templater: parse "\t" and "\r" as escape sequence

src/template.pest

@@ -19,7 +19,7 @@
 
 whitespace = _{ " " | "\t" | "\n" }
 
-escape = @{ "\\" ~ ("n" | "\"" | "\\") }
+escape = @{ "\\" ~ ("t" | "r" | "n" | "\"" | "\\") }
 literal_char = @{ !("\"" | "\\") ~ ANY }
 raw_literal = @{ literal_char+ }
 literal = { "\"" ~ (raw_literal | escape)* ~ "\"" }

src/template_parser.rs

@@ -258,6 +258,8 @@ fn parse_string_literal(pair: Pair<Rule>) -> String {
             Rule::escape => match part.as_str().as_bytes()[1] as char {
                 '"' => result.push('"'),
                 '\\' => result.push('\\'),
+                't' => result.push('\t'),
+                'r' => result.push('\r'),
                 'n' => result.push('\n'),
                 char => panic!("invalid escape: \\{char:?}"),
             },
@@ -1261,6 +1263,21 @@ mod tests {
         assert!(parse_template(r#" label("",,"") "#).is_err());
     }
 
+    #[test]
+    fn test_string_literal() {
+        // "\<char>" escapes
+        assert_eq!(
+            parse_into_kind(r#" "\t\r\n\"\\" "#),
+            Ok(ExpressionKind::String("\t\r\n\"\\".to_owned())),
+        );
+
+        // Invalid "\<char>" escape
+        assert_eq!(
+            parse_into_kind(r#" "\y" "#),
+            Err(TemplateParseErrorKind::SyntaxError),
+        );
+    }
+
     #[test]
     fn test_integer_literal() {
         assert_eq!(parse_into_kind("0"), Ok(ExpressionKind::Integer(0)));