salsa 0.26.1

#[cfg(test)]
use std::sync::{Arc, Mutex};

// ANCHOR: db_struct
#[salsa::db]
#[derive(Clone)]
#[cfg_attr(not(test), derive(Default))]
pub struct CalcDatabaseImpl {
    storage: salsa::Storage<Self>,

    // The logs are only used for testing and demonstrating reuse:
    #[cfg(test)]
    logs: Arc<Mutex<Option<Vec<String>>>>,
}

#[cfg(test)]
impl Default for CalcDatabaseImpl {
    fn default() -> Self {
        let logs = <Arc<Mutex<Option<Vec<String>>>>>::default();
        Self {
            storage: salsa::Storage::new(Some(Box::new({
                let logs = logs.clone();
                move |event| {
                    eprintln!("Event: {event:?}");
                    // Log interesting events, if logging is enabled
                    if let Some(logs) = &mut *logs.lock().unwrap() {
                        // only log interesting events
                        if let salsa::EventKind::WillExecute { .. } = event.kind {
                            logs.push(format!("Event: {event:?}"));
                        }
                    }
                }
            }))),
            logs,
        }
    }
}
// ANCHOR_END: db_struct

impl CalcDatabaseImpl {
    /// Enable logging of each salsa event.
    #[cfg(test)]
    pub fn enable_logging(&self) {
        let mut logs = self.logs.lock().unwrap();
        if logs.is_none() {
            *logs = Some(vec![]);
        }
    }

    #[cfg(test)]
    #[allow(unused)]
    pub fn take_logs(&self) -> Vec<String> {
        let mut logs = self.logs.lock().unwrap();
        if let Some(logs) = &mut *logs {
            std::mem::take(logs)
        } else {
            vec![]
        }
    }
}

// ANCHOR: db_impl
#[salsa::db]
impl salsa::Database for CalcDatabaseImpl {}
// ANCHOR_END: db_impl