Handle pre elements that start with a newline

1 files changed, 17 insertions, 0 deletions

diff --git a/crates/typst-html/src/encode.rs b/crates/typst-html/src/encode.rs
index 2bfa78a7..82a5df47 100644
--- a/crates/typst-html/src/encode.rs
+++ b/crates/typst-html/src/encode.rs
@@ -97,6 +97,11 @@ fn write_element(w: &mut Writer, element: &HtmlElement) -> SourceResult<()> {
 
     let pretty = w.pretty;
     if !element.children.is_empty() {
+        // See HTML spec § 13.1.2.5.
+        if element.tag == tag::pre && starts_with_newline(element) {
+            w.buf.push('\n');
+        }
+
         let pretty_inside = allows_pretty_inside(element.tag)
             && element.children.iter().any(|node| match node {
                 HtmlNode::Element(child) => wants_pretty_around(child.tag),
@@ -133,6 +138,18 @@ fn write_element(w: &mut Writer, element: &HtmlElement) -> SourceResult<()> {
     Ok(())
 }
 
+/// Whether the first character in the element is a newline.
+fn starts_with_newline(element: &HtmlElement) -> bool {
+    for child in &element.children {
+        match child {
+            HtmlNode::Tag(_) => {}
+            HtmlNode::Text(text, _) => return text.starts_with(['\n', '\r']),
+            _ => return false,
+        }
+    }
+    false
+}
+
 /// Whether we are allowed to add an extra newline at the start and end of the
 /// element's contents.
 ///