fix: align SSR and client text whitespace

crates/webui-parser/benches/parser_bench.rs

@@ -625,6 +625,34 @@ fn client_template_directives_bench(c: &mut Criterion) {
     });
 }
 
+fn client_template_whitespace_bench(c: &mut Criterion) {
+    let lf = format!(
+        "<section>{}</section>",
+        "\n  <button>\n    {{label}}\n  </button>".repeat(100)
+    );
+    let mut group = c.benchmark_group("client_template_whitespace");
+    for (name, input) in [
+        ("lf_100", lf.clone()),
+        ("crlf_100", lf.replace('\n', "\r\n")),
+        (
+            "entities_100",
+            lf.replace("{{label}}", "&lt; {{label}} &amp;"),
+        ),
+    ] {
+        group.throughput(Throughput::Bytes(input.len() as u64));
+        group.bench_with_input(name, &input, |b, html| {
+            b.iter(|| {
+                webui_parser::plugin::webui::generate_compiled_template(
+                    "bench-whitespace",
+                    black_box(html),
+                )
+                .unwrap_or_else(|error| panic!("client text compilation failed: {error}"))
+            });
+        });
+    }
+    group.finish();
+}
+
 fn parser_isolated_bench(c: &mut Criterion) {
     let mut group = c.benchmark_group("parser_isolated");
     for (name, input) in [
@@ -682,6 +710,7 @@ criterion_group!(
     parser_text_vs_directive_bench,
     parser_adversarial_bench,
     client_template_directives_bench,
+    client_template_whitespace_bench,
     parser_isolated_bench,
     css_token_analysis_bench
 );

crates/webui-parser/src/lib.rs

@@ -3943,9 +3943,9 @@ impl HtmlParser {
         let parsed_fragments = self.handlebars_parser.parse(content)?;
         for fragment in parsed_fragments {
             if let Some(Fragment::Raw(raw)) = fragment.fragment.as_ref() {
-                if Self::should_emit_text_content(&raw.value) {
-                    self.add_raw_fragment(&raw.value);
-                }
+                // Whitespace inside an emitted text run is part of the binding,
+                // not inter-element formatting. Client text parts retain it too.
+                self.add_raw_fragment(&raw.value);
             } else if let Some(Fragment::Signal(signal)) = fragment.fragment.as_ref() {
                 if signal.raw && is_html_text_only_scope(self.boundary_parent_scope) {
                     self.add_fragment(
@@ -5761,6 +5761,28 @@ mod tests {
         );
     }
 
+    #[test]
+    fn test_parse_preserves_whitespace_inside_bound_text_runs() -> Result<()> {
+        let mut parser = HtmlParser::new();
+        parser.parse(
+            "test.html",
+            "\n  <button>\n    {{title}}\n  </button>\n  <pre>  {{details}}\n  </pre>\n",
+        )?;
+        let records = parser.into_fragment_records();
+        assert_stream!(
+            records,
+            "test.html",
+            [
+                raw("<button>\n    "),
+                signal("title"),
+                raw("\n  </button><pre>  "),
+                signal("details"),
+                raw("\n  </pre>"),
+            ]
+        );
+        Ok(())
+    }
+
     #[test]
     fn test_invalid_for_each_is_template_diagnostic() {
         let mut parser = HtmlParser::new();
@@ -6697,7 +6719,15 @@ mod tests {
             [for_loop("item", "category.items", "for-2"),]
         );
 
-        assert_stream!(fragment_records, "for-2", [signal("item.title"),]);
+        assert_stream!(
+            fragment_records,
+            "for-2",
+            [
+                raw("\n                   "),
+                signal("item.title"),
+                raw("\n                "),
+            ]
+        );
     }
 
     #[test]