72 lines
2.4 KiB
Markdown
72 lines
2.4 KiB
Markdown
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## `console_error_panic_hook`
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[![](https://docs.rs/console_error_panic_hook/badge.svg)](https://docs.rs/console_error_panic_hook/)
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[![](https://img.shields.io/crates/v/console_error_panic_hook.svg)](https://crates.io/crates/console_error_panic_hook)
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[![](https://img.shields.io/crates/d/console_error_panic_hook.png)](https://crates.io/crates/console_error_panic_hook)
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[![Build Status](https://travis-ci.org/rustwasm/console_error_panic_hook.svg?branch=master)](https://travis-ci.org/rustwasm/console_error_panic_hook)
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This crate lets you debug panics on `wasm32-unknown-unknown` by providing a
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panic hook that forwards panic messages to
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[`console.error`](https://developer.mozilla.org/en-US/docs/Web/API/Console/error).
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When an error is reported with `console.error`, browser devtools and node.js
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will typically capture a stack trace and display it with the logged error
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message.
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Without `console_error_panic_hook` you just get something like *RuntimeError: Unreachable executed*
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Browser:
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![Console without panic hook](without_panic_hook.png)
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Node:
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![Node console without panic hook](without_panic_hook_node.png)
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With this panic hook installed you will see the panic message
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Browser:
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![Console with panic hook set up](with_panic_hook.png)
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Node:
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![Node console with panic hook set up](with_panic_hook_node.png)
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### Usage
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There are two ways to install this panic hook.
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First, you can set the hook yourself by calling `std::panic::set_hook` in
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some initialization function:
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```rust
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extern crate console_error_panic_hook;
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use std::panic;
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fn my_init_function() {
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panic::set_hook(Box::new(console_error_panic_hook::hook));
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// ...
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}
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```
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Alternatively, use `set_once` on some common code path to ensure that
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`set_hook` is called, but only the one time. Under the hood, this uses
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`std::sync::Once`.
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```rust
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extern crate console_error_panic_hook;
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struct MyBigThing;
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impl MyBigThing {
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pub fn new() -> MyBigThing {
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console_error_panic_hook::set_once();
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MyBigThing
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}
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}
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```
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### Error.stackTraceLimit
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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](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Microsoft_Extensions/Error.stackTraceLimit) or [v8 docs](https://v8.dev/docs/stack-trace-api).
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