1aa51b498e
This is a reland of 29c1eab92e
Original change's description:
> [builtins] Clean up the use of class_name / ES5 [[Class]]
>
> Before ES2015, the ES spec had a [[Class]] internal slot for all
> objects, which Object.prototype.toString() would use to figure the
> returned string. Post-ES2015, the [[Class]] slot was removed in spec for
> all objects, with the @@toStringTag well-known symbol the proper way to
> change Object.prototype.toString() output.
>
> At the time, spec-identical handling without the use of [[Class]] was
> implemented in V8 for all objects other than API objects, where issues
> with the Web IDL spec [1] prevented Blink, and hence V8, to totally
> migrate to @@toStringTag. However, since 2016 [2] Blink has been setting
> @@toStringTag on API class prototypes to manage the
> Object.prototype.toString() output, so the legacy [[Class]] handling in
> V8 has not been necessary for the past couple of years.
>
> This CL removes the remaining legacy [[Class]] handling in
> Object.prototype.toString(), JSReceiver::class_name(), and
> GetConstructorName(). However, it does not remove the class_name field
> in FunctionTemplateInfo, as it is still used for the `name` property of
> created functions.
>
> This CL also cleans up other places in the codebase that still reference
> [[Class]].
>
> This change should have minimal impact on web-compatibility. For the
> change to be observable, a script must do one of the following:
>
> 1. delete APIConstructor.prototype[Symbol.toStringTag];
> 2. Object.setPrototypeOf(apiObject, somethingElse);
>
> Before this CL, these changes will not change the apiObject.toString()
> output. But after this CL, they will make apiObject.toString() show
> "[object Object]" (in the first case) or the @@toStringTag of the other
> prototype (in the latter case).
>
> However, both are deemed unlikely. @@toStringTag is not well-known
> feature of JavaScript, nor does it get tampered much on API
> constructors. In the second case, setting the prototype of an API object
> would effectly render the object useless, as all its methods (including
> property getters/setters) would no longer be accessible.
>
> Currently, @@toStringTag-based API object branding is not yet
> implemented by other browsers. This V8 bug in particular has been an
> impediment to standardizing toString behavior. Fixing this bug will
> unblock [3] and lead to a better Web IDL spec, and better toString()
> compatibility for all.
>
> [1]: https://www.w3.org/Bugs/Public/show_bug.cgi?id=28244
> [2]: https://crrev.com/909c0d7d5a53c8526ded351683c65ea7d17531d4
> [3]: https://github.com/heycam/webidl/pull/357
>
> Bug: chromium:793406
> Cq-Include-Trybots: luci.chromium.try:linux-rel
> Change-Id: Iceded24e37afa2646ec385d5018909f55b177f93
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2146996
> Commit-Queue: Timothy Gu <timothygu@chromium.org>
> Reviewed-by: Toon Verwaest <verwaest@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#67327}
Bug: chromium:793406
Change-Id: Ia5d97bd4e1c44cadc6f18a17ffc9d06b038cf8f1
Cq-Include-Trybots: luci.chromium.try:linux-rel
Cq-Include-Trybots: luci.v8.try:v8_linux_blink_rel
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2163881
Auto-Submit: Timothy Gu <timothygu@chromium.org>
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67361}
51 lines
2.3 KiB
JavaScript
51 lines
2.3 KiB
JavaScript
// Copyright 2008 the V8 project authors. All rights reserved.
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following
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// disclaimer in the documentation and/or other materials provided
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// with the distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived
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// from this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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// Object.prototype.toString should return the correct values for instances of
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// various built-in classes.
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var funs = {
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Object: [ Object ],
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Function: [ Function ],
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Array: [ Array ],
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String: [ String ],
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Boolean: [ Boolean ],
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Number: [ Number ],
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Date: [ Date ],
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RegExp: [ RegExp ],
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Error: [ Error, TypeError, RangeError, SyntaxError, ReferenceError, EvalError, URIError ]
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}
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for (f in funs) {
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for (i in funs[f]) {
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assertEquals("[object " + f + "]",
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Object.prototype.toString.call(new funs[f][i]),
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funs[f][i]);
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assertEquals("[object Function]",
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Object.prototype.toString.call(funs[f][i]),
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funs[f][i]);
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}
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}
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