Initial implementation of the newline_to_br filter

Author: djwf

src/filters.rs

@@ -403,6 +403,15 @@ pub fn modulo(input: &Value, args: &[Value]) -> FilterResult {
     }
 }
 
+/// Replaces every newline (`\n`) with an HTML line break (`<br>`).
+pub fn newline_to_br(input: &Value, args: &[Value]) -> FilterResult {
+    try!(check_args_len(args, 0));
+    match *input {
+        Str(ref x) => Ok(Str(x.replace("\n", "<br />"))),
+        _ => Err(InvalidType("String expected".to_owned())),
+    }
+}
+
 /// Returns the number of already escaped characters.
 fn nr_escaped(text: &str) -> usize {
     for prefix in &["lt;", "gt;", "#39;", "quot;", "amp;"] {
@@ -875,6 +884,31 @@ mod tests {
         assert_eq!(unit!(modulo, Num(183.357), &[Num(12_f32)]), Num(3.3569946));
     }
 
+    #[test]
+    fn unit_newline_to_br() {
+        let input = &tos!("a\nb");
+        let args = &[];
+        let desired_result = tos!("a<br />b");
+        assert_eq!(unit!(newline_to_br, input, args), desired_result);
+    }
+
+    #[test]
+    fn unit_newline_to_br_one_argument() {
+        let input = &tos!("a\nb");
+        let args = &[Num(0f32)];
+        let desired_result = FilterError::InvalidArgumentCount("expected 0, 1 given".to_owned());
+        assert_eq!(failed!(newline_to_br, input, args), desired_result);
+    }
+
+    #[test]
+    fn unit_newline_to_br_hello_world() {
+        /// First example from https://shopify.github.io/liquid/filters/newline_to_br/
+        let input = &tos!("\nHello\nWorld\n");
+        let args = &[];
+        let desired_result = tos!("<br />Hello<br />World<br />");
+        assert_eq!(unit!(newline_to_br, input, args), desired_result);
+    }
+
     #[test]
     fn unit_escape() {
         assert_eq!(unit!(escape, tos!("Have you read 'James & the Giant Peach'?")),

src/template.rs

@@ -3,7 +3,7 @@ use context::Context;
 use filters::{size, upcase, downcase, capitalize, minus, plus, times, divided_by, ceil, floor,
               round, prepend, append, first, last, pluralize, replace_first, replace, date, sort,
               slice, modulo, escape, escape_once, remove_first, remove, reverse, strip_html,
-              truncatewords};
+              truncatewords, newline_to_br};
 use filters::split;
 use filters::join;
 use error::Result;
@@ -29,6 +29,7 @@ impl Renderable for Template {
         context.maybe_add_filter("last", Box::new(last));
         context.maybe_add_filter("minus", Box::new(minus));
         context.maybe_add_filter("modulo", Box::new(modulo));
+        context.maybe_add_filter("newline_to_br", Box::new(newline_to_br));
         context.maybe_add_filter("pluralize", Box::new(pluralize));
         context.maybe_add_filter("plus", Box::new(plus));
         context.maybe_add_filter("prepend", Box::new(prepend));