Add test showing decorator behaviour in deep partials

tests/decorator.rs

@@ -0,0 +1,38 @@
+use handlebars::*;
+use serde_derive::Serialize;
+use serde_json::json;
+
+fn insert_key(
+    _: &handlebars::Decorator,
+    _: &Handlebars,
+    ctx: &handlebars::Context,
+    rc: &mut handlebars::RenderContext,
+) -> Result<(), handlebars::RenderError> {
+    if let serde_json::Value::Object(m) = ctx.data() {
+        let mut new_ctx_data = dbg!(m.clone());
+        new_ctx_data.insert(
+            "key".to_string(),
+            serde_json::to_value(vec!["value"]).unwrap(),
+        );
+        rc.set_context(handlebars::Context::wraps(dbg!(new_ctx_data))?);
+        Ok(())
+    } else {
+        Err(handlebars::RenderError::new(
+            "Cannot extend non-object data",
+        ))
+    }
+}
+
+#[test]
+fn test_deep_decorator() {
+    let mut r = Handlebars::new();
+    r.register_decorator("d", Box::new(insert_key));
+    let root = json!({"child": {"inner_child": {"list": ["list"]}}});
+
+    // define two helpers; one that calls the other, and then the inner one adds the new field to the context
+    let template = r#"{{#*inline "child"}}{{> innerchild inner_child}}{{/inline}}{{#*inline "innerchild"}}{{*d}}{{list}}{{key}}{{/inline}}{{> child child}}"#;
+    assert_eq!(
+        "[list, ][value, ]",
+        &r.render_template(template, &root).unwrap()
+    );
+}