fix test

libs/flags/json_flag.go

@@ -60,17 +60,17 @@ func (j *JsonFlag) Unmarshal(v any) diag.Diagnostics {
 	// It will serialize all set data with the correct types.
 	data, err := json.Marshal(nv.AsAny())
 	if err != nil {
-		return diag.FromErr(err)
+		return diags.Extend(diag.FromErr(err))
 	}
 
 	// Finally unmarshal the normalized data to the output.
 	// It will fill in the ForceSendFields field if the struct contains it.
 	err = marshal.Unmarshal(data, v)
 	if err != nil {
-		return diag.FromErr(err)
+		return diags.Extend(diag.FromErr(err))
 	}
 
-	return nil
+	return diags
 }
 
 func (j *JsonFlag) Type() string {