feat(panic): Add basic panic handler and installation function

Fixes: https://github.com/zkat/miette/issues/22

src/lib.rs

@@ -10,6 +10,7 @@ pub use eyreish::*;
 pub use handler::*;
 pub use handlers::*;
 pub use named_source::*;
+pub use panic::*;
 pub use protocol::*;
 
 mod chain;
@@ -19,5 +20,6 @@ mod eyreish;
 mod handler;
 mod handlers;
 mod named_source;
+mod panic;
 mod protocol;
 mod source_impls;

src/panic.rs

@@ -0,0 +1,30 @@
+use thiserror::Error;
+
+use crate::{self as miette, Context, Diagnostic, Result};
+
+/// Tells miette to render panics using its rendering engine.
+pub fn set_panic_hook() {
+    std::panic::set_hook(Box::new(|info| {
+        let mut message = "Something went wrong".to_string();
+        let payload = info.payload();
+        if let Some(msg) = payload.downcast_ref::<&str>() {
+            message = msg.to_string();
+        }
+        if let Some(msg) = payload.downcast_ref::<String>() {
+            message = msg.clone();
+        }
+        let mut report: Result<()> = Err(Panic(message).into());
+        if let Some(loc) = info.location() {
+            report = report
+                .with_context(|| format!("at {}:{}:{}", loc.file(), loc.line(), loc.column()));
+        }
+        if let Err(err) = report.with_context(|| "Main thread panicked.".to_string()) {
+            eprintln!("Error: {:?}", err);
+        }
+    }));
+}
+
+#[derive(Debug, Error, Diagnostic)]
+#[error("{0}")]
+#[diagnostic(help("set the `RUST_BACKTRACE=1` environment variable to display a backtrace."))]
+struct Panic(String);