Don't modify headers or dt if the tag is manually written HTML

This changes it so that header and `<dt>` tags manually written as HTML
are not modified (no anchor, no id, etc.). This is to avoid mangling any
HTML that the user explicitly crafted.

I'm not sure what the fallout from the headers might be, since I'm not
100% sure there aren't uses where the user wanted mdbook to modify
manual HTML. However, I don't see any in rust-lang's use.

crates/mdbook-html/src/html/tree.rs

@@ -77,6 +77,8 @@ pub(crate) struct Element {
     pub(crate) attrs: Attributes,
     /// True if this tag ends with `/>`.
     pub(crate) self_closing: bool,
+    /// True if this was raw HTML written in the markdown.
+    pub(crate) was_raw: bool,
 }
 
 impl Element {
@@ -87,6 +89,7 @@ impl Element {
             name,
             attrs: Attributes::new(),
             self_closing: false,
+            was_raw: false,
         }
     }
 
@@ -618,6 +621,7 @@ where
                                 name,
                                 attrs,
                                 self_closing: tag.self_closing,
+                                was_raw: true,
                             };
                             fix_html_link(&mut el);
                             self.push(Node::Element(el));
@@ -842,6 +846,11 @@ where
         for heading in headings {
             let node = self.tree.get(heading).unwrap();
             let el = node.value().as_element().unwrap();
+            // Don't modify tags if they were manually written HTML. The
+            // user probably had some intent, and we don't want to mess it up.
+            if el.was_raw {
+                continue;
+            }
             let href = if let Some(id) = el.attr("id") {
                 format!("#{id}")
             } else {

tests/testsuite/markdown/basic_markdown/expected/html.html

@@ -64,6 +64,6 @@ const x = 'some *text* inside';
 .bar { background-color: green }
 </style>
 <h2 id="manual-headers"><a class="header" href="#manual-headers">Manual headers</a></h2>
-<h2 id="my header"><a class="header" href="#my header"><a href="#foo">My Header</a></a></h2>
+<h2 id="my header"><a href="#foo">My Header</a></h2>
 
-<h3 id="another-header"><a class="header" href="#another-header">Another header</a></h3>
+<h3>Another header</h3>

tests/testsuite/markdown/definition_lists/expected/html_definition_lists.html

@@ -2,13 +2,13 @@
 <p>Test for definition lists manually written in HTML.</p>
 <dl>
     
-<dt id="some-tag"><a class="header" href="#some-tag">Some tag</a></dt>
+<dt>Some tag</dt>
 
     
 <dd>Some defintion</dd>
 
     
-<dt class="myclass" id="myid"><a class="header" href="#myid"><a class="option-anchor" href="#foo">Another definition</a></a></dt>
+<dt class="myclass" id="myid"><a class="option-anchor" href="#foo">Another definition</a></dt>
 
     
 <dd class="def-class">A definition.</dd>

tests/testsuite/markdown/definition_lists/expected_disabled/html_definition_lists.html

@@ -2,13 +2,13 @@
 <p>Test for definition lists manually written in HTML.</p>
 <dl>
     
-<dt id="some-tag"><a class="header" href="#some-tag">Some tag</a></dt>
+<dt>Some tag</dt>
 
     
 <dd>Some defintion</dd>
 
     
-<dt class="myclass" id="myid"><a class="header" href="#myid"><a class="option-anchor" href="#foo">Another definition</a></a></dt>
+<dt class="myclass" id="myid"><a class="option-anchor" href="#foo">Another definition</a></dt>
 
     
 <dd class="def-class">A definition.</dd>