Add support for unary operators (fixes #83)

2 files changed, 18 insertions, 1 deletions

diff --git a/askama_derive/src/generator.rs b/askama_derive/src/generator.rs
index b110a89..0050d35 100644
--- a/askama_derive/src/generator.rs
+++ b/askama_derive/src/generator.rs
@@ -620,6 +620,7 @@ impl<'a> Generator<'a> {
             Expr::Array(ref elements) => self.visit_array(elements, code),
             Expr::Attr(ref obj, name) => self.visit_attr(obj, name, code),
             Expr::Filter(name, ref args) => self.visit_filter(name, args, code),
+            Expr::Unary(op, ref inner) => self.visit_unary(op, inner, code),
             Expr::BinOp(op, ref left, ref right) => self.visit_binop(op, left, right, code),
             Expr::Group(ref inner) => self.visit_group(inner, code),
             Expr::MethodCall(ref obj, method, ref args) => {
@@ -766,6 +767,12 @@ impl<'a> Generator<'a> {
         DisplayWrap::Unwrapped
     }
 
+    fn visit_unary(&mut self, op: &str, inner: &Expr, code: &mut String) -> DisplayWrap {
+        code.push_str(op);
+        self.visit_expr(inner, code);
+        DisplayWrap::Unwrapped
+    }
+
     fn visit_binop(&mut self, op: &str, left: &Expr, right: &Expr, code: &mut String)
                    -> DisplayWrap {
         self.visit_expr(left, code);
diff --git a/askama_derive/src/parser.rs b/askama_derive/src/parser.rs
index f1e3c72..d15fc1a 100644
--- a/askama_derive/src/parser.rs
+++ b/askama_derive/src/parser.rs
@@ -13,6 +13,7 @@ pub enum Expr<'a> {
     Array(Vec<Expr<'a>>),
     Attr(Box<Expr<'a>>, &'a str),
     Filter(&'a str, Vec<Expr<'a>>),
+    Unary(&'a str, Box<Expr<'a>>),
     BinOp(&'a str, Box<Expr<'a>>, Box<Expr<'a>>),
     Group(Box<Expr<'a>>),
     MethodCall(Box<Expr<'a>>, &'a str, Vec<Expr<'a>>),
@@ -366,6 +367,15 @@ named!(expr_filtered<Expr>, do_parse!(
     })
 ));
 
+named!(expr_unary<Expr>, do_parse!(
+    op: opt!(alt!(tag_s!("!") | tag_s!("-"))) >>
+    expr: expr_filtered >>
+    (match op {
+        Some(op) => Expr::Unary(str::from_utf8(op).unwrap(), Box::new(expr)),
+        None => expr,
+    })
+));
+
 macro_rules! expr_prec_layer {
     ( $name:ident, $inner:ident, $( $op:expr ),* ) => {
         named!($name<Expr>, do_parse!(
@@ -381,7 +391,7 @@ macro_rules! expr_prec_layer {
     }
 }
 
-expr_prec_layer!(expr_muldivmod, expr_filtered, "*", "/", "%");
+expr_prec_layer!(expr_muldivmod, expr_unary, "*", "/", "%");
 expr_prec_layer!(expr_addsub, expr_muldivmod, "+", "-");
 expr_prec_layer!(expr_shifts, expr_addsub, ">>", "<<");
 expr_prec_layer!(expr_band, expr_shifts, "&");