internal/api/ratelimit_test.go

@@ -166,8 +166,11 @@ func TestHighlightCode(t *testing.T) {
 	if plain != "<b>x</b>" {
 		t.Fatalf("plain escaping wrong: %q", plain)
 	}
-	// line count preserved (gutter alignment)
+	// #205: newline join preserved as the delimiter paste-lines.js splits on;
-	if got := len(splitLines(lang.HighlightCode("a\nb\nc", "go"))); got != 3 {
+	// per-line segments survive and the client joins with '' so no newline
+	// text node reaches the rendered DOM.
+	hl := lang.HighlightCode("a\nb\nc", "go")
+	if got := len(splitLines(hl)); got != 3 {
 		t.Fatalf("want 3 lines, got %d", got)
 	}
 }

internal/lang/highlight.go

@@ -146,5 +146,9 @@ func HighlightCode(content, langID string) string {
 	for i, line := range lines {
 		out[i] = highlightLine(line, h, langID)
 	}
+	// Note: lines are joined with "\n" on purpose — paste-lines.js splits on
+	// the newline to build its per-line .codeline blocks, then joins those
+	// with "" and strips whitespace-only text nodes (#205), so no newline
+	// text node ever reaches the rendered DOM.
 	return strings.Join(out, "\n")
 }

internal/web/static/paste-lines.js

@@ -17,7 +17,10 @@
   // because HighlightCode highlights per line) in a .codeline block. The
   // spans are display:block, so they are joined with '' — a '\n' join leaves
   // newline text nodes between blocks that pre-wrap renders as an extra line
-  // box per line, which would shift every following number down one row (#167).
+  // box per line, which would shift every following number down one row (#167,
+  // #205). Whitespace-only text nodes are also stripped defensively below: any
+  // that reach the DOM (older cached HTML, other templates) render as phantom
+  // rows under white-space: pre and drift the gutter.
   function splitLines() {
     var html = body.innerHTML;
     var parts = html.split('\n');
@@ -26,6 +29,12 @@
       out.push('<span class="codeline">' + parts[i] + '</span>');
     }
     body.innerHTML = out.join('');
+    // #205: strip whitespace-only text nodes between the .codeline blocks.
+    var ws = [];
+    for (var n = body.firstChild; n; n = n.nextSibling) {
+      if (n.nodeType === 3 && !/\S/.test(n.nodeValue)) ws.push(n);
+    }
+    for (var w = 0; w < ws.length; w++) body.removeChild(ws[w]);
   }
 
   // One .gutline block per visual row. The gutter must reproduce the code