The map_to_struct! Macro

The Problem

tauri-specta v1.0.2 doesn't support serde_json::Value - it can't generate TypeScript bindings for commands that use dynamic JSON values.

This broke our flexible state management pattern where we store settings as HashMap<String, Value> but need a strongly-typed struct for TypeScript bindings.

The Solution

A macro that converts between the two representations:

map_to_struct! {
    GroomingStateMap => GroomingRecord {
        fur_length_cm: i32,
        brush_type: String,
        shedding_score: u8,
        nail_trimmed: bool,
        favorite_spot: String,
    }
}

This generates a to_typed() method that extracts and converts each field automatically.

// Granular getter with specta support
#[tauri::command]
#[specta::specta]
pub fn get_frontend_state_value(key: String) -> Result<JsonValue, String> {
    with_state(|st8| {
        st8.front_end_state.get(&key)
            .cloned()
            .map(JsonValue)
            .ok_or_else(|| format!("Key not found: {}", key))
    })
}

// Get entire state as strongly typed struct
#[tauri::command]
#[specta::specta]
pub fn fetch_cached_state() -> Result<FrontEndSt8, String> {
    with_state(|st8| {
        st8.front_end_state.to_typed()
    })
}

Benefits

• Type-safe: Compiler verifies all conversions match the struct definition
• DRY: Field list appears once, conversion logic auto-generates
• Zero boilerplate: No manual extraction code for each field
• Works with tauri-specta: Commands accept/return the typed struct, which specta handles perfectly

Result: Flexible runtime storage with full TypeScript type safety in Tauri apps.