forked from lix-project/lix
primops: Move toXML to primops/toXML.cc
Change-Id: I8da29345903015e38b9832f0d9b4011dc5bbb17b
This commit is contained in:
parent
a93af3f92f
commit
c96f5bcdd2
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@ -103,6 +103,7 @@ libexpr_sources = files(
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'primops/path.cc',
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'primops/path.cc',
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'primops/string.cc',
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'primops/string.cc',
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'primops/system.cc',
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'primops/system.cc',
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'primops/toXML.cc',
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'primops/types.cc',
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'primops/types.cc',
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'value/context.cc',
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'value/context.cc',
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)
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)
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@ -186,110 +186,6 @@ static void derivationStrictInternal(EvalState & state, const std::string & name
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/* Convert the argument (which can be any Nix expression) to an XML
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/* Convert the argument (which can be any Nix expression) to an XML
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representation returned in a string. Not all Nix expressions can
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representation returned in a string. Not all Nix expressions can
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be sensibly or completely represented (e.g., functions). */
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be sensibly or completely represented (e.g., functions). */
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static void prim_toXML(EvalState & state, const PosIdx pos, Value * * args, Value & v)
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{
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std::ostringstream out;
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NixStringContext context;
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printValueAsXML(state, true, false, *args[0], out, context, pos);
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v.mkString(out.str(), context);
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}
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static RegisterPrimOp primop_toXML({
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.name = "__toXML",
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.args = {"e"},
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.doc = R"(
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Return a string containing an XML representation of *e*. The main
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application for `toXML` is to communicate information with the
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builder in a more structured format than plain environment
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variables.
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Here is an example where this is the case:
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```nix
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{ stdenv, fetchurl, libxslt, jira, uberwiki }:
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stdenv.mkDerivation (rec {
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name = "web-server";
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buildInputs = [ libxslt ];
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builder = builtins.toFile "builder.sh" "
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source $stdenv/setup
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mkdir $out
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echo "$servlets" | xsltproc ${stylesheet} - > $out/server-conf.xml ①
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";
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stylesheet = builtins.toFile "stylesheet.xsl" ②
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"<?xml version='1.0' encoding='UTF-8'?>
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<xsl:stylesheet xmlns:xsl='http://www.w3.org/1999/XSL/Transform' version='1.0'>
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<xsl:template match='/'>
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<Configure>
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<xsl:for-each select='/expr/list/attrs'>
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<Call name='addWebApplication'>
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<Arg><xsl:value-of select=\"attr[@name = 'path']/string/@value\" /></Arg>
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<Arg><xsl:value-of select=\"attr[@name = 'war']/path/@value\" /></Arg>
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</Call>
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</xsl:for-each>
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</Configure>
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</xsl:template>
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</xsl:stylesheet>
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";
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servlets = builtins.toXML [ ③
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{ path = "/bugtracker"; war = jira + "/lib/atlassian-jira.war"; }
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{ path = "/wiki"; war = uberwiki + "/uberwiki.war"; }
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];
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})
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```
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The builder is supposed to generate the configuration file for a
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[Jetty servlet container](http://jetty.mortbay.org/). A servlet
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container contains a number of servlets (`*.war` files) each
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exported under a specific URI prefix. So the servlet configuration
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is a list of sets containing the `path` and `war` of the servlet
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(①). This kind of information is difficult to communicate with the
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normal method of passing information through an environment
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variable, which just concatenates everything together into a
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string (which might just work in this case, but wouldn’t work if
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fields are optional or contain lists themselves). Instead the Nix
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expression is converted to an XML representation with `toXML`,
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which is unambiguous and can easily be processed with the
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appropriate tools. For instance, in the example an XSLT stylesheet
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(at point ②) is applied to it (at point ①) to generate the XML
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configuration file for the Jetty server. The XML representation
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produced at point ③ by `toXML` is as follows:
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```xml
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<?xml version='1.0' encoding='utf-8'?>
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<expr>
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<list>
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<attrs>
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<attr name="path">
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<string value="/bugtracker" />
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</attr>
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<attr name="war">
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<path value="/nix/store/d1jh9pasa7k2...-jira/lib/atlassian-jira.war" />
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</attr>
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</attrs>
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<attrs>
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<attr name="path">
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<string value="/wiki" />
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</attr>
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<attr name="war">
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<path value="/nix/store/y6423b1yi4sx...-uberwiki/uberwiki.war" />
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</attr>
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</attrs>
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</list>
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</expr>
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```
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Note that we used the `toFile` built-in to write the builder and
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the stylesheet “inline” in the Nix expression. The path of the
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stylesheet is spliced into the builder using the syntax `xsltproc
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${stylesheet}`.
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)",
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.fun = prim_toXML,
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});
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/* Store a string in the Nix store as a source file that can be used
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/* Store a string in the Nix store as a source file that can be used
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115
src/libexpr/primops/toXML.cc
Normal file
115
src/libexpr/primops/toXML.cc
Normal file
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@ -0,0 +1,115 @@
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#include "primops.hh"
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#include "value-to-xml.hh"
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namespace nix {
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/**
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* builtins.toXML
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*/
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static void prim_toXML(EvalState & state, const PosIdx pos, Value ** args, Value & v)
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{
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std::ostringstream out;
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NixStringContext context;
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printValueAsXML(state, true, false, *args[0], out, context, pos);
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v.mkString(out.str(), context);
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}
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static RegisterPrimOp primop_toXML({
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.name = "__toXML",
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.args = {"e"},
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.doc = R"(
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Return a string containing an XML representation of *e*. The main
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application for `toXML` is to communicate information with the
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builder in a more structured format than plain environment
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variables.
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Here is an example where this is the case:
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```nix
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{ stdenv, fetchurl, libxslt, jira, uberwiki }:
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stdenv.mkDerivation (rec {
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name = "web-server";
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buildInputs = [ libxslt ];
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builder = builtins.toFile "builder.sh" "
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source $stdenv/setup
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mkdir $out
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echo "$servlets" | xsltproc ${stylesheet} - > $out/server-conf.xml ①
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";
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stylesheet = builtins.toFile "stylesheet.xsl" ②
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"<?xml version='1.0' encoding='UTF-8'?>
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<xsl:stylesheet xmlns:xsl='http://www.w3.org/1999/XSL/Transform' version='1.0'>
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<xsl:template match='/'>
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<Configure>
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<xsl:for-each select='/expr/list/attrs'>
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<Call name='addWebApplication'>
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<Arg><xsl:value-of select=\"attr[@name = 'path']/string/@value\" /></Arg>
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<Arg><xsl:value-of select=\"attr[@name = 'war']/path/@value\" /></Arg>
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</Call>
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</xsl:for-each>
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</Configure>
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</xsl:template>
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</xsl:stylesheet>
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";
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servlets = builtins.toXML [ ③
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{ path = "/bugtracker"; war = jira + "/lib/atlassian-jira.war"; }
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{ path = "/wiki"; war = uberwiki + "/uberwiki.war"; }
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];
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})
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```
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The builder is supposed to generate the configuration file for a
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[Jetty servlet container](http://jetty.mortbay.org/). A servlet
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container contains a number of servlets (`*.war` files) each
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exported under a specific URI prefix. So the servlet configuration
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is a list of sets containing the `path` and `war` of the servlet
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(①). This kind of information is difficult to communicate with the
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|
normal method of passing information through an environment
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variable, which just concatenates everything together into a
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string (which might just work in this case, but wouldn’t work if
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fields are optional or contain lists themselves). Instead the Nix
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expression is converted to an XML representation with `toXML`,
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which is unambiguous and can easily be processed with the
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appropriate tools. For instance, in the example an XSLT stylesheet
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(at point ②) is applied to it (at point ①) to generate the XML
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configuration file for the Jetty server. The XML representation
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produced at point ③ by `toXML` is as follows:
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```xml
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<?xml version='1.0' encoding='utf-8'?>
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<expr>
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<list>
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<attrs>
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<attr name="path">
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<string value="/bugtracker" />
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</attr>
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<attr name="war">
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<path value="/nix/store/d1jh9pasa7k2...-jira/lib/atlassian-jira.war" />
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</attr>
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</attrs>
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<attrs>
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<attr name="path">
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<string value="/wiki" />
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</attr>
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<attr name="war">
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<path value="/nix/store/y6423b1yi4sx...-uberwiki/uberwiki.war" />
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</attr>
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</attrs>
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</list>
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</expr>
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```
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Note that we used the `toFile` built-in to write the builder and
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the stylesheet “inline” in the Nix expression. The path of the
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stylesheet is spliced into the builder using the syntax `xsltproc
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${stylesheet}`.
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)",
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.fun = prim_toXML,
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});
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}
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