From d1f1f481d099f7b2dc22f55d584581317b2158a0 Mon Sep 17 00:00:00 2001 From: Anders Kaseorg Date: Sat, 3 Oct 2026 23:56:19 +0000 Subject: [PATCH 1/2] Preserve whitespace when serializing without indentation The serializer dropped whitespace-only text nodes and trimmed trailing whitespace from all other text nodes, regardless of the indent setting. Even with indent=0, this changed the meaning of the document: "a b" serialized as "ab", and 
, ",
+            markupever.HtmlOptions(full_document=False),
+        ),
+        (
+            "",
+            markupever.HtmlOptions(full_document=False),
+        ),
+        (" x \n  \t", markupever.XmlOptions()),
+    ]:
+        dom = markupever.parse(content, options)
+        assert dom.serialize(indent=0) == content
+
+
 def test_add_itself():
     tag = markupever.parse("
").root().first_child
 
diff --git a/treedom/src/dom.rs b/treedom/src/dom.rs
index fff86d1..63c962f 100644
--- a/treedom/src/dom.rs
+++ b/treedom/src/dom.rs
@@ -230,7 +230,10 @@ impl<'a> Serializer<'a> {
                         serializer.write_processing_instruction(&pi.target, &pi.data)?
                     }
                     interface::Interface::Text(text) => {
-                        if !text.contents.trim_ascii().is_empty() {
+                        // Without indentation, whitespace is significant: write it unchanged.
+                        if self.indent == 0 {
+                            serializer.write_text(&text.contents)?;
+                        } else if !text.contents.trim_ascii().is_empty() {
                             serializer.write_text(text.contents.trim_ascii_end())?;
                         }
                     }
diff --git a/treedom/src/parser.rs b/treedom/src/parser.rs
index 76a5848..3e2d6b7 100644
--- a/treedom/src/parser.rs
+++ b/treedom/src/parser.rs
@@ -579,6 +579,27 @@ mod tests {
         assert_eq!(HTML, String::from_utf8_lossy(&buf));
     }
 
+    #[cfg(feature = "html5ever")]
+    #[test]
+    fn html_serializer_preserves_whitespace() {
+        use crate::Serializer;
+
+        const HTML: &str = "\n\n
a b
\n
  x\n\n
\n";
+
+        let parser = ParserSink::parse_html(true, Default::default(), Default::default());
+        let dom = parser.one(HTML).into_dom();
+
+        let mut buf: Vec = Vec::new();
+        html5ever::serialize::serialize(
+            &mut buf,
+            &Serializer::new(&dom, dom.root().id(), 0),
+            Default::default(),
+        )
+        .unwrap();
+
+        assert_eq!(HTML, String::from_utf8_lossy(&buf));
+    }
+
     #[cfg(feature = "xml5ever")]
     #[test]
     fn xml_serializer() {

From 977fae6e77d247980b3029a1052f3b233b5a9cfb Mon Sep 17 00:00:00 2001
From: Anders Kaseorg 
Date: Mon, 5 Oct 2026 10:59:10 +0000
Subject: [PATCH 2/2] Serialize without indentation by default

serialize() and serialize_bytes() pretty-printed with indent=4 by
default, which adds and removes whitespace and so can change the
meaning of the document: it changes the rendering of whitespace
between inline elements, and the contents of 
,