xsl:assert
Used to make assertions in the form of XPath expressions, causing a dynamic error if the assertion turns out to be false.
Category: instruction
Content:
sequence-constructor
Permitted parent elements:
any XSLT element whose content model is sequence
constructor; any literal result element
Attributes
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XPath expression to be asserted. |
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Details
It may be useful to add an attribute such as use-when="$DEBUG" to
xsl:assert instructions; the global static variable
DEBUG can then be used to switch assertion processing on and
off. The variable might be declared as <xsl:variable name="DEBUG"
as="xs:boolean" select="true()"/>.
Examples
The following code tests whether the value of $x is
non-negative, and if not, fails with an error message: