为什么不能将 xsl:value-of 放入 fo:block 中？

Question

I have the following XSL file:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="2.0"
                xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                xmlns:fo="http://www.w3.org/1999/XSL/Format">
    <xsl:output media-type="text" omit-xml-declaration="yes"/>

    <xsl:template match="root/branch">

        <fo:root>

            <fo:layout-master-set>
                <fo:simple-page-master master-name="simple"
                                       page-height="29.7cm"
                                       page-width="21cm"
                                       margin-top="1cm"
                                       margin-bottom="2cm"
                                       margin-left="2.5cm"
                                       margin-right="2.5cm">
                    <fo:region-body margin-top="3cm"/>
                    <fo:region-before extent="3cm"/>
                    <fo:region-after extent="1.5cm"/>
                </fo:simple-page-master>
            </fo:layout-master-set>

            <fo:page-sequence master-reference="simple">
                <fo:flow flow-name="xsl-region-body">

                    <fo:block font-size="12pt"
                              font-family="sans-serif"
                              line-height="15pt"
                              space-after.optimum="3pt"
                              text-align="justify">
                        <xsl:value-of select="branch/greenLeave"/>
                        <xsl:value-of select="branch/yellowLeave"/>
                    </fo:block>

                </fo:flow>
            </fo:page-sequence>
        </fo:root>
    </xsl:template>
</xsl:stylesheet>

When I open it in IDEA IntelliJ, I get the following error message:

Does anybody know what is wrong here? I cannot find a plausible explanation.

Answer 1

Seems like the XSD for FOP which I downloaded from https://svn.apache.org/repos/asf/xmlgraphics/fop/trunk/fop/src/foschema/fop.xsd lacked support for nested XSL-T statements.

As a workaround, I manually added a

<any processContent="skip"/>

to that XSD file at the right place.