Fix xrefs (#402)

VERSION

@@ -1 +1 @@
-25
+26

flake-info/src/data/fix-xrefs.lua

@@ -0,0 +1,21 @@
+--[[
+Resolve cross-references to NixOS options in a hacky way and link them to the
+unstable channel's option search page on search.nixos.org
+]]
+
+function Link(elem)
+  prefix = '#opt-'
+  if elem.target:sub(1, #prefix) == prefix then
+    option_name = elem.target:sub(#prefix + 1)
+    option_name = option_name:gsub('%._name_%.', '.<name>.')
+    option_name = option_name:gsub('%._%.', '.*.')
+
+    elem.target = 'https://search.nixos.org/options?channel=unstable&show=' .. option_name .. '&query=' .. option_name
+
+    if #elem.content == 1 and elem.content[1].tag == 'Str' and elem.content[1].text == '???' then
+      elem.content[1].text = option_name
+    end
+
+    return elem
+  end
+end

flake-info/src/data/pandoc.rs

@@ -1,3 +1,5 @@
+use std::fs::File;
+use std::io::Write;
 use std::path::PathBuf;
 
 use lazy_static::lazy_static;
@@ -6,6 +8,8 @@ use pandoc::{
     InputFormat, InputKind, OutputFormat, OutputKind, PandocError, PandocOption, PandocOutput,
 };
 
+const XREF_FILTER: &str = include_str!("fix-xrefs.lua");
+
 lazy_static! {
     static ref FILTERS_PATH: PathBuf = std::env::var("NIXPKGS_PANDOC_FILTERS_PATH")
         .unwrap_or("".into())
@@ -35,6 +39,10 @@ impl<T: AsRef<str>> PandocExt for T {
             p.push("link-unix-man-references.lua");
             p
         };
+        let tmpdir = tempfile::tempdir()?;
+        let xref_filter = tmpdir.path().join("fix-xrefs.lua");
+        writeln!(File::create(&xref_filter)?, "{}", XREF_FILTER)?;
+
         let mut pandoc = pandoc::new();
         let wrapper_xml = format!(
             "
@@ -52,6 +60,7 @@ impl<T: AsRef<str>> PandocExt for T {
         pandoc.add_options(&[
             PandocOption::LuaFilter(citeref_filter),
             PandocOption::LuaFilter(man_filter),
+            PandocOption::LuaFilter(xref_filter),
         ]);
 
         pandoc.execute().map(|result| match result {