Adapt StaticFile for collections, config defaults

This enables files such as images and PDFs to show up in the same relative
output directory as other HTML and Markdown documents in the same collection.

It also enables static files to be hidden using defaults from _config.yml in
the same way that other documents in the same collection and directories may
be hidden using `published: false`.

lib/jekyll/static_file.rb

@@ -37,7 +37,7 @@ def destination(dest)
 
     def destination_rel_dir
       if @collection
-        @dir.gsub(/\A_/, '')
+        File.dirname(url)
       else
         @dir
       end
@@ -61,9 +61,10 @@ def modified?
 
     # Whether to write the file to the filesystem
     #
-    # Returns true.
+    # Returns true unless the defaults for the destination path from
+    # _config.yml contain `published: false`.
     def write?
-      true
+      defaults.fetch('published', true)
     end
 
     # Write the static file to the destination directory (if modified).
@@ -100,5 +101,41 @@ def to_liquid
         "path"          => File.join("", relative_path)
       }
     end
+
+    def placeholders
+      {
+        collection: @collection.label,
+        path: relative_path[
+          @collection.relative_directory.size..relative_path.size],
+        output_ext: '',
+        name: '',
+        title: '',
+      }
+    end
+
+    # Applies a similar URL-building technique as Jekyll::Document that takes
+    # the collection's URL template into account. The default URL template can
+    # be overriden in the collection's configuration in _config.yml.
+    def url
+      @url ||= if @collection.nil?
+        relative_path
+      else
+        ::Jekyll::URL.new({
+          template:  @collection.url_template,
+          placeholders: placeholders,
+        })
+      end.to_s.gsub /\/$/, ''
+    end
+
+    # Returns the type of the collection if present, nil otherwise.
+    def type
+      @type ||= @collection.nil? ? nil : @collection.label.to_sym
+    end
+
+    # Returns the front matter defaults defined for the file's URL and/or type
+    # as defined in _config.yml.
+    def defaults
+      @defaults ||= @site.frontmatter_defaults.all url, type
+    end
   end
 end

test/test_static_file.rb

@@ -18,6 +18,16 @@ def setup_static_file(base, dir, name)
     StaticFile.new(@site, base, dir, name)
   end
 
+  def setup_static_file_with_collection(base, dir, name, label, metadata)
+    site = fixture_site 'collections' => {label => metadata}
+    StaticFile.new(site, base, dir, name, site.collections[label])
+  end
+
+  def setup_static_file_with_defaults(base, dir, name, defaults)
+    site = fixture_site 'defaults' => defaults
+    StaticFile.new(site, base, dir, name)
+  end
+
   context "A StaticFile" do
     setup do
       clear_dest
@@ -46,7 +56,44 @@ def setup_static_file(base, dir, name)
 
     should "have a destination relative directory without a collection" do
       static_file = setup_static_file("root", "dir/subdir", "file.html")
-      assert "dir/subdir", static_file.destination_rel_dir
+      assert_equal nil, static_file.type
+      assert_equal "dir/subdir/file.html", static_file.url
+      assert_equal "dir/subdir", static_file.destination_rel_dir
+    end
+
+    should "have a destination relative directory with a collection" do
+      static_file = setup_static_file_with_collection(
+        "root", "_foo/dir/subdir", "file.html", "foo", {"output" => true})
+      assert_equal :foo, static_file.type
+      assert_equal "/foo/dir/subdir/file.html", static_file.url
+      assert_equal "/foo/dir/subdir", static_file.destination_rel_dir
+    end
+
+    should "use its collection's permalink template for the destination relative directory" do
+      static_file = setup_static_file_with_collection(
+        "root", "_foo/dir/subdir", "file.html", "foo",
+        {"output" => true, "permalink" => "/:path/"})
+      assert_equal :foo, static_file.type
+      assert_equal "/dir/subdir/file.html", static_file.url
+      assert_equal "/dir/subdir", static_file.destination_rel_dir
+    end
+
+    should "be writable by default" do
+      static_file = setup_static_file("root", "dir/subdir", "file.html")
+      assert(static_file.write?,
+        "static_file.write? should return true by default")
+    end
+
+    should "use the _config.yml defaults to determine writability" do
+      defaults = [{
+        "scope" => {"path" => "private"},
+        "values" => {"published" => false}
+      }]
+      static_file = setup_static_file_with_defaults(
+        "root", "private/dir/subdir", "file.html", defaults)
+      assert(!static_file.write?,
+        "static_file.write? should return false when _config.yml sets " +
+        "`published: false`")
     end
 
     should "know its last modification time" do