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f865d0feab
What annoyed me for a long time was the fact, that in order to break
into a new paragraph, you need to insert </para><para> in the
description attribute of an option.
Now we will automatically create <para/> elements for every block that
is separated by two consecutive newlines.
I first tried to do this within options-to-docbook.xsl, but it turns
out[1] that this isn't directly possible with XSLT 1.0, so I added
another XSLT file that postprocesses the option descriptions that are
now enclosed in <nixos:option-description/> by options-to-docbook.xsl.
The splitting itself is a bit more involved, because we can't simply
split on every \n\n because we'd also split text nodes of elements, for
example:
<screen><![CDATA[
one line
another one
]]></screen>
This would create one <para/> element for "one line" and another for
"another line", which we obviously don't want because <screen/> is used
to display verbatim contents of what a user is seeing on the screen.
So what we do instead is splitting *only* the top-level text nodes
within the outermost <para/> and leave all elements as-is. If there are
more than one <para/> elements at the top-level, we simply don't process
it at all, because the description then already contains </para><para>.
https://www.mhonarc.org/archive/html/xsl-list/2012-09/msg00319.html
Signed-off-by: aszlig <aszlig@nix.build>
Cc: @edolstra, @domenkozar
115 lines
4.8 KiB
XML
115 lines
4.8 KiB
XML
<?xml version="1.0"?>
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<xsl:stylesheet version="1.0"
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xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
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xmlns:str="http://exslt.org/strings"
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xmlns:exsl="http://exslt.org/common"
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xmlns:db="http://docbook.org/ns/docbook"
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xmlns:nixos="tag:nixos.org"
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extension-element-prefixes="str exsl">
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<xsl:output method='xml' encoding="UTF-8" />
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<xsl:template match="@*|node()">
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<xsl:copy>
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<xsl:apply-templates select="@*|node()" />
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</xsl:copy>
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</xsl:template>
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<xsl:template name="break-up-description">
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<xsl:param name="input" />
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<xsl:param name="buffer" />
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<!-- Every time we have two newlines following each other, we want to
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break it into </para><para>. -->
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<xsl:variable name="parbreak" select="'

'" />
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<!-- Similar to "(head:tail) = input" in Haskell. -->
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<xsl:variable name="head" select="$input[1]" />
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<xsl:variable name="tail" select="$input[position() > 1]" />
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<xsl:choose>
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<xsl:when test="$head/self::text() and contains($head, $parbreak)">
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<!-- If the haystack provided to str:split() directly starts or
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ends with $parbreak, it doesn't generate a <token/> for that,
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so we are doing this here. -->
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<xsl:variable name="splitted-raw">
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<xsl:if test="starts-with($head, $parbreak)"><token /></xsl:if>
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<xsl:for-each select="str:split($head, $parbreak)">
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<token><xsl:value-of select="node()" /></token>
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</xsl:for-each>
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<!-- Something like ends-with($head, $parbreak), but there is
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no ends-with() in XSLT, so we need to use substring(). -->
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<xsl:if test="
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substring($head, string-length($head) -
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string-length($parbreak) + 1) = $parbreak
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"><token /></xsl:if>
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</xsl:variable>
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<xsl:variable name="splitted"
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select="exsl:node-set($splitted-raw)/token" />
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<!-- The buffer we had so far didn't contain any text nodes that
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contain a $parbreak, so we can put the buffer along with the
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first token of $splitted into a para element. -->
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<para xmlns="http://docbook.org/ns/docbook">
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<xsl:apply-templates select="exsl:node-set($buffer)" />
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<xsl:apply-templates select="$splitted[1]/node()" />
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</para>
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<!-- We have already emitted the first splitted result, so the
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last result is going to be set as the new $buffer later
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because its contents may not be directly followed up by a
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$parbreak. -->
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<xsl:for-each select="$splitted[position() > 1
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and position() < last()]">
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<para xmlns="http://docbook.org/ns/docbook">
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<xsl:apply-templates select="node()" />
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</para>
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</xsl:for-each>
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<xsl:call-template name="break-up-description">
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<xsl:with-param name="input" select="$tail" />
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<xsl:with-param name="buffer" select="$splitted[last()]/node()" />
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</xsl:call-template>
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</xsl:when>
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<!-- Either non-text node or one without $parbreak, which we just
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want to buffer and continue recursing. -->
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<xsl:when test="$input">
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<xsl:call-template name="break-up-description">
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<xsl:with-param name="input" select="$tail" />
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<!-- This essentially appends $head to $buffer. -->
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<xsl:with-param name="buffer">
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<xsl:if test="$buffer">
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<xsl:for-each select="exsl:node-set($buffer)">
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<xsl:apply-templates select="." />
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</xsl:for-each>
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</xsl:if>
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<xsl:apply-templates select="$head" />
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</xsl:with-param>
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</xsl:call-template>
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</xsl:when>
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<!-- No more $input, just put the remaining $buffer in a para. -->
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<xsl:otherwise>
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<para xmlns="http://docbook.org/ns/docbook">
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<xsl:apply-templates select="exsl:node-set($buffer)" />
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</para>
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</xsl:otherwise>
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</xsl:choose>
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</xsl:template>
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<xsl:template match="nixos:option-description">
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<xsl:choose>
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<!--
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Only process nodes that are comprised of a single <para/> element,
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because if that's not the case the description already contains
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</para><para> in between and we need no further processing.
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-->
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<xsl:when test="count(db:para) > 1">
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<xsl:apply-templates select="node()" />
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</xsl:when>
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<xsl:otherwise>
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<xsl:call-template name="break-up-description">
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<xsl:with-param name="input"
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select="exsl:node-set(db:para/node())" />
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</xsl:call-template>
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</xsl:otherwise>
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</xsl:choose>
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</xsl:template>
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</xsl:stylesheet>
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