A panic hook for wasm32-unknown-unknown that logs panics with console.error

Rust and WebAssembly

Last update: Jan 3, 2023

Related tags

Command-line rust console wasm rust-wasm panic-hook

Overview

`console_error_panic_hook`

This crate lets you debug panics on wasm32-unknown-unknown by providing a panic hook that forwards panic messages to console.error.

When an error is reported with console.error, browser devtools and node.js will typically capture a stack trace and display it with the logged error message.

Without console_error_panic_hook you just get something like RuntimeError: Unreachable executed

Browser:

Node:

With this panic hook installed you will see the panic message

Browser:

Node:

Usage

There are two ways to install this panic hook.

First, you can set the hook yourself by calling std::panic::set_hook in some initialization function:

extern crate console_error_panic_hook;
use std::panic;

fn my_init_function() {
    panic::set_hook(Box::new(console_error_panic_hook::hook));

    // ...
}

Alternatively, use set_once on some common code path to ensure that set_hook is called, but only the one time. Under the hood, this uses std::sync::Once.

extern crate console_error_panic_hook;

struct MyBigThing;

impl MyBigThing {
    pub fn new() -> MyBigThing {
        console_error_panic_hook::set_once();

        MyBigThing
    }
}

Error.stackTraceLimit

Many browsers only capture the top 10 frames of a stack trace. In rust programs this is less likely to be enough. To see more frames, you can set the non-standard value Error.stackTraceLimit. For more information see the MDN Web Docs or v8 docs.

Comments

Doesn't work in Safari

What I see in Firefox:

What I see in Safari:

Edit:

wasm-bindgen generates this code:

const __wbg_error_29632ca09755cc79_target = console.error;

let cachedDecoder = new TextDecoder('utf-8');

// ...

export function __wbg_error_29632ca09755cc79(arg0, arg1) {
    let varg0 = getStringFromWasm(arg0, arg1);
    __wbg_error_29632ca09755cc79_target(varg0);
}

If this line:

__wbg_error_29632ca09755cc79_target(varg0);

is manually changed to this:

__wbg_error_29632ca09755cc79_target(varg0 + " ");

then it works. It seems that the string literal has to have a space in it, an empty string literal doesn't work.

opened by kzvi 7

Update readme to talk about Error.stackTraceLimit

Stack traces from rust, including the example screenshots in the existing documentation (!), are often so full of stack frames from the panic mechanism itself and other generic platform functions that there is not enough information to identify where the error was triggered in user code. Hopefully this documentation will save time for the next person who has this problem.

opened by itsybitesyspider 2
Expose panic formatting as function

Enso developers would like to implement a panic hook that writes to console.error, but also uses an application-specific API to write the panic info to the console running the program as an electron app. The latter is straightforward enough, but console_error_panic_hook's formatting addresses browser subtleties, and we'd prefer not to duplicate that.

This PR exposes panic formatting in the API, for use from custom panic hooks.

opened by kazcw 1
Error when used with `cargo web`
As soon as I start my app I get the following in the console and a broken app:

Uncaught (in promise) TypeError: Import #5 module="__wbindgen_placeholder__" error: module is not an object or function
opened by estk 1
Use the new feature flag for procedural macros

See https://github.com/rustwasm/wasm-bindgen/commit/ed05c7b9454905f15488714619950a55cd3c8d2d

Apparently the feature flag for proc macros was renamed to use_extern_macros.

opened by migerh 1
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dependencies

opened by dependabot-preview[bot] 0

Make FireFox Put the @URL Part on Its Own Column

On Firefox 72.0.2, noticed that the URL part of the stack trace isn't lined up like in the README. So manually added some periods to space things out.

Here's an example of what I'm seeing:

Stack:

init/imports.wbg.__wbg_new_59cb74e423758ede@http://localhost:1234/rust.js:303:23
console_error_panic_hook::Error::new::h21c6f8c021401ca7@http://localhost:1234/rust.wasm:wasm-function[1312]:0x7004a
console_error_panic_hook::hook_impl::h51d369253f11867c@http://localhost:1234/rust.wasm:wasm-function[240]:0x49b09
console_error_panic_hook::hook::h7240c976685d8fda@http://localhost:1234/rust.wasm:wasm-function[1407]:0x7179f
core::ops::function::Fn::call::hd089ec940b4dcbbd@http://localhost:1234/rust.wasm:wasm-function[1318]:0x701f6
std::panicking::rust_panic_with_hook::h4e529e530989255b@http://localhost:1234/rust.wasm:wasm-function[372]:0x543e3
std::panicking::begin_panic::h1f5bf870a56b785e@http://localhost:1234/rust.wasm:wasm-function[512]:0x5b698
BugCraft::game::Game::update::h168b1700ce7fdc84@http://localhost:1234/rust.wasm:wasm-function[16]:0xcd4d
BugCraft::update::hc4c0739190f6c8fa@http://localhost:1234/rust.wasm:wasm-function[1315]:0x70131
update@http://localhost:1234/rust.wasm:wasm-function[1103]:0x6c350
_on_update@http://localhost:1234/typescript.js:341:28

Testing

Verified cargo test still passes, that this doesn't affect Chrome, and that Firefox now looks like:

Stack:

init/imports.wbg.__wbg_new_59cb74e423758ede ............. @http://localhost:1234/rust.js:303:23
console_error_panic_hook::Error::new::hbe0bf58356f924b2 . @http://localhost:1234/rust.wasm:wasm-function[1405]:0x781b7
console_error_panic_hook::hook_impl::ha653d0da3dbebdd3 .. @http://localhost:1234/rust.wasm:wasm-function[38]:0x24828
console_error_panic_hook::hook::h4e971616aff3a927 ....... @http://localhost:1234/rust.wasm:wasm-function[1510]:0x79b76
core::ops::function::Fn::call::h8f08f944b67fcc08 ........ @http://localhost:1234/rust.wasm:wasm-function[1411]:0x78363
std::panicking::rust_panic_with_hook::h4e529e530989255b . @http://localhost:1234/rust.wasm:wasm-function[407]:0x5a67b
std::panicking::begin_panic::h1f5bf870a56b785e .......... @http://localhost:1234/rust.wasm:wasm-function[561]:0x624d2
BugCraft::game::Game::update::h168b1700ce7fdc84 ......... @http://localhost:1234/rust.wasm:wasm-function[16]:0xcdc3
BugCraft::update::hc4c0739190f6c8fa ..................... @http://localhost:1234/rust.wasm:wasm-function[1408]:0x7829e
update .................................................. @http://localhost:1234/rust.wasm:wasm-function[1188]:0x74269
_on_update .............................................. @http://localhost:1234/typescript.js:341:28

opened by aaron-human 0

Add example error message and backtrace from node

I wasn't sure where you wanted me to put the error messages, so I put them in .txt files.

For the purposes of reproduction, I generated the error messages from here: https://github.com/kylejlin/console-error-panic-hook-test

opened by kylejlin 0
Expose a function to stringify a PanicInfo struct

This allows users who want to display the error message generated by console_error_panic_hook outside of the console to do it without having to reimplement javascript-based stack walking themselves.

Hey! I'm in the process of trying to be nicer to users upon panic, displaying an error page on my yew app instead of just crashing and dumping logs to the console (source). However, I'd rather avoid reimplementing the stack walking that console_error_panic_hook implemented in order to tell the user what they should copy-paste to the issue tracker.

So I thought of just exposing it from console_error_panic_hook, though it may be slightly outside of the expected API surface for it.

WDYT?

opened by Ekleog 0
Expose panic formatting in API

Hi, I'm working on an Electron application, Enso. Enso needs to do multiple things in our panic hook: We have an application-specific API to submit the backtrace to, but we'd also like to display it with console.error. We want to minimize duplication of the functionality defined in console_error_panic_hook--especially the backtrace formatting, since it addresses browser subtleties.

This proposed change introduces a lower level function to the API, exposing the panic formatting functionality for use from another hook.

(Also, it increments the release version in Cargo.toml to match the currently-released version.)

opened by kazcw 1
Source commit and tag for 0.1.7 missing
Describe the Bug

Crates.io lists 0.1.7 as the latest release, but there's no tag in the repo for that version.

The metadata points to commit f998b08b76655c16b948fc329c26ba563e9b3384 which also doesn't seem to be published. The only source difference from the current head (4dc30a5448ed3ffcfb961b1ad54d000cca881b84) seems to be the version bump.

Steps to Reproduce

Go to https://crates.io/crates/console_error_panic_hook/versions

Obvserve published versions

git clone https://github.com/rustwasm/console_error_panic_hook

cd console_error_panic_hook

git show 0.1.7

See error unknown revision or path not in the working tree.

If applicable, add a link to a test case (as a zip file or link to a repository we can clone).

Expected Behavior

It's convenient for auditing changes if the source of each release is tagged in the official repository.

Could you please push the release commit and tag?
bug
opened by rillian 1
customer panicinfo info
in release we do not want to show full compilation file path from panic info

because it reveals interanals

can we disable it, may be via some feature gate?

enhancement
opened by dzmitry-lahoda 0
Update cfg-if requirement from 0.1.6 to 1.0.0
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Updates the requirements on cfg-if to permit the latest version.

Commits

e60fa1e Bump to 1.0.0

7daa598 Prohibit multiple predicates (#37)

f71bf60 Another attempt at gh-pages

f779d28 Change push username for gh-pages

4484a6f Bump to 0.1.10

a625fbe Add a test for the body of an impl

33a8869 Merge pull request #28 from Lokathor/token-trees

571a28d remove the __apply internal macro

75e817f adjust the test

3e9d487 notes fix

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dependencies
opened by dependabot-preview[bot] 2