Parse conditional access

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

src/parser/mod.rs

@@ -2,6 +2,7 @@ use thiserror::Error;
 use winnow::Parser;
 use winnow::RecoverableParser;
 use winnow::combinator::Infix::Left;
+use winnow::combinator::Postfix;
 use winnow::combinator::alt;
 use winnow::combinator::cut_err;
 use winnow::combinator::delimited;
@@ -249,6 +250,7 @@ pub enum TemplateAstExpr<'input> {
         value_expression: Box<TemplateAstExpr<'input>>,
     },
     ForElse,
+    ConditionalAccess(TemplateToken),
     VariableAccess(TemplateToken),
     IfConditional {
         expression: Box<TemplateAstExpr<'input>>,
@@ -709,6 +711,16 @@ fn parse_expression<'input>(
                 Left Lesser => 15,
                 Left LesserOrEqual => 15,
             ]
+        }).postfix(dispatch! { surrounded(ws, parse_operator);
+            TokenOperator::QuestionMark => Postfix(22, |input, rhs| {
+                match rhs {
+                    TemplateAstExpr::VariableAccess(access) => Ok(TemplateAstExpr::ConditionalAccess(access)),
+                    _ => Err(AstError::from_input(input)),
+                }
+
+
+            }),
+            _ => fail
         }),
     )
     .parse_next(input)
@@ -1048,4 +1060,15 @@ mod tests {
 
         insta::assert_debug_snapshot!(ast);
     }
+
+    #[test]
+    fn check_conditional_access() {
+        let input = "{{= foo? }}";
+
+        let parsed = crate::lexer::parse(input.into()).unwrap();
+
+        let ast = panic_pretty(input, parse(parsed.tokens()));
+
+        insta::assert_debug_snapshot!(ast);
+    }
 }