Merge pull request #43 from GuillaumeGomez/move-in-let-statement

Prevent jinja `let` to move variables

rinja_derive/src/generator.rs

@@ -921,7 +921,12 @@ impl<'a> Generator<'a> {
         }
 
         self.visit_target(buf, true, true, &l.var);
-        buf.writeln(format_args!(" = {};", &expr_buf.buf));
+        let (before, after) = if !is_copyable(val) {
+            ("&(", ")")
+        } else {
+            ("", "")
+        };
+        buf.writeln(format_args!(" = {before}{}{after};", &expr_buf.buf));
         Ok(())
     }
 
@@ -2121,7 +2126,7 @@ fn is_copyable_within_op(expr: &Expr<'_>, within_op: bool) -> bool {
         // The result of a call likely doesn't need to be borrowed,
         // as in that case the call is more likely to return a
         // reference in the first place then.
-        Expr::Call(..) | Expr::Path(..) => true,
+        Expr::Call(..) | Expr::Path(..) | Expr::Filter(..) => true,
         // If the `expr` is within a `Unary` or `BinOp` then
         // an assumption can be made that the operand is copy.
         // If not, then the value is moved and adding `.clone()`

testing/tests/ref_deref.rs

@@ -39,7 +39,7 @@ fn test_ref_deref() {
 #[derive(Template)]
 #[template(
     source = r#"
-{%- let x = *title -%}
+{%- let x = **title -%}
 {%- if x == "another" -%}
 another2
 {%- else -%}

testing/tests/vars.rs

@@ -131,3 +131,23 @@ fn test_decl_assign_range() {
     let t = DeclAssignRange;
     assert_eq!(t.render().unwrap(), "1");
 }
+
+#[derive(Template)]
+#[template(
+    source = "
+{%- set t = title -%}
+{{t}}/{{title -}}
+",
+    ext = "txt"
+)]
+struct DoNotMoveFields {
+    title: String,
+}
+
+#[test]
+fn test_not_moving_fields_in_var() {
+    let x = DoNotMoveFields {
+        title: "a".to_string(),
+    };
+    assert_eq!(x.render().unwrap(), "a/a");
+}