Fix duplicate descriptions bug

jeremyroman · web-flow · commit 0334e03ea73e · 2023-10-31T15:44:56.000+09:00
Various attributes (with IDs matching patterns such as attr-dim-*, attr-fae-*, attr-fe-*, and attr-media-*) have duplicate definition links (for various elements they apply to) which were being concatenated as though they were multiple distinct descriptions. These shouldn't be duplicated (these descriptions are by definition identical). This was a regression introduced in the Rust preprocessor rewrite of 24db54a. Fixes whatwg/html#9889.
diff --git a/src/annotate_attributes.rs b/src/annotate_attributes.rs
@@ -1,6 +1,6 @@
 //! Augments the content attribute list for each element with a description found in the Attributes table.
 
-use std::collections::HashMap;
+use std::collections::{HashMap, HashSet};
 use std::io;
 use std::rc::Rc;
 
@@ -116,6 +116,11 @@ impl Processor {
                 _ => continue,
             };
 
+            // If a single row describes the same element multiple times, we don't need to repeat it.
+            // StrTendril doesn't have logical interior mutability, so this Clippy warning is overzealous.
+            #[allow(clippy::mutable_key_type)]
+            let mut seen_this_row: HashSet<StrTendril> = HashSet::new();
+
             // These will be strings like "attr-input-maxlength", which identify particular element-attribute pairs.
             let data_x = QualName::new(None, ns!(), LocalName::from("data-x"));
             for attr_key in keys_td
@@ -124,6 +129,14 @@ impl Processor {
                 .iter()
                 .filter_map(|c| c.get_attribute(&data_x).filter(|v| !v.is_empty()))
             {
+                // If this row describes the the same attribute, with the same
+                // identifier, for multiple elements (like attr-fae-form and
+                // attr-dim-width), these aren't actually distinct descriptions
+                // and we need not join them.
+                if !seen_this_row.insert(attr_key.clone()) {
+                    continue;
+                }
+
                 // Find the <!-- or: --> comment, if one exists, and extract its contents.
                 let description = description_td.children.borrow();
                 let mut variant_comment = None;
@@ -463,6 +476,54 @@ mod tests {
 <table id="attributes-1"><tbody>
     <tr><th><code data-x="">name</code></th><td><code data-x="attr-a-name">a</code></td><td>Anchor name
     </td></tr><tr><th><code data-x="">name</code></th><td><code data-x="attr-a-name">a</code></td><td>Name of the anchor
+</td></tr></tbody></table></body></html>
+            "#.trim()
+        );
+        Ok(())
+    }
+
+    #[tokio::test]
+    async fn test_identical_links() -> io::Result<()> {
+        // This checks the same identifier can be linked multiple times without
+        // repeating the description.
+        let document = parse_document_async(
+            r#"
+<h3>The img element</h3>
+<dl class="element">
+    <dt><span data-x="concept-element-attributes">Content attributes</span>
+    <dd><code data-x="attr-dim-width">width</code>
+</dl>
+<h3>The video element</h3>
+<dl class="element">
+    <dt><span data-x="concept-element-attributes">Content attributes</span>
+    <dd><code data-x="attr-dim-width">width</code>
+</dl>
+<h3>Attributes</h3>
+<table id="attributes-1"><tbody>
+    <tr><th><code data-x>width</code><td><code data-x="attr-dim-width">img</code>; <code data-x="attr-dim-width">video</code><td>Horizontal dimension
+</tbody></table>
+            "#.trim().as_bytes()).await?;
+        let mut proc = Processor::new();
+        dom_utils::scan_dom(&document, &mut |h| proc.visit(h));
+        proc.apply().await?;
+        assert_eq!(
+            serialize_for_test(&[document]),
+            r#"
+<html><head></head><body><h3>The img element</h3>
+<dl class="element">
+    <dt><span data-x="concept-element-attributes">Content attributes</span>
+    </dt><dd><code data-x="attr-dim-width">width</code>
+ — Horizontal dimension
+</dd></dl>
+<h3>The video element</h3>
+<dl class="element">
+    <dt><span data-x="concept-element-attributes">Content attributes</span>
+    </dt><dd><code data-x="attr-dim-width">width</code>
+ — Horizontal dimension
+</dd></dl>
+<h3>Attributes</h3>
+<table id="attributes-1"><tbody>
+    <tr><th><code data-x="">width</code></th><td><code data-x="attr-dim-width">img</code>; <code data-x="attr-dim-width">video</code></td><td>Horizontal dimension
 </td></tr></tbody></table></body></html>
             "#.trim()
         );
