Check Related reading and the search index on the built site

_plugins/related_posts.rb

@@ -110,6 +110,18 @@ def self.normalise(tags)
   def self.sort_time(post)
     post[:date].respond_to?(:to_time) ? post[:date].to_time.to_i : 0
   end
+
+  # The hash `rank` and `adjacent` take, from a Jekyll post.
+  def self.meta(doc)
+    {
+      id: doc.url,
+      tags: doc.data["tags"],
+      categories: doc.data["categories"],
+      lang: doc.data["lang"],
+      translation_id: doc.data["translation_id"],
+      date: doc.data["date"]
+    }
+  end
 end
 
 # --- Jekyll wiring -----------------------------------------------------------
@@ -119,16 +131,7 @@ def self.sort_time(post)
 if defined?(Jekyll::Hooks)
   Jekyll::Hooks.register :site, :pre_render do |site|
     docs = site.posts.docs
-    meta = docs.map do |d|
-      {
-        id: d.url,
-        tags: d.data["tags"],
-        categories: d.data["categories"],
-        lang: d.data["lang"],
-        translation_id: d.data["translation_id"],
-        date: d.data["date"]
-      }
-    end
+    meta = docs.map { |d| RelatedPosts.meta(d) }
     by_url = docs.to_h { |d| [d.url, d] }
     # Sorted here rather than trusting the collection's order, and by id as well
     # as date so posts with the same timestamp keep one order on every build.

script/check-plugin-output.rb

@@ -1,9 +1,10 @@
 # frozen_string_literal: true
 #
 # Checks that the _plugins/ hooks that change a post's page left their mark,
-# that kramdown parsed the post's block HTML, that no listing shows a
-# translation beside its original, that every cover is credited on its page,
-# that no page repeats an id, and that the feed has room for every post.
+# that the search index parses and holds every post, that kramdown parsed the
+# post's block HTML, that no listing shows a translation beside its original,
+# that every cover is credited on its page, that no page repeats an id, and
+# that the feed has room for every post.
 #
 # test/ covers the plugins' functions, not the Jekyll hooks that apply them, and
 # with a hook gone the build still passes. Jekyll itself reads the posts here,
@@ -14,6 +15,7 @@
 # Prints one line per problem; exits 1 when there is any.
 
 require "jekyll"
+require "json"
 
 site_dir = File.expand_path(ARGV.fetch(0))
 root = File.expand_path("..", __dir__)
@@ -31,6 +33,7 @@
 problems = []
 lang = ->(post) { post.data["lang"] || site.config["lang"] }
 per_lang = posts.group_by(&lang).transform_values(&:size)
+metas = posts.map { |p| RelatedPosts.meta(p) }
 # Where Jekyll writes a URL: a directory one to index.html, a bare one to .html.
 built = lambda do |url|
   file = url.end_with?("/") ? "#{url}index.html" : File.extname(url).empty? ? "#{url}.html" : url
@@ -42,6 +45,17 @@
 # of an old paper never reaches it.
 problems << "feed.posts_limit is #{limit} for #{posts.size} posts; raise it in _config.yml" if posts.size > limit
 
+# search.json, with search_index.rb's plain_text: an index that does not parse
+# leaves js/search.js finding nothing, and saying nothing either.
+index = begin
+  JSON.parse(File.read(File.join(site_dir, "search.json")))
+rescue SystemCallError, JSON::ParserError
+  nil
+end
+unless index.is_a?(Array) && index.size == posts.size && index.all? { |e| e["url"] && !e["content"].to_s.strip.empty? }
+  problems << "search.json is not a list of every post with its url and text"
+end
+
 posts.each do |post|
   name = File.basename(post.path)
   path = built.call(post.url)
@@ -63,10 +77,14 @@
     end
   end
 
-  # related_posts.rb: previous/next links, given another post in the language.
+  # related_posts.rb: previous/next links, given another post in the language,
+  # and Related reading, given a post it ranks.
   if per_lang[lang.call(post)] > 1 && !html.include?(%(class="post-nav"))
     problems << "#{name}: no previous/next links"
   end
+  if RelatedPosts.rank(RelatedPosts.meta(post), metas).any? && !html.include?(%(class="related-posts"))
+    problems << "#{name}: no Related reading"
+  end
 
   imgs = html.scan(/<img\b[^>]*>/)
   # lazy_images.rb