How to deserialize nested JSON

Define a struct with #[derive(serde::Deserialize)] and use #[serde(rename_all = "kebab-case")] to map nested JSON keys to Rust fields. The serde crate automatically handles the nesting hierarchy based on your struct definition.

#[derive(serde::Deserialize)]
#[serde(rename_all = "kebab-case")]
struct Config {
    output_mode: Mode,
}

let config: Config = serde_json::from_str(json_str)?;

For deeply nested paths like preprocessor.test-preprocessor, access the specific section from the parent context before deserializing:

let config: Config = ctx
    .config
    .get(&format!("preprocessor.{preprocessor_name}"))?
    .ok_or_else(|| Error::NoConfig(preprocessor_name.into()))?;

Deserializing nested JSON means converting a structured text format into a specific Rust data structure. You define a Rust struct that mirrors the JSON shape, and the serde library automatically fills the struct fields with the correct data from the text. It's like filling out a form where the JSON provides the answers and your struct defines the boxes to put them in.