I'm maybe making a huge mistake

Magic comments? Who needs them! I'm going to lean hard into html and
write some server-side custom elements. Here goes nothing.

Write some tests. Make them pass.

lib/magic_comment_hydrator.rb

@@ -15,7 +15,11 @@ def hydrate
 
   def next_magic_comment
     magic_comment_regex = /<!--(Include|IncludeInHeader)::(.*?)-->/m
-    content.match(magic_comment_regex)
+    eval_ruby_regex = %r{<(eval-ruby)>(.*?)</eval-ruby>}m
+    include_in_header_regex =
+      %r{<(include-in-header)>(.*?)</include-in-header>}m
+    content.match(magic_comment_regex) || content.match(eval_ruby_regex) ||
+      content.match(include_in_header_regex)
   end
 
   def next
@@ -25,20 +29,33 @@ def next
 
     insert_at =
       case current_magic_comment[1]
-      when "IncludeInHeader"
+      when "IncludeInHeader", "include-in-header"
         content.index("</head>")
-      when "Include"
+      when "Include", "eval-ruby"
         content.index(current_magic_comment[0])
       else
         fail "Don't know how to handle #{current_magic_comment[1]}"
       end
 
-    includable, maybe_string = current_magic_comment[2].split(/\s/m, 2)
     replacement =
-      includables
-        .fetch(includable)
-        .new(string: maybe_string.to_s.strip, data: data)
-        .render
+      case current_magic_comment[1]
+      when "eval-ruby"
+        begin
+          eval(current_magic_comment[2]).to_s.strip
+        end
+      when "include-in-header"
+        current_magic_comment[2].to_s.strip
+      when "IncludeInHeader", "Include"
+        includable, maybe_string = current_magic_comment[2].split(/\s/m, 2)
+
+        includables
+          .fetch(includable)
+          .new(string: maybe_string.to_s.strip, data: data)
+          .render
+          .to_s
+      else
+        fail "Don't know how to handle #{current_magic_comment[1]}"
+      end
 
     next_content =
       content.sub(current_magic_comment[0], "").insert(insert_at, replacement)

site/index.md

@@ -10,3 +10,6 @@ You can subscribe to [Dan Ott's Website RSS Feed](/feed.xml).
 Here's a list of posts I've written in reverse chronological order.
 
 <!--Include::Index-->
+<eval-ruby>
+  Includable::Index.new(string: nil, data: Build.data)
+</eval-ruby>

site/javascripts/script.js

@@ -1,3 +1,16 @@
 /* @format */
 
 console.log("Hello World!");
+
+class IncludeHere extends HTMLElement {
+  connectedCallback() {
+    console.error("Unexpected Custom element added to page!");
+    console.error(this);
+    this.parentElement.removeChild(this);
+  }
+}
+
+class IncludeInHeader extends IncludeHere {}
+
+customElements.define("include-in-header", IncludeInHeader);
+customElements.define("eval-ruby", IncludeHere);

test/magic_comment_hydrator_test.rb

@@ -13,6 +13,14 @@ class MagicCommentHydratorTest < Minitest::Test
         <h1>Test</h1>
         <!--Include::DummyIntendedForInline-->
         <!--Include::HydraIncludable-->
+
+        <h2><eval-ruby>2 + 2</eval-ruby></h2>
+
+        <include-in-header>
+          <meta name="include-in-header">
+          <eval-ruby>'<meta name="eval-ruby"' + ">"</eval-ruby>
+        </include-in-header>
+
       </body>
     </html>
   HTML
@@ -51,6 +59,16 @@ def test_everything
                    .content
                    .scan("<h1>DummyIntendedForInline Return that!</h1>")
                    .size
+
+    refute_includes result.content, "<eval-ruby>2 + 2</eval-ruby>"
+    assert_includes result.content, "<h2>4</h2>"
+
+    refute_includes result.content, "<include-in-header>"
+    assert_includes result.content, '<meta name="include-in-header">'
+    assert_includes result.content, '<meta name="eval-ruby">'
+    assert result.content.index('name="eval-ruby"') <
+             result.content.index("</head>"),
+           "Should actually be injected into the head!"
   end
 
   class DummyIntendedForInline