jekyll · goulvench · Nov 14, 2018 · Nov 17, 2018 · Feb 6, 2019 · Feb 6, 2019
diff --git a/README.md b/README.md
@@ -120,6 +120,10 @@ There are several ways to convey author-specific information. Author information
 
 The plugin exposes a helper tag to expose the appropriate meta tags to support automated discovery of your feed. Simply place `{% feed_meta %}` someplace in your template's `<head>` section, to output the necessary metadata.
 
+The helper can also generate the link for a given collection: `{% feed_meta my_collection %}` or a given category: `{% feed_meta my_collection my_category %}`.
+
+To generate links for every collections and categories, call the helper using this syntax: `{% feed_meta include: all %}`.
+
 ### SmartyPants
 
 The plugin uses [Jekyll's `smartify` filter](https://jekyllrb.com/docs/templates/) for processing the site title and post titles. This will translate plain ASCII punctuation into "smart" typographic punctuation. This will not render or strip any Markdown you may be using in a title.

diff --git a/lib/jekyll-feed/generator.rb b/lib/jekyll-feed/generator.rb
@@ -19,19 +19,6 @@ def generate(site)
       end
     end
 
-    private
-
-    # Matches all whitespace that follows
-    #   1. A '>', which closes an XML tag or
-    #   2. A '}', which closes a Liquid tag
-    # We will strip all of this whitespace to minify the template
-    MINIFY_REGEX = %r!(?<=>|})\s+!.freeze
-
-    # Returns the plugin's config or an empty hash if not set
-    def config
-      @config ||= @site.config["feed"] || {}
-    end
-
     # Determines the destination path of a given feed
     #
     # collection - the name of a collection, e.g., "posts"
@@ -45,7 +32,7 @@ def feed_path(collection: "posts", category: nil)
       prefix = collection == "posts" ? "/feed" : "/feed/#{collection}"
       return "#{prefix}/#{category}.xml" if category
 
-      collections.dig(collection, "path") || "#{prefix}.xml"
+      @collections.dig(collection, "path") || "#{prefix}.xml"
     end
 
     # Returns a hash representing all collections to be processed and their metadata
@@ -69,6 +56,19 @@ def collections
       @collections
     end
 
+    private
+
+    # Matches all whitespace that follows
+    #   1. A '>', which closes an XML tag or
+    #   2. A '}', which closes a Liquid tag
+    # We will strip all of this whitespace to minify the template
+    MINIFY_REGEX = %r!(?<=>|})\s+!.freeze
+
+    # Returns the plugin's config or an empty hash if not set
+    def config
+      @config ||= @site.config["feed"] || {}
+    end
+
     # Path to feed.xml template file
     def feed_source_path
       @feed_source_path ||= File.expand_path "feed.xml", __dir__

diff --git a/lib/jekyll-feed/meta-tag.rb b/lib/jekyll-feed/meta-tag.rb
@@ -5,10 +5,29 @@ class MetaTag < Liquid::Tag
     # Use Jekyll's native relative_url filter
     include Jekyll::Filters::URLFilters
 
+    def initialize(tag_name, args, tokens)
+      super
+      @args = args.strip
+    end
+
     def render(context)
       @context = context
-      attrs    = attributes.map { |k, v| %(#{k}="#{v}") }.join(" ")
-      "<link #{attrs} />"
+      @collection = nil
+      @category   = nil
+
+      if @args == "include: all"
+        links = []
+        generator.collections.each do |collection, meta|
+          (meta["categories"] + [nil]).each do |category|
+            links << link(collection, category)
+          end
+        end
+        links.reverse.join "\n"
+      else
+        @collection, @category = @args.split(" ")
+        @collection ||= "posts"
+        link(@collection, @category) if valid_collection && valid_category
+      end
     end
 
     private
@@ -17,21 +36,52 @@ def config
       @config ||= @context.registers[:site].config
     end
 
-    def attributes
+    def generator
+      @generator ||= @context.registers[:site].generators.find do |generator|
+        generator.is_a? JekyllFeed::Generator
+      end
+    end
+
+    def link(collection, category)
+      attrs = attributes(collection, category).map { |k, v| %(#{k}="#{v}") }.join(" ")
+      "<link #{attrs} />"
+    end
+
+    def attributes(collection, category)
+      href = absolute_url(generator.feed_path(:collection => collection, :category => category))
       {
         :type  => "application/atom+xml",
         :rel   => "alternate",
-        :href  => absolute_url(path),
+        :href  => href,
         :title => title,
       }.keep_if { |_, v| v }
     end
 
-    def path
-      config.dig("feed", "path") || "feed.xml"
-    end
-
     def title
       config["title"] || config["name"]
     end
+
+    def valid_collection
+      return true if generator.collections.key? @collection
+
+      invalidate_with_warning("collection")
+    end
+
+    def valid_category
+      return true if @collection == "posts" || @category.nil?
+
+      collection = generator.collections[@collection]
+      return true if collection.key?("categories") && collection["categories"].include?(@category)
+
+      invalidate_with_warning("category")
+    end
+
+    def invalidate_with_warning(type)
+      Jekyll.logger.warn(
+        "Jekyll Feed:",
+        "Invalid #{type} name. Please review `{% feed_meta #{@args} %}`"
+      )
+      false
+    end
   end
 end
diff --git a/spec/jekyll-feed_spec.rb b/spec/jekyll-feed_spec.rb
@@ -313,6 +313,66 @@
     end
   end
 
+  context "selecting a particular collection" do
+    let(:overrides) do
+      {
+        "collections" => {
+          "collection" => {
+            "output" => true,
+          },
+        },
+        "feed"        => {
+          "collections" => {
+            "collection" => {
+              "categories" => ["news"],
+            },
+          },
+        },
+      }
+    end
+    let(:default_feed) { Liquid::Template.parse("{% feed_meta posts %}").render!(context, {}) }
+    let(:collection_feed) { Liquid::Template.parse("{% feed_meta collection %}").render!(context, {}) }
+    let(:category_feed) { Liquid::Template.parse("{% feed_meta collection news %}").render!(context, {}) }
+
+    it "renders the feed meta for the selected collection" do
+      default_feed_link    = '<link type="application/atom+xml" rel="alternate" href="http://example.org/feed.xml" title="My awesome site" />'
+      collection_feed_link = '<link type="application/atom+xml" rel="alternate" href="http://example.org/feed/collection.xml" title="My awesome site" />'
+      category_feed_link   = '<link type="application/atom+xml" rel="alternate" href="http://example.org/feed/collection/news.xml" title="My awesome site" />'
+      expect(default_feed).to eql(default_feed_link)
+      expect(collection_feed).to eql(collection_feed_link)
+      expect(category_feed).to eql(category_feed_link)
+    end
+  end
+
+  context "requesting all feed links" do
+    let(:overrides) do
+      {
+        "collections" => {
+          "collection" => {
+            "output" => true,
+          },
+        },
+        "feed"        => {
+          "collections" => {
+            "collection" => {
+              "categories" => ["news"],
+            },
+          },
+        },
+      }
+    end
+    let(:full_feed_meta) { Liquid::Template.parse("{% feed_meta include: all %}").render!(context, {}) }
+
+    it "renders the feed meta for all collections and categories" do
+      default_feed_link    = '<link type="application/atom+xml" rel="alternate" href="http://example.org/feed.xml" title="My awesome site" />'
+      collection_feed_link = '<link type="application/atom+xml" rel="alternate" href="http://example.org/feed/collection.xml" title="My awesome site" />'
+      category_feed_link   = '<link type="application/atom+xml" rel="alternate" href="http://example.org/feed/collection/news.xml" title="My awesome site" />'
+      expect(full_feed_meta).to include(default_feed_link)
+      expect(full_feed_meta).to include(collection_feed_link)
+      expect(full_feed_meta).to include(category_feed_link)
+    end
+  end
+
   context "feed stylesheet" do
     it "includes the stylesheet" do
       expect(contents).to include('<?xml-stylesheet type="text/xml" href="http://example.org/feed.xslt.xml"?>')