Implement Display for all Templates

askama_derive/src/generator.rs

@@ -47,6 +47,7 @@ pub fn generate(ast: &syn::DeriveInput, path: &str, mut nodes: Vec<Node>) -> Str
     } else {
         gen.impl_template(ast, &content);
     }
+    gen.impl_display(ast);
     gen.result()
 }
 
@@ -490,6 +491,15 @@ impl<'a> Generator<'a> {
         self.writeln("}");
     }
 
+    // Implement `Display` for the given context struct.
+    fn impl_display(&mut self, ast: &syn::DeriveInput) {
+        self.write_header(ast, "::std::fmt::Display");
+        self.writeln("fn fmt(&self, f: &mut ::std::fmt::Formatter) -> Result<(), ::std::fmt::Error> {");
+        self.writeln("self.render_into(f)");
+        self.writeln("}");
+        self.writeln("}");
+    }
+
     // Implement `Deref<Parent>` for an inheriting context struct.
     fn deref_to_parent(&mut self, ast: &syn::DeriveInput, parent_type: &syn::Ty) {
         self.write_header(ast, "::std::ops::Deref");

testing/tests/simple.rs

@@ -154,3 +154,16 @@ fn test_json() {
     let t = JsonTemplate { foo: "a", bar: "b" };
     assert_eq!(t.render().unwrap(), "{\"foo\": \"a\", \"bar\": \"b\"}");
 }
+
+
+#[derive(Template)]
+#[template(path = "composition.html")]
+struct CompositionTemplate {
+    foo: IfTemplate,
+}
+
+#[test]
+fn test_composition() {
+    let t = CompositionTemplate { foo: IfTemplate { cond: true } };
+    assert_eq!(t.render().unwrap(), "composed: true");
+}