//! A micro-crate to enhance panic messages with context info. //! //! FIXME: upstream to ? use std::{cell::RefCell, panic, sync::Once}; pub fn enter(context: String) -> PanicContext { static ONCE: Once = Once::new(); ONCE.call_once(PanicContext::init); with_ctx(|ctx| ctx.push(context)); PanicContext { _priv: () } } #[must_use] pub struct PanicContext { _priv: (), } impl PanicContext { fn init() { let default_hook = panic::take_hook(); let hook = move |panic_info: &panic::PanicInfo<'_>| { with_ctx(|ctx| { if !ctx.is_empty() { eprintln!("Panic context:"); for frame in ctx.iter() { eprintln!("> {}\n", frame); } } default_hook(panic_info); }); }; panic::set_hook(Box::new(hook)); } } impl Drop for PanicContext { fn drop(&mut self) { with_ctx(|ctx| assert!(ctx.pop().is_some())); } } fn with_ctx(f: impl FnOnce(&mut Vec)) { thread_local! { static CTX: RefCell> = RefCell::new(Vec::new()); } CTX.with(|ctx| f(&mut *ctx.borrow_mut())); }