Consider adding axum::json!

[carllerche]

Feature Request

Consider adding an axum::json! macro that matches the serde_json macro syntax and avoids the stutter:

async fn hello_world() -> impl IntoResponse {
    axum::json!({ "hello": "world" })
}

Motivation

Returning JSON is common. This would avoid adding an extra dependency in the end user's Cargo.toml and avoid some stutter (Json(json!(...))) without exposing the serde_json dependency.

[SabrinaJewson]

Given that this function returns impl IntoResponse anyway, might it be worth using an approach like typed-json to avoid the heap allocation?

[jplatte]

That's exactly the sort of thing I was planning to write myself! Really nice that it already exists. I think that crate can be used directly by wrapping the generated type in axum::Json (and documenting that people are free to write either -> Json<impl Serialize> or -> impl IntoResponse). Would you be interested in making a PR for it?

edit: Actually maybe that crate also supports borrowing as part of the json!() expression? If yes, we can't wrap the result in Json (but we can use [something like] ErasedJson from axum-extra, which would either have to be moved into axum, or be part of the macro expansion).