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11 Deprecate all the things
13 > With great modules comes great responsibility; mark things deprecated!
24 var deprecate = require('depd')('my-module')
27 This library allows you to display deprecation messages to your users.
28 This library goes above and beyond with deprecation warnings by
29 introspection of the call stack (but only the bits that it is interested
32 Instead of just warning on the first invocation of a deprecated
33 function and never again, this module will warn on the first invocation
34 of a deprecated function per unique call site, making it ideal to alert
35 users of all deprecated uses across the code base, rather than just
36 whatever happens to execute first.
38 The deprecation warnings from this module also include the file and line
39 information for the call into the module that the deprecated function was
42 **NOTE** this library has a similar interface to the `debug` module, and
43 this module uses the calling file to get the boundary for the call stacks,
44 so you should always create a new `deprecate` object in each file and not
45 within some central file.
49 Create a new deprecate function that uses the given namespace name in the
50 messages and will display the call site prior to the stack entering the
51 file this function was called from. It is highly suggested you use the
52 name of your module as the namespace.
54 ### deprecate(message)
56 Call this function from deprecated code to display a deprecation message.
57 This message will appear once per unique caller site. Caller site is the
58 first call site in the stack in a different file from the caller of this
61 If the message is omitted, a message is generated for you based on the site
62 of the `deprecate()` call and will display the name of the function called,
63 similar to the name displayed in a stack trace.
65 ### deprecate.function(fn, message)
67 Call this function to wrap a given function in a deprecation message on any
68 call to the function. An optional message can be supplied to provide a custom
71 ### deprecate.property(obj, prop, message)
73 Call this function to wrap a given property on object in a deprecation message
74 on any accessing or setting of the property. An optional message can be supplied
75 to provide a custom message.
77 The method must be called on the object where the property belongs (not
78 inherited from the prototype).
80 If the property is a data descriptor, it will be converted to an accessor
81 descriptor in order to display the deprecation message.
83 ### process.on('deprecation', fn)
85 This module will allow easy capturing of deprecation errors by emitting the
86 errors as the type "deprecation" on the global `process`. If there are no
87 listeners for this type, the errors are written to STDERR as normal, but if
88 there are any listeners, nothing will be written to STDERR and instead only
89 emitted. From there, you can write the errors in a different format or to a
92 The error represents the deprecation and is emitted only once with the same
93 rules as writing to STDERR. The error has the following properties:
95 - `message` - This is the message given by the library
96 - `name` - This is always `'DeprecationError'`
97 - `namespace` - This is the namespace the deprecation came from
98 - `stack` - This is the stack of the call to the deprecated thing
100 Example `error.stack` output:
103 DeprecationError: my-cool-module deprecated oldfunction
104 at Object.<anonymous> ([eval]-wrapper:6:22)
105 at Module._compile (module.js:456:26)
106 at evalScript (node.js:532:25)
107 at startup (node.js:80:7)
111 ### process.env.NO_DEPRECATION
113 As a user of modules that are deprecated, the environment variable `NO_DEPRECATION`
114 is provided as a quick solution to silencing deprecation warnings from being
115 output. The format of this is similar to that of `DEBUG`:
118 $ NO_DEPRECATION=my-module,othermod node app.js
121 This will suppress deprecations from being output for "my-module" and "othermod".
122 The value is a list of comma-separated namespaces. To suppress every warning
123 across all namespaces, use the value `*` for a namespace.
125 Providing the argument `--no-deprecation` to the `node` executable will suppress
126 all deprecations (only available in Node.js 0.8 or higher).
128 **NOTE** This will not suppress the deperecations given to any "deprecation"
129 event listeners, just the output to STDERR.
131 ### process.env.TRACE_DEPRECATION
133 As a user of modules that are deprecated, the environment variable `TRACE_DEPRECATION`
134 is provided as a solution to getting more detailed location information in deprecation
135 warnings by including the entire stack trace. The format of this is the same as
139 $ TRACE_DEPRECATION=my-module,othermod node app.js
142 This will include stack traces for deprecations being output for "my-module" and
143 "othermod". The value is a list of comma-separated namespaces. To trace every
144 warning across all namespaces, use the value `*` for a namespace.
146 Providing the argument `--trace-deprecation` to the `node` executable will trace
147 all deprecations (only available in Node.js 0.8 or higher).
149 **NOTE** This will not trace the deperecations silenced by `NO_DEPRECATION`.
153 ![message](files/message.png)
155 When a user calls a function in your library that you mark deprecated, they
156 will see the following written to STDERR (in the given colors, similar colors
157 and layout to the `debug` module):
160 bright cyan bright yellow
164 my-cool-module deprecated oldfunction [eval]-wrapper:6:22
167 namespace | | location of mycoolmod.oldfunction() call
168 | deprecation message
169 the word "deprecated"
172 If the user redirects their STDERR to a file or somewhere that does not support
173 colors, they see (similar layout to the `debug` module):
176 Sun, 15 Jun 2014 05:21:37 GMT my-cool-module deprecated oldfunction at [eval]-wrapper:6:22
179 timestamp of message namespace | | location of mycoolmod.oldfunction() call
180 | deprecation message
181 the word "deprecated"
186 ### Deprecating all calls to a function
188 This will display a deprecated message about "oldfunction" being deprecated
189 from "my-module" on STDERR.
192 var deprecate = require('depd')('my-cool-module')
194 // message automatically derived from function name
195 // Object.oldfunction
196 exports.oldfunction = deprecate.function(function oldfunction() {
197 // all calls to function are deprecated
201 exports.oldfunction = deprecate.function(function () {
202 // all calls to function are deprecated
206 ### Conditionally deprecating a function call
208 This will display a deprecated message about "weirdfunction" being deprecated
209 from "my-module" on STDERR when called with less than 2 arguments.
212 var deprecate = require('depd')('my-cool-module')
214 exports.weirdfunction = function () {
215 if (arguments.length < 2) {
216 // calls with 0 or 1 args are deprecated
217 deprecate('weirdfunction args < 2')
222 When calling `deprecate` as a function, the warning is counted per call site
223 within your own module, so you can display different deprecations depending
224 on different situations and the users will still get all the warnings:
227 var deprecate = require('depd')('my-cool-module')
229 exports.weirdfunction = function () {
230 if (arguments.length < 2) {
231 // calls with 0 or 1 args are deprecated
232 deprecate('weirdfunction args < 2')
233 } else if (typeof arguments[0] !== 'string') {
234 // calls with non-string first argument are deprecated
235 deprecate('weirdfunction non-string first arg')
240 ### Deprecating property access
242 This will display a deprecated message about "oldprop" being deprecated
243 from "my-module" on STDERR when accessed. A deprecation will be displayed
244 when setting the value and when getting the value.
247 var deprecate = require('depd')('my-cool-module')
249 exports.oldprop = 'something'
251 // message automatically derives from property name
252 deprecate.property(exports, 'oldprop')
255 deprecate.property(exports, 'oldprop', 'oldprop >= 0.10')
262 [npm-version-image]: https://img.shields.io/npm/v/depd.svg
263 [npm-downloads-image]: https://img.shields.io/npm/dm/depd.svg
264 [npm-url]: https://npmjs.org/package/depd
265 [travis-image]: https://img.shields.io/travis/dougwilson/nodejs-depd/master.svg?label=linux
266 [travis-url]: https://travis-ci.org/dougwilson/nodejs-depd
267 [appveyor-image]: https://img.shields.io/appveyor/ci/dougwilson/nodejs-depd/master.svg?label=windows
268 [appveyor-url]: https://ci.appveyor.com/project/dougwilson/nodejs-depd
269 [coveralls-image]: https://img.shields.io/coveralls/dougwilson/nodejs-depd/master.svg
270 [coveralls-url]: https://coveralls.io/r/dougwilson/nodejs-depd?branch=master
271 [node-image]: https://img.shields.io/node/v/depd.svg
272 [node-url]: http://nodejs.org/download/
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