Using std::result::Result in request/response structures

[Slonegg]

I have a structure that contains Result. Simplified example:

#[derive(Serialize, Deserialize, ToSchema)]
pub struct CommandResult {
    result: Result<CommandOutput, String>,
}

The endpoint works fine. However, I'm struggling to get the documentation rendered with Utoipa.

Apparently the problem is with the schema for the Result type. Adding Result<CommandOutput, String> to schemas results in the following error:

 the trait `ToSchema<'_>` is not implemented for `std::result::Result<CommandOutput, std::string::String>`

Or is the idea to implement ToSchema for the aforementioned type somehow?

[juhaku]

Hey,

This is same situation as with serde in order to support external types that are not declared with Serialize or Deserialize. To this purpose serde has the serialize_with attribute. For what comes to utoipa there are few ways around it depending the needs of user in general. You might want to follow links here #656 and #507 (comment).

But in nutshell you need to manually create the schema for the the result type which should mimic the what the Result should look like in generated OpenAPI. Most likely it should be something like oneOf selection.

Hope this helps.

[Slonegg]

Thank you. Adding the following struct has resolved the issue:

#[derive(ToSchema)]
#[schema(as = Result<CommandOutput, String>)]
pub enum CommandResultSchema {
    Ok(CommandOutput),
    Err(String),
}