Add parsing of whitespace trimming

Signed-off-by: Marcel Müller <neikos@neikos.email>

src/parser/mod.rs

@@ -16,6 +16,7 @@ use winnow::combinator::eof;
 use winnow::combinator::not;
 use winnow::combinator::opt;
 use winnow::combinator::peek;
+use winnow::combinator::preceded;
 use winnow::combinator::repeat_till;
 use winnow::combinator::terminated;
 use winnow::combinator::trace;
@@ -201,6 +202,7 @@ pub enum TokenKind {
     Content,
     LeftDelim,
     RightDelim,
+    TrimWhitespace,
     WantsOutput,
     Ident,
     Whitespace,
@@ -286,6 +288,7 @@ impl TemplateToken {
         content => TokenKind::Content,
         left_delim => TokenKind::LeftDelim,
         right_delim => TokenKind::RightDelim,
+        trim_whitespace => TokenKind::TrimWhitespace,
         wants_output => TokenKind::WantsOutput,
         ident => TokenKind::Ident,
         whitespace => TokenKind::Whitespace,
@@ -344,9 +347,10 @@ fn parse_content<'input>(input: &mut Input<'input>) -> PResult<'input, Vec<Templ
 fn parse_interpolate<'input>(input: &mut Input<'input>) -> PResult<'input, Vec<TemplateToken>> {
     let prev_whitespace = opt(parse_whitespace).parse_next(input)?;
     let left_delim = "{{".map(TemplateToken::left_delim).parse_next(input)?;
+    let left_trim = opt("-".map(TemplateToken::trim_whitespace)).parse_next(input)?;
     let wants_output = opt("=".map(TemplateToken::wants_output)).parse_next(input)?;
 
-    let get_tokens = repeat_till(1.., parse_block_token, peek("}}"));
+    let get_tokens = repeat_till(1.., parse_block_token, peek(preceded(opt("-"), "}}")));
     let recover = take_until(0.., "}}").void();
 
     let (inside_tokens, _): (Vec<_>, _) = get_tokens
@@ -357,14 +361,17 @@ fn parse_interpolate<'input>(input: &mut Input<'input>) -> PResult<'input, Vec<T
         })
         .parse_next(input)?;
 
+    let right_trim = opt("-".map(TemplateToken::trim_whitespace)).parse_next(input)?;
     let right_delim = "}}".map(TemplateToken::right_delim).parse_next(input)?;
     let post_whitespace = opt(parse_whitespace).parse_next(input)?;
 
     let mut tokens = vec![];
     tokens.extend(prev_whitespace);
     tokens.push(left_delim);
+    tokens.extend(left_trim);
     tokens.extend(wants_output);
     tokens.extend(inside_tokens);
+    tokens.extend(right_trim);
     tokens.push(right_delim);
     tokens.extend(post_whitespace);
 
@@ -595,4 +602,29 @@ mod tests {
         )
         "#);
     }
+
+    #[test]
+    fn parse_trim_whitespace() {
+        let input = "\n\n{{-= hello -}} \n\n";
+        let output = parse(input.into());
+
+        insta::assert_debug_snapshot!(output, @r#"
+        Ok(
+            ParsedTemplate {
+                tokens: [
+                    [Whitespace]"\n\n" (0..2),
+                    [LeftDelim]"{{" (2..4),
+                    [TrimWhitespace]"-" (4..5),
+                    [WantsOutput]"=" (5..6),
+                    [Whitespace]" " (6..7),
+                    [Ident]"hello" (7..12),
+                    [Whitespace]" " (12..13),
+                    [TrimWhitespace]"-" (13..14),
+                    [RightDelim]"}}" (14..16),
+                    [Whitespace]" \n\n" (16..19),
+                ],
+            },
+        )
+        "#);
+    }
 }