Improved template loop generation

askama_shared/src/generator.rs

@@ -667,8 +667,26 @@ impl<'a, S: std::hash::BuildHasher> Generator<'a, S> {
                 ", _loop_item) in ::askama::helpers::TemplateLoop::new({}) {{",
                 expr_code
             )),
+            Expr::Array(..) => buf.writeln(&format!(
+                ", _loop_item) in ::askama::helpers::TemplateLoop::new({}.iter()) {{",
+                expr_code
+            )),
+            // If `iter` is a call then we assume it's something that returns
+            // an iterator. If not then the user can explicitly add the needed
+            // call without issues.
+            Expr::MethodCall(..) | Expr::PathCall(..) | Expr::Index(..) => buf.writeln(&format!(
+                ", _loop_item) in ::askama::helpers::TemplateLoop::new(({}).into_iter()) {{",
+                expr_code
+            )),
+            // If accessing `self` then it most likely needs to be
+            // borrowed, to prevent an attempt of moving.
+            _ if expr_code.starts_with("self.") => buf.writeln(&format!(
+                ", _loop_item) in ::askama::helpers::TemplateLoop::new(((&{}).into_iter())) {{",
+                expr_code
+            )),
+            // Otherwise, we borrow `iter` assuming that it implements `IntoIterator`.
             _ => buf.writeln(&format!(
-                ", _loop_item) in ::askama::helpers::TemplateLoop::new((&{}).into_iter()) {{",
+                ", _loop_item) in ::askama::helpers::TemplateLoop::new(({}).into_iter()) {{",
                 expr_code
             )),
         }?;

testing/tests/loops.rs

@@ -67,3 +67,39 @@ fn test_for_range() {
         "foo (first)\nfoo (last)\nbar\nbar\nfoo\nbar\nbar\n"
     );
 }
+
+#[derive(Template)]
+#[template(source = "{% for i in [1, 2, 3] %}{{ i }}{% endfor %}", ext = "txt")]
+struct ForArrayTemplate {}
+
+#[test]
+fn test_for_array() {
+    let t = ForArrayTemplate {};
+    assert_eq!(t.render().unwrap(), "123");
+}
+
+#[derive(Template)]
+#[template(
+    source = "{% for i in [1, 2, 3].iter() %}{{ i }}{% endfor %}",
+    ext = "txt"
+)]
+struct ForMethodCallTemplate {}
+
+#[test]
+fn test_for_method_call() {
+    let t = ForMethodCallTemplate {};
+    assert_eq!(t.render().unwrap(), "123");
+}
+
+#[derive(Template)]
+#[template(
+    source = "{% for i in [1, 2, 3, 4, 5][3..] %}{{ i }}{% endfor %}",
+    ext = "txt"
+)]
+struct ForIndexTemplate {}
+
+#[test]
+fn test_for_index() {
+    let t = ForIndexTemplate {};
+    assert_eq!(t.render().unwrap(), "45");
+}