Re: [xsl] Need an XPath expression which returns all xs:pattern elements containing a regex that permits an unbounded number of characters

["David Carlisle d.p.carlisle@xxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

On Thu, 4 Apr 2024 at 15:38, Piez, Wendell A. (Fed) wendell.piez@xxxxxxxx <
xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:

> Holla again,
>
>
>
> With every reason to trust David C, nonetheless wouldnbt it be fine if we
> could, say, set up a bunch of unit tests to actually determine which of
> these subtle incantations do as we think they do?
>
>
>
> An XSpec sheet could be wired to test both regex-based and parsing-based
> solutions as implemented in XSLT, to give Roger the confidence he needs in
> his approach.
>
>
>
> I jump in to mention of XSpec mainly because these questions are
> surrounded by the problem of whatbs beasyb. It depends. Maybe
paper-napkin
> analysis followed by some interactive free-form testing is good enough.
>
>
>
> Cheers, Wendell
>


Oh now I'm hurt that you suggest Roger may fear a typo in my famously
accurate typing:(

Actually I suspect the real question is not "is this well tested" it's "why
are you asking this question"?

I suspect it's really not the right question to be asking.

For example if * and + are being banned to disallow some long strings as
part or preventing some DOS attack then
a finite string match such as x{0,100000000000000000000000}  is likely to
be just as problematic.
so a well tested accurate test for really infinite matches may not really
help




>
>
> *From:* David Carlisle d.p.carlisle@xxxxxxxxx <
> xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>
> *Sent:* Thursday, April 4, 2024 10:21 AM
> *To:* xsl-list@xxxxxxxxxxxxxxxxxxxxxx
> *Subject:* Re: [xsl] Need an XPath expression which returns all
> xs:pattern elements containing a regex that permits an unbounded number of
> characters
>
>
>
>
>
>
>
> On Thu, 4 Apr 2024 at 14:48, Willem Van Lishout willemvanlishout@xxxxxxxxx
> <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Is this even possible, theoretically speaking? As soon as you start using
> lookaheads, square brackets, and so on, your patterns will likely fail. I
> don't think regex can parse regex.
>
>
>
>
>
>
>
> I don't think the regex needs to be parsed here: you can destructively
> normalise it before testing eg
>
> replace ( replace(replace(,.'\s','') , '\\.' , 'x'), `\{-0-9]*,\}`,'*`)
>
>
>
> would get rid of all white space, replace  \-quoted characters by x and
> a{ 99, } constructs by a*
>
> which should simplify looking for * and +
>
>
>
> David
>
>
>
> 4 Apr 2024, at 20:15, "David Carlisle d.p.carlisle@xxxxxxxxx" <
> xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>
>
>
>
>
> On Thu, 4 Apr 2024 at 13:29, Roger L Costello costello@xxxxxxxxx <
> xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hi Folks,
>
> I want to find, in an XML Schema, all xs:pattern elements containing a
> regex that permits an unbounded number of characters.
>
> Here are examples of xs:pattern elements that I want to find:
>
> <xs:pattern value="A*"/>
> <xs:pattern value="A+"/>
> <xs:pattern value="A{0,.}"/>
> <xs:pattern value="A{1,.}"/>
>
>
> How to fix my XPath expression? Is the solution to add a second predicate:
>
> xs:pattern[
>         contains(@value, '*') or
>         contains(@value, '+') or
>         contains(@value, '{1,}') or
>         contains(@value, '{0,}')
>     ][
>         not(contains(@value, '\*')) and
>         not(contains(@value, '\+'))
>     ]
>
> Is that correct?
>
>
>
> No.
>
>
>
> A  pattern \\*   matches an unbounded list of backslashes  but fails your
> test as it contains \*
>
> A pattern X{5,}  matches an unbounded list  of X of at least 5 but doesn't
> match your first predicate.
>
>
>
>
>
>
>
>
>
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