90 lines
3 KiB
Markdown
90 lines
3 KiB
Markdown
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# proc-log
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Emits 'log' events on the process object which a log output listener can
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consume and print to the terminal.
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This is used by various modules within the npm CLI stack in order to send
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log events that can be consumed by a listener on the process object.
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## API
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* `log.error(...args)` calls `process.emit('log', 'error', ...args)`
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The highest log level. For printing extremely serious errors that
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indicate something went wrong.
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* `log.warn(...args)` calls `process.emit('log', 'warn', ...args)`
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A fairly high log level. Things that the user needs to be aware of, but
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which won't necessarily cause improper functioning of the system.
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* `log.notice(...args)` calls `process.emit('log', 'notice', ...args)`
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Notices which are important, but not necessarily dangerous or a cause for
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excess concern.
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* `log.info(...args)` calls `process.emit('log', 'info', ...args)`
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Informative messages that may benefit the user, but aren't particularly
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important.
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* `log.verbose(...args)` calls `process.emit('log', 'verbose', ...args)`
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Noisy output that is more detail that most users will care about.
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* `log.silly(...args)` calls `process.emit('log', 'silly', ...args)`
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Extremely noisy excessive logging messages that are typically only useful
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for debugging.
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* `log.http(...args)` calls `process.emit('log', 'http', ...args)`
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Information about HTTP requests made and/or completed.
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* `log.pause()` calls `process.emit('log', 'pause')` Used to tell
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the consumer to stop printing messages.
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* `log.resume()` calls `process.emit('log', 'resume')`
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Used to tell the consumer that it is ok to print messages again.
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* `log.LEVELS` an array of strings of all log method names
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## Examples
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Every method calls `process.emit('log', level, ...otherArgs)` internally.
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So in order to consume those events you need to do `process.on('log', fn)`.
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### Colorize based on level
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Here's an example of how to consume `proc-log` events and colorize them
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based on level:
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```js
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const chalk = require('chalk')
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process.on('log', (level, ...args) => {
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if (level === 'error') {
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console.log(chalk.red(level), ...args)
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} else {
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console.log(chalk.blue(level), ...args)
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}
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})
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```
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### Pause and resume
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`pause` and `resume` are included so you have the ability to tell your consumer
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that you want to pause or resume your display of logs. In the npm CLI we use
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this to buffer all logs on init until we know the correct loglevel to display.
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But we also setup a second handler that writes everything to a file even if
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paused.
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```js
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let paused = true
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const buffer = []
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// this handler will buffer and replay logs only
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// after `procLog.resume()` is called
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process.on('log', (level, ...args) => {
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if (level === 'resume') {
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buffer.forEach((item) => console.log(...item))
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paused = false
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return
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}
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if (paused) {
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buffer.push([level, ...args])
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} else {
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console.log(level, ...args)
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}
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})
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// this handler will write everything to a file
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process.on('log', (...args) => {
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fs.appendFileSync('debug.log', args.join(' '))
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})
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```
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