Remove non-matching parent elements in XSL

Question

• I need to remove all Component elements and their corresponding ComponentRef elements, where the Component child element File attribute Source is NOT a dll file?
• I have the evaluation function for the Source string value i.e. {substring(wix:File/@Source, string-length(wix:File/@Source) - 2)}='dll' returns true for Source values that contain dll
• But I don't know how to use the function to remove the last two Component elements (with their children) as well as the corresponding last two ComponentRef elements (mapped by Id attribute)?

Source XML

<?xml version="1.0" encoding="utf-8"?>
<Wix xmlns="http://schemas.microsoft.com/wix/2006/wi">
    <Fragment>
        <DirectoryRef Id="TARGETFOLDER">
            <Component Id="cmpA733DB49D89AC9CEA2EDFAAEE51992E7" Guid="{F3412A8F-5718-45AB-9E6F-7B802BCC0EED}">
                <File Source="$(var.WixSlave.TargetDir)\protobuf-net.dll" Id="fil910D6DB28382BAB5A9DF0ACBD5095ADE" KeyPath="yes" />
            </Component>
            <Component Id="cmpF1D751B9621E283AD7BDAA8BC6997338" Guid="{20C09DBB-C8D6-43CF-A9D6-C823850F86F6}">
                <File Source="$(var.WixSlave.TargetDir)\client.wyc" Id="fil7454A527FA7C3918A537EB96235C9F5F" KeyPath="yes"  />
            </Component>
            <Component Id="cmp8CDA926DD93F7CEFBF8FFF444D5828F4" Guid="{2243D9D8-C172-4FFE-AEBE-43659294E55D}">
                <File Source="$(var.WixSlave.TargetDir)\protobuf-net.pdb" Id="fil3EA19C07C51C4E31D37065B3A8620713" KeyPath="yes"  />
            </Component>
        </DirectoryRef>
    </Fragment>
    <Fragment>
        <ComponentGroup Id="Dlls">
            <ComponentRef Id="cmpA733DB49D89AC9CEA2EDFAAEE51992E7" />
            <ComponentRef Id="cmpF1D751B9621E283AD7BDAA8BC6997338" />
            <ComponentRef Id="cmp8CDA926DD93F7CEFBF8FFF444D5828F4" />
        </ComponentGroup>
    </Fragment>
</Wix>

Dysfunctional XSLT Stub

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" xmlns="http://schemas.microsoft.com/wix/2006/wi" xmlns:wix="http://schemas.microsoft.com/wix/2006/wi" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:template match="node()|@*">
        <xsl:copy>
            <xsl:apply-templates select="node()|@*"/>
        </xsl:copy>
    </xsl:template>
    <xsl:template match="wix:File[{substring(wix:File/@Source, string-length(wix:File/@Source) - 2)}!='dll']"/>
</xsl:stylesheet>

• This XSLT does not work in many ways, firstly the second match complains, and I'm not sure what is wrong with the expression..

• Even if that worked, how would you always retain DirectoryRef while removing the mismatching Component and child File elements?

• Removing the corresponding ComponentRef elements is missing altogether?

Desired XML Output

<?xml version="1.0" encoding="utf-8"?>
<Wix xmlns="http://schemas.microsoft.com/wix/2006/wi">
    <Fragment>
        <DirectoryRef Id="TARGETFOLDER">
            <Component Id="cmpA733DB49D89AC9CEA2EDFAAEE51992E7" Guid="{F3412A8F-5718-45AB-9E6F-7B802BCC0EED}">
                <File Source="$(var.WixSlave.TargetDir)\protobuf-net.dll" Id="fil910D6DB28382BAB5A9DF0ACBD5095ADE" KeyPath="yes" />
            </Component>
        </DirectoryRef>
    </Fragment>
    <Fragment>
        <ComponentGroup Id="Dlls">
            <ComponentRef Id="cmpA733DB49D89AC9CEA2EDFAAEE51992E7" />
        </ComponentGroup>
    </Fragment>
</Wix>

Answer 1

Here's how I would go about it:

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" xmlns="http://schemas.microsoft.com/wix/2006/wi" xmlns:wix="http://schemas.microsoft.com/wix/2006/wi" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

    <xsl:key name="component-id" match="//wix:Component[substring(wix:File/@Source, string-length(wix:File/@Source) - 2) != 'dll']" use="@Id"/>

    <xsl:template match="node()|@*">
        <xsl:copy>
            <xsl:apply-templates select="node()|@*"/>
        </xsl:copy>
    </xsl:template>

    <xsl:template match="wix:Component[@Id = key('component-id', @Id)/@Id]"/>

    <xsl:template match="wix:ComponentRef[@Id = key('component-id', @Id)/@Id]"/>
</xsl:stylesheet>

The idea is rather simple. Tell XSLT processor to build an index of those Component nodes we want removed and then suppress the xsl:copy with a matching template.