Merge pull request rustwasm#10 from rustwasm/fml

Include stacks in logged messages; fix misbehaving browser devtools

Author: alexcrichton

src/lib.rs

@@ -79,10 +79,42 @@ cfg_if! {
  extern {
  #[wasm_bindgen(js_namespace = console)]
  fn error(msg: String);
+
+ type Error;
+
+ #[wasm_bindgen(constructor)]
+ fn new() -> Error;
+
+ #[wasm_bindgen(structural, method, getter)]
+ fn stack(error: &Error) -> String;
  }
 
  fn hook_impl(info: &panic::PanicInfo) {
- error(info.to_string());
+ let mut msg = info.to_string();
+
+ // Add the error stack to our message.
+ //
+ // This ensures that even if the `console` implementation doesn't
+ // include stacks for `console.error`, the stack is still available
+ // for the user. Additionally, Firefox's console tries to clean up
+ // stack traces, and ruins Rust symbols in the process
+ // (https://bugzilla.mozilla.org/show_bug.cgi?id=1519569) but since
+ // it only touches the logged message's associated stack, and not
+ // the message's contents, by including the stack in the message
+ // contents we make sure it is available to the user.
+ msg.push_str("\n\nStack:\n\n");
+ let e = Error::new();
+ let stack = e.stack();
+ msg.push_str(&stack);
+
+ // Safari's devtools, on the other hand, _do_ mess with logged
+ // messages' contents, so we attempt to break their heuristics for
+ // doing that by appending some whitespace.
+ // https://github.com/rustwasm/console_error_panic_hook/issues/7
+ msg.push_str("\n\n");
+
+ // Finally, log the panic with `console.error`!
+ error(msg);
  }
  } else {
  use std::io::{self, Write};