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util: make inherits work with classes #3455

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merged 1 commit into from Oct 27, 2015

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targos commented Oct 20, 2015

Fixes: #3452

@targos targos added the util label Oct 20, 2015

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test/parallel/test-util.js Outdated
assert.throws(function() { util.inherits(null, ctor); }, TypeError);
assert.doesNotThrow(function() { util.inherits(ctor, ctor); }, TypeError);
assert.throws(function() { util.inherits(null, superCtor); }, TypeError);
assert.doesNotThrow(function() { util.inherits(ctor, superCtor); }, TypeError);

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targos Oct 20, 2015

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Reason for this change:

> function A(){}
undefined
> util.inherits(A, A)
TypeError: Cyclic __proto__ value
    at Function.setPrototypeOf (native)
    at Object.exports.inherits (util.js:764:10)
...

It doesn't make sense to make a function inherit from itself, but I guess it's still a semver-major change?

@targos targos force-pushed the targos:fix-inherits-class branch Oct 20, 2015

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targos commented Oct 20, 2015

updated the commit message

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bnoordhuis commented Oct 20, 2015

LGTM but more eyeballs are warranted. This PR changes C.prototype = Object.create(P.prototype) to C.prototype.__proto__ = P.prototype and that probably has subtle implications. R=@domenic maybe?

Apropos the commit log:

It is not allowed with ES2015 classes because the prototype property is read only.

Maybe add "in strict mode". Sloppy mode still lets you assign.

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jasnell commented Oct 20, 2015

It looks good on initial look through but needs more tests.

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targos commented Oct 20, 2015

Maybe add "in strict mode". Sloppy mode still lets you assign.

It doesn't throw when you try to assign, but it is a no-op:

class A{}
A.prototype = null;
console.log(A.prototype);
> node --harmony-sloppy test.js
A {}
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bnoordhuis commented Oct 20, 2015

Oh, good point. Never mind then.

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domenic commented Oct 22, 2015

As long as this is marked semver-major, it seems like a good change. It does have some subtle implications but all in the right direction.

@targos targos force-pushed the targos:fix-inherits-class branch Oct 26, 2015

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targos commented Oct 26, 2015

Rebased on master and updated tests. PTAL
CI: https://ci.nodejs.org/job/node-test-commit/971/

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thefourtheye commented Oct 26, 2015

LGTM

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targos commented Oct 26, 2015

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jasnell commented Oct 26, 2015

LGTM

util: make inherits work with classes
The current implementation overwrites the prototype of the target
constructor. It is not allowed with ES2015 classes because the prototype
property is read only. Use Object.setPrototypeOf instead.

Fixes: #3452
PR-URL: #3455
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

@targos targos force-pushed the targos:fix-inherits-class branch to 29da8cf Oct 27, 2015

@targos targos merged commit 29da8cf into nodejs:master Oct 27, 2015

@targos targos deleted the targos:fix-inherits-class branch Oct 27, 2015

rvagg added a commit to rvagg/io.js that referenced this pull request Oct 29, 2015

util: make inherits work with classes
The current implementation overwrites the prototype of the target
constructor. It is not allowed with ES2015 classes because the prototype
property is read only. Use Object.setPrototypeOf instead.

Fixes: nodejs#3452
PR-URL: nodejs#3455
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

@rvagg rvagg referenced this pull request Oct 29, 2015

Merged

Release proposal: v5.0.0 #3466

rvagg added a commit to rvagg/io.js that referenced this pull request Oct 29, 2015

2015-10-29, Version 5.0.0 (Stable)
Notable changes:

* buffer: (Breaking) Removed both 'raw' and 'raws' encoding types from Buffer,
  these have been deprecated for a long time (Sakthipriyan Vairamani) nodejs#2859.
* console: (Breaking) Values reported by console.time() now have 3 decimals of
  accuracy added (Michaël Zasso) nodejs#3166.
* fs:
  - fs.readFile*(), fs.writeFile*(), and fs.appendFile*() now also accept a file
    descriptor as their first argument (Johannes Wüller) nodejs#3163.
  - (Breaking) In fs.readFile(), if an encoding is specified and the internal
    toString() fails the error is no longer thrown but is passed to the callback
    (Evan Lucas) nodejs#3485.
  - (Breaking) In fs.read() (using the fs.read(fd, length, position, encoding,
    callback) form), if the internal toString() fails the error is no longer
    thrown but is passed to the callback (Evan Lucas) nodejs#3503.
* http:
  - Fixed a bug where pipelined http requests would stall (Fedor Indutny) nodejs#3342.
  - (Breaking) When parsing HTTP, don't add duplicates of the following headers:
    Retry-After, ETag, Last-Modified, Server, Age, Expires. This is in addition
    to the following headers which already block duplicates: Content-Type,
    Content-Length, User-Agent, Referer, Host, Authorization,
    Proxy-Authorization, If-Modified-Since, If-Unmodified-Since, From, Location,
    Max-Forwards (James M Snell) nodejs#3090.
  - (Breaking) The callback argument to OutgoingMessage#setTimeout() must be a
    function or a TypeError is thrown (James M Snell) nodejs#3090.
  - (Breaking) HTTP methods and header names must now conform to the RFC 2616
    "token" rule, a list of allowed characters that excludes control characters
    and a number of separator characters. Specifically, methods and header names
    must now match /^[a-zA-Z0-9_!#$%&'*+.^`|~-]+$/ or a TypeError will be thrown
    (James M Snell) nodejs#2526.
* node:
  - (Breaking) Deprecated the _linklist module (Rich Trott) nodejs#3078.
  - (Breaking) Removed require.paths and require.registerExtension(), both had
    been previously set to throw Error when accessed
    (Sakthipriyan Vairamani) nodejs#2922.
* npm: Upgraded to version 3.3.6 from 2.14.7, see
  https://github.com/npm/npm/releases/tag/v3.3.6 for more details. This is a
  major version bump for npm and it has seen a significant amount of change.
  Please see the original npm v3.0.0 release notes for a list of major changes
  (Rebecca Turner) nodejs#3310.
* src: (Breaking) Bumped NODE_MODULE_VERSION to 47 from 46, this is necessary
  due to the V8 upgrade. Native add-ons will need to be recompiled
  (Rod Vagg) nodejs#3400.
* timers: Attempt to reuse the timer handle for setTimeout().unref(). This fixes
  a long-standing known issue where unrefed timers would perviously hold
  beforeExit open (Fedor Indutny) nodejs#3407.
* tls:
  - Added ALPN Support (Shigeki Ohtsu) nodejs#2564.
  - TLS options can now be passed in an object to createSecurePair()
    (Коренберг Марк) nodejs#2441.
  - (Breaking) The default minimum DH key size for tls.connect() is now 1024
    bits and a warning is shown when DH key size is less than 2048 bits. This a security consideration to prevent "logjam" attacks. A new minDHSize TLS
    option can be used to override the default. (Shigeki Ohtsu) nodejs#1831.
* util:
  - (Breaking) util.p() was deprecated for years, and has now been removed
    (Wyatt Preul) nodejs#3432.
  - (Breaking) util.inherits() can now work with ES6 classes. This is considered
    a breaking change because of potential subtle side-effects caused by a
    change from directly reassigning the prototype of the constructor using
    `ctor.prototype = Object.create(superCtor.prototype, { constructor: { ... } })`
    to using `Object.setPrototypeOf(ctor.prototype, superCtor.prototype)`
    (Michaël Zasso) nodejs#3455.
* v8: (Breaking) Upgraded to 4.6.85.25 from 4.5.103.35 (Ali Ijaz Sheikh) nodejs#3351.
  - Implements the spread operator, see
    https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_operator
    for further information.
  - Implements new.target, see
    https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/new.target
    for further information.
* zlib: Decompression now throws on truncated input (e.g. unexpected end of
  file) (Yuval Brik) nodejs#2595.

PR-URL: nodejs#3466

rvagg added a commit that referenced this pull request Oct 29, 2015

2015-10-29, Version 5.0.0 (Stable)
Notable changes:

* buffer: (Breaking) Removed both 'raw' and 'raws' encoding types from Buffer,
  these have been deprecated for a long time (Sakthipriyan Vairamani) #2859.
* console: (Breaking) Values reported by console.time() now have 3 decimals of
  accuracy added (Michaël Zasso) #3166.
* fs:
  - fs.readFile*(), fs.writeFile*(), and fs.appendFile*() now also accept a file
    descriptor as their first argument (Johannes Wüller) #3163.
  - (Breaking) In fs.readFile(), if an encoding is specified and the internal
    toString() fails the error is no longer thrown but is passed to the callback
    (Evan Lucas) #3485.
  - (Breaking) In fs.read() (using the fs.read(fd, length, position, encoding,
    callback) form), if the internal toString() fails the error is no longer
    thrown but is passed to the callback (Evan Lucas) #3503.
* http:
  - Fixed a bug where pipelined http requests would stall (Fedor Indutny) #3342.
  - (Breaking) When parsing HTTP, don't add duplicates of the following headers:
    Retry-After, ETag, Last-Modified, Server, Age, Expires. This is in addition
    to the following headers which already block duplicates: Content-Type,
    Content-Length, User-Agent, Referer, Host, Authorization,
    Proxy-Authorization, If-Modified-Since, If-Unmodified-Since, From, Location,
    Max-Forwards (James M Snell) #3090.
  - (Breaking) The callback argument to OutgoingMessage#setTimeout() must be a
    function or a TypeError is thrown (James M Snell) #3090.
  - (Breaking) HTTP methods and header names must now conform to the RFC 2616
    "token" rule, a list of allowed characters that excludes control characters
    and a number of separator characters. Specifically, methods and header names
    must now match /^[a-zA-Z0-9_!#$%&'*+.^`|~-]+$/ or a TypeError will be thrown
    (James M Snell) #2526.
* node:
  - (Breaking) Deprecated the _linklist module (Rich Trott) #3078.
  - (Breaking) Removed require.paths and require.registerExtension(), both had
    been previously set to throw Error when accessed
    (Sakthipriyan Vairamani) #2922.
* npm: Upgraded to version 3.3.6 from 2.14.7, see
  https://github.com/npm/npm/releases/tag/v3.3.6 for more details. This is a
  major version bump for npm and it has seen a significant amount of change.
  Please see the original npm v3.0.0 release notes for a list of major changes
  (Rebecca Turner) #3310.
* src: (Breaking) Bumped NODE_MODULE_VERSION to 47 from 46, this is necessary
  due to the V8 upgrade. Native add-ons will need to be recompiled
  (Rod Vagg) #3400.
* timers: Attempt to reuse the timer handle for setTimeout().unref(). This fixes
  a long-standing known issue where unrefed timers would perviously hold
  beforeExit open (Fedor Indutny) #3407.
* tls:
  - Added ALPN Support (Shigeki Ohtsu) #2564.
  - TLS options can now be passed in an object to createSecurePair()
    (Коренберг Марк) #2441.
  - (Breaking) The default minimum DH key size for tls.connect() is now 1024
    bits and a warning is shown when DH key size is less than 2048 bits. This a security consideration to prevent "logjam" attacks. A new minDHSize TLS
    option can be used to override the default. (Shigeki Ohtsu) #1831.
* util:
  - (Breaking) util.p() was deprecated for years, and has now been removed
    (Wyatt Preul) #3432.
  - (Breaking) util.inherits() can now work with ES6 classes. This is considered
    a breaking change because of potential subtle side-effects caused by a
    change from directly reassigning the prototype of the constructor using
    `ctor.prototype = Object.create(superCtor.prototype, { constructor: { ... } })`
    to using `Object.setPrototypeOf(ctor.prototype, superCtor.prototype)`
    (Michaël Zasso) #3455.
* v8: (Breaking) Upgraded to 4.6.85.25 from 4.5.103.35 (Ali Ijaz Sheikh) #3351.
  - Implements the spread operator, see
    https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_operator
    for further information.
  - Implements new.target, see
    https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/new.target
    for further information.
* zlib: Decompression now throws on truncated input (e.g. unexpected end of
  file) (Yuval Brik) #2595.

PR-URL: #3466
@mgtitimoli

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mgtitimoli commented Feb 9, 2016

This PR didn't fulfill what it was trying to achieve: make inherits work with classes, since the only thing that was done here, is the replacement of Object.create by the use of Object.setPrototypeOf, so it is doing exactly the same as before.

Instead of having removed the Object.create call, another statement like the following one should have been added:

Object.setPrototypeOf(ctor, superCtor);

Since what I wrote above would enable the inherits between classes and not only instances.

Despite the fact that there is an extra if, and a bad use of the ternary operator, below is the Babel implementation:

image

And as you can see they are doing exactly what I wrote before in the line 19.

// ES6 classes can inherit from a constructor function
class E {
constructor() {
D.call(this);

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@syrnick

syrnick May 4, 2016

Would this be better written as E.super_.call(this) ? That decouples E's constructor from the inherits in ln67.

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