JSON Post Request Payload Validation?

[guzman109]

In a post request, there is a payload that should be validated with the following schema,

struct CreateAccountSchema {
  std::string Name;
  std::string PlatformId;
};

I try to validate it with the following snippet I got from the docs.

Router.post("/accounts", [Database](const glz::request &Request, glz::response &Response) {
    CreateAccountSchema AccountData;
    if (auto JsonError = glz::read_json(AccountData, Request.body)) {
      Response.status(static_cast<int>(BadRequest))
          .json({{"error", "Invalid JSON"}});
      return;
    }

But the following payload still went through,

{
  "Name": "guzman109",
}

Any advice on how I can enforce all fields are correct? Luckily I handled it before it got committed to the database but I would like to see that it was an invalid payload.

I come from writing backends in FastAPI and validating with Pydantic. My thought was that glaze would be similar, then again I'm most likely using it incorrectly.

[stephenberry]

By default, glz::read_json does not error on missing keys — any fields absent from the JSON are left at their default-constructed values. This is why your payload with only "Name" passes without error.

To enforce that all fields are present, use glz::read with the error_on_missing_keys option:

CreateAccountSchema AccountData;
constexpr my_opts = glz::opts{.error_on_missing_keys = true};
if (auto JsonError = glz::read<my_opts>(AccountData, Request.body)) {
   Response.status(static_cast<int>(BadRequest))
       .json({{"error", "Invalid JSON"}});
   return;
}

This will return glz::error_code::missing_key if any non-nullable field is missing from the input JSON.

A few additional notes:

• Nullable types like std::optional<T> and pointers are automatically treated as optional, even with this flag enabled. So if you want a field to be truly optional, declare it as std::optional<std::string>.
• If you need per-field control over which keys are required, you can specialize glz::meta<T>::requires_key():

template <>
struct glz::meta<CreateAccountSchema> {
   static constexpr bool requires_key(std::string_view key, bool is_nullable) {
      // Custom logic per field
      return !is_nullable;
   }
};

See docs/field-validation.md and docs/options.md for more details.