warnings

Warnings allows you to create, disable and output warnings using a simple and easy to manage API.

Installation

This module is released in the public npm registry and can be installed by running:

npm install --save warnings

The --save flag tells npm to add the module and it's installed version to your package.json.

Usage

In all of the examples we assume that you've already required and constructed your first warnings instance as followed:

Basic

'use strict';
 
var warn = require('warnings')('your application');

The first argument is the prefix which all your messages will be prefixed with. It makes sense to use the name of your library here so developers know who is writing these messages. The second argument is optional, see the advanced section for more information the options you can provide there.

Advanced

'use strict';
 
var Warnings = require('warnings')
  , warn = new Warnings('your application', options)

In addition to the API provided in the basic example we also support a constructor format.

The following options are supported:

• stream: The Stream we should write the warnings to. This is the process.stderr by default, but you can also give it a fs.createWriteStream or basically any other stream where the messages should be written in.
• colors: An object with colors we should use in the console. By default we will use an orange-ish for the prefix and white the text content but this can be configured to match the style / colors of your application. You should supply an object with HEX color codes you want to use. This object should contain colors for:
  • prefix, prefix color
  • line, text color If you just want to change one color instead of both of them you can also set these using the prefix and line options.
• atty We want to figure out we're allowed to write colors to the supplied stream so we test it with isatty from the tty module. But this might fail for custom streams you can force this property manually.

warnings.read

Read various of warnings from a json or js file. These files should either export and array with warning objects or an object where the key is name of the warning and the value is the warning object. Please note that this is a sync operation and should only done during the startup phase of your application.

warning spec

A warning object can have the following properties:

• name: The name of the warning on which it's triggered with using the warn.about(name) method. You don't need to set this property if you supply an object instead of an array of warnings as we will use the key for the name instead.
• message: Actual message that needs to be written to the user. It can be a string (with new lines) or an array with multiple lines. Try to limit your self to the amount of chars per line as not everybody will sit behind big ass monitors.
• conditional: Allows you to only execute this message when it passes a truth test. This value can be set to a:
  • function: It will receive the second argument from the warn.about method as argument and should return a boolean as indication if the message should be shown.
  • regexp: A regexp where the second argument of warn.about should be tested against.
  • anything else: This will be tested using a simple === test, where it will be compared with the second argument of the warn.about call.

warn.read(path.join(__dirname, 'warnings.json'))
    .read(path.join(__dirname, 'warnings.js'));

warnings.set

Manually set warnings. This method requires 2 arguments:

1. The name on which we should trigger the message. This should be the same value as you pass in to the warn.about method as first argument.
2. Either a string or array which would be the message that gets outputted or an object that follows warning spec as mentioned above.

warn.set('https', 'Please supply a HTTPS instead of a HTTP server.');
warn.set('https', {
  message: 'Using a HTTPS servers instead of a HTTP server will prevent connection blocking',
  conditional: function check(server) {
    return !(server instanceOf require('https').Server);
  }
});

warnings.about

Trigger the messages based on the provided name. This method accepts 2 arguments:

1. The name of the message should be triggered.
2. A value that is needed to pass the conditional truth test of the specified message.

The method will return a boolean as indication if a message was outputted. If you supply it with an unknown, disabled name or fail to pass the conditional test of a message it will return false or will output the returned value of the stream.write.

We will automatically remove the message that we're outputting to prevent messages from being displayed twice. Informing the users is nice, but the spamming isn't ;-).

warn.about('https', require('http').createServer());
warn.about('name-here', 1313);
warn.about('subject');

warnings.disable

Suppress warnings from being written. This would still allow you to call warn.about(name) in your code but it just returns false and will not write anything to the console. The disable method accepts a bunch of different ways for disabling messages.

warn.disable('foo').disable('bar');
warn.disable('foo', 'bar');
warn.disable({foo: 1, bar: 'what ever' });
warn.disable(['foo', 'bar']);

So pick what ever suites your needs.

warnings.destroy

Completely kill the instance and remove all internal references so we can free up memory again. The method will return a boolean indicating if a destruction was successful.

warn.destroy();

License

MIT