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#![deny(missing_docs)]
#![doc(html_root_url = "https://docs.rs/console_log/0.1.2")]
//! A logger that logs to the browser's console.
//!
//! # Example
//!
//! ```rust,no_run
//! use log::Level;
//! use log::info;
//! fn main() {
//! console_log::init_with_level(Level::Debug);
//!
//! info!("It works!");
//!
//! // ...
//! }
//! ```
//!
//! # Log Levels
//!
//! Rust's log levels map to the browser's console log in the following way.
//!
//! | Rust | Web Console |
//! |------------|-------------------|
//! | `trace!()` | `console.debug()` |
//! | `debug!()` | `console.log()` |
//! | `info!()` | `console.info()` |
//! | `warn!()` | `console.warn()` |
//! | `error!()` | `console.error()` |
//!
//! # Getting Fancy
//!
//! The feature set provided by this crate is intentionally very basic. If you need more flexible
//! formatting of log messages (timestamps, file and line info, etc.) this crate can be used with
//! the [`fern`] logger via the [`console_log::log`] function.
//!
//! # Code Size
//!
//! [Twiggy] reports this library adding about 180Kb to the size of a minimal wasm binary in a
//! debug build. If you want to avoid this, mark the library as optional and conditionally
//! initialize it in your code for non-release builds.
//!
//! `Cargo.toml`
//! ```toml
//! [dependencies]
//! cfg_if = "0.1"
//! log = "0.4"
//! console_log = { version = "0.1", optional = true }
//!
//! [features]
//! default = ["console_log"]
//! ```
//!
//! `lib.rs`
//! ```rust,ignore
//! use wasm_bindgen::prelude::*;
//! use cfg_if::cfg_if;
//!
//! cfg_if! {
//! if #[cfg(feature = "console_log")] {
//! fn init_log() {
//! use log::Level;
//! console_log::init_with_level(Level::Trace).expect("error initializing log");
//! }
//! } else {
//! fn init_log() {}
//! }
//! }
//!
//! #[wasm_bindgen]
//! pub fn main() {
//! init_log();
//! // ...
//! }
//! ```
//!
//! # Limitations
//!
//! The file and line number information associated with the log messages reports locations from
//! the shims generated by `wasm-bindgen`, not the location of the logger call.
//!
//! [Twiggy]: https://github.com/rustwasm/twiggy
//! [`console_log::log`]: fn.log.html
//! [`fern`]: https://docs.rs/fern
use log::{Log, Level, Record, Metadata, SetLoggerError};
use web_sys::console;
static LOGGER: WebConsoleLogger = WebConsoleLogger {};
struct WebConsoleLogger {}
impl Log for WebConsoleLogger {
fn enabled(&self, metadata: &Metadata) -> bool {
metadata.level() <= log::max_level()
}
fn log(&self, record: &Record) {
if !self.enabled(record.metadata()) {
return;
}
log(record);
}
fn flush(&self) {}
}
/// Print a `log::Record` to the browser's console at the appropriate level.
///
/// This function is useful for integrating with the [`fern`](https://crates.io/crates/fern) logger
/// crate.
///
/// ## Example
/// ```rust,ignore
/// fern::Dispatch::new()
/// .chain(fern::Output::call(console_log::log))
/// .apply()?;
/// ```
pub fn log(record: &Record) {
// pick the console.log() variant for the appropriate logging level
let console_log = match record.level() {
Level::Error => console::error_1,
Level::Warn => console::warn_1,
Level::Info => console::info_1,
Level::Debug => console::log_1,
Level::Trace => console::debug_1,
};
console_log(&format!("{}", record.args()).into());
}
/// Initializes the global logger setting `max_log_level` to the given value.
///
/// ## Example
///
/// ```
/// use log::Level;
/// fn main() {
/// console_log::init_with_level(Level::Debug).expect("error initializing logger");
/// }
/// ```
pub fn init_with_level(level: Level) -> Result<(), SetLoggerError> {
log::set_logger(&LOGGER)?;
log::set_max_level(level.to_level_filter());
Ok(())
}
/// Initializes the global logger with `max_log_level` set to `Level::Info` (a sensible default).
///
/// ## Example
///
/// ```
/// fn main() {
/// console_log::init().expect("error initializing logger");
/// }
/// ```
pub fn init() -> Result<(), SetLoggerError> {
init_with_level(Level::Info)
}