depd

What is depd?

The depd package is a deprecation helper for Node.js. It allows developers to mark functions, properties, and other JavaScript features as deprecated and to issue warning messages when they are used. This can be useful for library authors who want to make changes or remove features without breaking existing code that depends on their libraries.

What are depd's main functionalities?

Deprecate functions

This feature allows you to deprecate a function by wrapping it with a deprecation warning. When the function is called, it will log a deprecation message to the console.

var deprecate = require('depd')('my-module-name');
function oldFunction() {
  deprecate('oldFunction is deprecated, use newFunction instead.');
  // old function code
}

Deprecate property access

This feature allows you to deprecate access to an object property. When the property is accessed, it will log a deprecation message to the console.

var deprecate = require('depd')('my-module-name');
var obj = {};
Object.defineProperty(obj, 'oldProperty', {
  get: function () {
    deprecate('oldProperty is deprecated, use newProperty instead.');
    return 'some value';
  }
});

Customize deprecation messages

This feature allows you to customize the deprecation message for a property to provide additional information or instructions.

var deprecate = require('depd')('my-module-name');
deprecate.property(obj, 'oldProperty', 'oldProperty is deprecated and will be removed in the next major release.');

Other packages similar to depd

deprecate

The deprecate package is similar to depd in that it allows you to mark functions as deprecated. However, it is more lightweight and does not provide the ability to deprecate properties or customize messages to the same extent as depd.

util-deprecate

This package is a Node.js utility for marking deprecated APIs. It is similar to depd but is specifically designed to work with Node.js's built-in 'util' module. It provides a straightforward way to deprecate functions but does not support property deprecation.

README

depd

Deprecate all the things

With great modules comes great responsibility; mark things deprecated!

Install

This module is installed directly using npm:

$ npm install depd

This module can also be bundled with systems like Browserify or webpack, though by default this module will alter it's API to no longer display or track deprecations.

API

var deprecate = require('depd')('my-module')

This library allows you to display deprecation messages to your users. This library goes above and beyond with deprecation warnings by introspection of the call stack (but only the bits that it is interested in).

Instead of just warning on the first invocation of a deprecated function and never again, this module will warn on the first invocation of a deprecated function per unique call site, making it ideal to alert users of all deprecated uses across the code base, rather than just whatever happens to execute first.

The deprecation warnings from this module also include the file and line information for the call into the module that the deprecated function was in.

NOTE this library has a similar interface to the debug module, and this module uses the calling file to get the boundary for the call stacks, so you should always create a new deprecate object in each file and not within some central file.

depd(namespace)

Create a new deprecate function that uses the given namespace name in the messages and will display the call site prior to the stack entering the file this function was called from. It is highly suggested you use the name of your module as the namespace.

deprecate(message)

Call this function from deprecated code to display a deprecation message. This message will appear once per unique caller site. Caller site is the first call site in the stack in a different file from the caller of this function.

If the message is omitted, a message is generated for you based on the site of the deprecate() call and will display the name of the function called, similar to the name displayed in a stack trace.

deprecate.function(fn, message)

Call this function to wrap a given function in a deprecation message on any call to the function. An optional message can be supplied to provide a custom message.

deprecate.property(obj, prop, message)

Call this function to wrap a given property on object in a deprecation message on any accessing or setting of the property. An optional message can be supplied to provide a custom message.

The method must be called on the object where the property belongs (not inherited from the prototype).

If the property is a data descriptor, it will be converted to an accessor descriptor in order to display the deprecation message.

process.on('deprecation', fn)

This module will allow easy capturing of deprecation errors by emitting the errors as the type "deprecation" on the global process. If there are no listeners for this type, the errors are written to STDERR as normal, but if there are any listeners, nothing will be written to STDERR and instead only emitted. From there, you can write the errors in a different format or to a logging source.

The error represents the deprecation and is emitted only once with the same rules as writing to STDERR. The error has the following properties:

• message - This is the message given by the library
• name - This is always 'DeprecationError'
• namespace - This is the namespace the deprecation came from
• stack - This is the stack of the call to the deprecated thing

Example error.stack output:

DeprecationError: my-cool-module deprecated oldfunction
    at Object.<anonymous> ([eval]-wrapper:6:22)
    at Module._compile (module.js:456:26)
    at evalScript (node.js:532:25)
    at startup (node.js:80:7)
    at node.js:902:3

process.env.NO_DEPRECATION

As a user of modules that are deprecated, the environment variable NO_DEPRECATION is provided as a quick solution to silencing deprecation warnings from being output. The format of this is similar to that of DEBUG:

$ NO_DEPRECATION=my-module,othermod node app.js

This will suppress deprecations from being output for "my-module" and "othermod". The value is a list of comma-separated namespaces. To suppress every warning across all namespaces, use the value * for a namespace.

Providing the argument --no-deprecation to the node executable will suppress all deprecations (only available in Node.js 0.8 or higher).

NOTE This will not suppress the deperecations given to any "deprecation" event listeners, just the output to STDERR.

process.env.TRACE_DEPRECATION

As a user of modules that are deprecated, the environment variable TRACE_DEPRECATION is provided as a solution to getting more detailed location information in deprecation warnings by including the entire stack trace. The format of this is the same as NO_DEPRECATION:

$ TRACE_DEPRECATION=my-module,othermod node app.js

This will include stack traces for deprecations being output for "my-module" and "othermod". The value is a list of comma-separated namespaces. To trace every warning across all namespaces, use the value * for a namespace.

Providing the argument --trace-deprecation to the node executable will trace all deprecations (only available in Node.js 0.8 or higher).

NOTE This will not trace the deperecations silenced by NO_DEPRECATION.

Display

When a user calls a function in your library that you mark deprecated, they will see the following written to STDERR (in the given colors, similar colors and layout to the debug module):

bright cyan    bright yellow
|              |          reset       cyan
|              |          |           |
▼              ▼          ▼           ▼
my-cool-module deprecated oldfunction [eval]-wrapper:6:22
▲              ▲          ▲           ▲
|              |          |           |
namespace      |          |           location of mycoolmod.oldfunction() call
               |          deprecation message
               the word "deprecated"

If the user redirects their STDERR to a file or somewhere that does not support colors, they see (similar layout to the debug module):

Sun, 15 Jun 2014 05:21:37 GMT my-cool-module deprecated oldfunction at [eval]-wrapper:6:22
▲                             ▲              ▲          ▲              ▲
|                             |              |          |              |
timestamp of message          namespace      |          |             location of mycoolmod.oldfunction() call
                                             |          deprecation message
                                             the word "deprecated"

Examples

Deprecating all calls to a function

This will display a deprecated message about "oldfunction" being deprecated from "my-module" on STDERR.

var deprecate = require('depd')('my-cool-module')

// message automatically derived from function name
// Object.oldfunction
exports.oldfunction = deprecate.function(function oldfunction () {
  // all calls to function are deprecated
})

// specific message
exports.oldfunction = deprecate.function(function () {
  // all calls to function are deprecated
}, 'oldfunction')

Conditionally deprecating a function call

This will display a deprecated message about "weirdfunction" being deprecated from "my-module" on STDERR when called with less than 2 arguments.

var deprecate = require('depd')('my-cool-module')

exports.weirdfunction = function () {
  if (arguments.length < 2) {
    // calls with 0 or 1 args are deprecated
    deprecate('weirdfunction args < 2')
  }
}

When calling deprecate as a function, the warning is counted per call site within your own module, so you can display different deprecations depending on different situations and the users will still get all the warnings:

var deprecate = require('depd')('my-cool-module')

exports.weirdfunction = function () {
  if (arguments.length < 2) {
    // calls with 0 or 1 args are deprecated
    deprecate('weirdfunction args < 2')
  } else if (typeof arguments[0] !== 'string') {
    // calls with non-string first argument are deprecated
    deprecate('weirdfunction non-string first arg')
  }
}

Deprecating property access

This will display a deprecated message about "oldprop" being deprecated from "my-module" on STDERR when accessed. A deprecation will be displayed when setting the value and when getting the value.

var deprecate = require('depd')('my-cool-module')

exports.oldprop = 'something'

// message automatically derives from property name
deprecate.property(exports, 'oldprop')

// explicit message
deprecate.property(exports, 'oldprop', 'oldprop >= 0.10')

License

MIT