Add `join` filter & tests for it

1 files changed, 25 insertions, 0 deletions

diff --git a/askama_shared/src/generator.rs b/askama_shared/src/generator.rs
index e5ffd08..836da34 100644
--- a/askama_shared/src/generator.rs
+++ b/askama_shared/src/generator.rs
@@ -238,10 +238,35 @@ impl<'a> Generator<'a> {
         self.write(")");
     }
 
+    fn _visit_join_filter(&mut self, args: &[Expr]) {
+        // this is a separate handler because we need to generate code like
+        // this to force auto-deref for first argument:
+        // `join((&&&&&&self.s).into_iter(), ", ")`
+        // otherwise, we were getting errors described in PR #39
+        self.write("::askama::filters::join((&");
+
+        for (i, arg) in args.iter().enumerate() {
+            if i > 0 {
+                self.write(", &");
+            }
+
+            self.visit_expr(arg);
+
+            if i == 0 {
+                self.write(").into_iter()");
+            }
+        }
+
+        self.write(")?");
+    }
+
     fn visit_filter(&mut self, name: &str, args: &[Expr]) {
         if name == "format" {
             self._visit_format_filter(args);
             return;
+        } else if name == "join" {
+            self._visit_join_filter(args);
+            return;
         }
 
         if BUILT_IN_FILTERS.contains(&name) {