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

["Dimitre Novatchev dnovatchev@xxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

Hi Roger,

In order to deal with '\' used as an escape character, then such a solution
must ignore '\\' as this is not an escape character but represents the
(regular) character `\`.
In the same way, '\\\\' represents 2 (regular) consecutive '\' characters,
..., and so on, ...
And a sequence of odd-number of backslashes should be replaced by a single
backslash character.

A subexpression doing this must precede any further processing.

One such subexpression is:

    replace($input, '(\\\\)+', '')

Then on the result of the above (using the above result as the input) one
can check for a single '\' followed by any wanted strings.



Thanks,
Dimitre

On Thu, Apr 4, 2024 at 5:29b/AM 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,.}"/>
>
> I do not want either of the following xs:pattern elements because -- due
> to the escape symbol -- they do not permit an unbounded number of
> characters:
>
> <xs:pattern value="A\*"/>
> <xs:pattern value="A\+"/>
>
> I created an XPath 2.0 expression to find the desired xs:pattern elements:
>
> xs:pattern[
>         contains(@value, '*') or
>         contains(@value, '+') or
>         contains(@value, '{1,}') or
>         contains(@value, '{0,}')
>     ]
>
> Eek! That is not correct. It incorrectly returns the xs:pattern elements
> with escaped asterisk and escaped plus symbols:
>
> <xs:pattern value="A\*"/>
> <xs:pattern value="A\+"/>
>
> 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? Is that the best approach? Is there a better approach?
>
> Bonus points if you can answer this question: Is my XPath expression
> catching all xs:pattern elements that have a regex that permits an
> unbounded number of characters?
>
> Note: For reasons that I will not explain, the XPath expression must be an
> XPath 2.0 expression.
>
> /Roger