kind of error is one you learn to watch out for, and if you 
know enough to control all the switches and settings for your tools, you 
probably also know enough to diagnose and fix it without the tool's help.

The contrapositive of this is "if you don't know enough to diagnose and 
fix this problem without a tool's help, you probably also don't know how 
to control the switches and settings for your tools."

Cheers,
Wendell

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Wendell Piez                            mailto:wapiez@xxxxxxxxxxxxxxxx
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