Check for None-delimited group in attribute value

serde_derive/Cargo.toml

@@ -24,7 +24,7 @@ proc-macro = true
 [dependencies]
 proc-macro2 = "1.0"
 quote = "1.0"
-syn = "2.0"
+syn = "2.0.3"
 
 [dev-dependencies]
 serde = { version = "1.0", path = "../serde" }

serde_derive/src/internals/attr.rs

@@ -1381,21 +1381,26 @@ fn get_lit_str2(
     meta_item_name: Symbol,
     meta: &ParseNestedMeta,
 ) -> syn::Result<Option<syn::LitStr>> {
-    match meta.value()?.parse()? {
+    let expr: syn::Expr = meta.value()?.parse()?;
-        syn::Expr::Lit(syn::ExprLit {
+    let mut value = &expr;
-            lit: syn::Lit::Str(lit),
+    while let syn::Expr::Group(e) = value {
-            ..
+        value = &e.expr;
-        }) => Ok(Some(lit)),
+    }
-        expr => {
+    if let syn::Expr::Lit(syn::ExprLit {
-            cx.error_spanned_by(
+        lit: syn::Lit::Str(lit),
-                expr,
+        ..
-                format!(
+    }) = value
-                    "expected serde {} attribute to be a string: `{} = \"...\"`",
+    {
-                    attr_name, meta_item_name
+        Ok(Some(lit.clone()))
-                ),
+    } else {
-            );
+        cx.error_spanned_by(
-            Ok(None)
+            expr,
-        }
+            format!(
+                "expected serde {} attribute to be a string: `{} = \"...\"`",
+                attr_name, meta_item_name
+            ),
+        );
+        Ok(None)
     }
 }