Add a table sticky headings filter

This wraps all tables inside a div with a class of
table-sticky-headings, so that we can style them.

See https://gitlab.com/gitlab-org/gitlab-docs/-/issues/1076

1 files changed, 25 insertions, 0 deletions

diff --git a/lib/filters/table_sticky_headings.rb b/lib/filters/table_sticky_headings.rb
new file mode 100644
index 00000000..13c0f63f
--- /dev/null
+++ b/lib/filters/table_sticky_headings.rb
@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+#
+# Wrap tables inside a div so we can apply CSS styles to them
+# https://gitlab.com/gitlab-org/gitlab-docs/-/issues/1076
+#
+class TableStickyHeadings < Nanoc::Filter
+  identifier :table_sticky_headings
+
+  def run(content, params = {})
+    # `#dup` is necessary because `.fragment` modifies the incoming string. Ew!
+    # See https://github.com/sparklemotion/nokogiri/issues/1077
+    doc = Nokogiri::HTML.fragment(content.dup)
+    doc.css('table').each do |table|
+      content = table.to_html
+      new_content = generate(content)
+      table.replace(new_content)
+    end
+    doc.to_s
+  end
+
+  def generate(content)
+    %(<div class="table-sticky-headings">#{content}</div>)
+  end
+end