Component ids

Pavex requires every component to have a unique component id.

Generation

Attributes will assign a default id to your component based on its name and item kind.

Item Kind	Naming Scheme	Example	Example ID
Function	<function name>	my_function()	MY_FUNCTION
Method	<type name>_<method name>	Span::new()	SPAN_NEW
Type	<type name>	struct MyType;	MY_TYPE

The generated id will always be converted to SCREAMING_SNAKE_CASE.

Using a custom id

You're not forced to use the default generated id. You can specify a custom one using the id argument, supported by all attributes:

use pavex::Response;
use pavex::methods;

pub struct AuthError {
    // [...]
}

#[methods]
impl AuthError {
    #[error_handler(id = "AUTH_ERROR_HANDLER")] // (1)!
    pub fn to_response(&self) -> Response {
        // [...]
    }
}

1. The default id would be AUTH_ERROR_TO_RESPONSE, but we're using the id argument to override it.

Generated constant

Every attribute will define a new constant next to the annotated component, named after the component's id. The generated constant can be used to refer to that component when interacting with a Blueprint.

use crate::auth_error::AUTH_ERROR_HANDLER;
use pavex::{Blueprint, blueprint::from};

pub fn blueprint() -> Blueprint {
    let mut bp = Blueprint::new();
    bp.error_handler(AUTH_ERROR_HANDLER);
    // [...]
}

The generated constants are strongly typed. Your project won't compile if you invoke the wrong Blueprint method—e.g. .route() for an error handler.

Uniqueness scope

The component id must be unique within the crate where the component is defined—e.g. two components with the same identifier from different crates won't cause an issue.