Properly handle whitespace around comments (fixes #79)

askama_derive/src/generator.rs

@@ -310,7 +310,9 @@ impl<'a> Generator<'a> {
                 Node::Lit(lws, val, rws) => {
                     self.write_lit(lws, val, rws);
                 },
-                Node::Comment() => {},
+                Node::Comment(ref ws) => {
+                    self.write_comment(ws);
+                },
                 Node::Expr(ref ws, ref val) => {
                     self.write_expr(state, ws, val);
                 },
@@ -600,6 +602,10 @@ impl<'a> Generator<'a> {
         }
     }
 
+    fn write_comment(&mut self, ws: &WS) {
+        self.handle_ws(ws);
+    }
+
     /* Visitor methods for expression types */
 
     fn visit_expr_root(&mut self, expr: &Expr) -> DisplayWrap {

askama_derive/src/parser.rs

@@ -52,7 +52,7 @@ pub struct Macro<'a> {
 #[derive(Debug)]
 pub enum Node<'a> {
     Lit(&'a str, &'a str, &'a str),
-    Comment(),
+    Comment(WS),
     Expr(WS, Expr<'a>),
     Call(WS, Option<& 'a str>, &'a str, Vec<Expr<'a>>),
     LetDecl(WS, Target<'a>),
@@ -638,9 +638,10 @@ named!(block_node<Node>, do_parse!(
 
 named!(block_comment<Node>, do_parse!(
     tag_s!("{#") >>
-    take_until_s!("#}") >>
+    pws: opt!(tag_s!("-")) >>
+    inner: take_until_s!("#}") >>
     tag_s!("#}") >>
-    (Node::Comment())
+    (Node::Comment(WS(pws.is_some(), inner.len() > 1 && inner[inner.len() - 1] == b'-')))
 ));
 
 named!(parse_template<Vec<Node<'a>>>, many0!(alt!(

testing/tests/simple.rs

@@ -196,3 +196,14 @@ fn test_slice_literal() {
     let t = ArrayTemplate {};
     assert_eq!(t.render().unwrap(), "a");
 }
+
+
+#[derive(Template)]
+#[template(source = "  {# foo -#} ", ext = "txt")]
+struct CommentTemplate {}
+
+#[test]
+fn test_comment() {
+    let t = CommentTemplate {};
+    assert_eq!(t.render().unwrap(), "  ");
+}