33eb26d6d2
In D220213 we tried to change `Symbol.unscopables` so that it's only supported on syntactic `with` environments (for performance reasons). This failed some WPT tests for event handlers because they use non-syntactic with-environments but have to support `Symbol.unscopables`. This patch adds a `JS::EnvironmentChain` class and uses it instead of an object vector for some JS APIs. This class also lets the embedder specify whether `Symbol.unscopables` must be supported. The `evaluate` shell function now has an option for this too. Differential Revision: https://phabricator.services.mozilla.com/D226139
68 lines
2.3 KiB
C++
68 lines
2.3 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef js_EnvironmentChain_h
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#define js_EnvironmentChain_h
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#include "mozilla/Attributes.h" // MOZ_RAII
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#include <stddef.h> // size_t
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#include "jstypes.h" // JS_PUBLIC_API
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#include "js/GCVector.h" // JS::RootedVector
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struct JS_PUBLIC_API JSContext;
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class JS_PUBLIC_API JSObject;
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namespace JS {
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enum class SupportUnscopables : bool { No = false, Yes = true };
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/**
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* JS::EnvironmentChain stores a list of objects to put on the environment
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* chain.
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*
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* Internally the engine will create a non-syntactic 'with' environment for each
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* of these objects. Note that 'with' environments aren't optimized well so you
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* should use this class only if you really have to.
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*
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* The SupportUnscopables enum class controls whether these non-syntactic 'with'
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* environments support Symbol.unscopables similar to syntactic 'with'
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* statements in JS.
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*
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* Passing SupportUnscopables::No is better for performance because it lets us
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* skip the Symbol.unscopables property lookup. Some Web APIs require supporting
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* Symbol.unscopables though. In Firefox, SupportUnscopables::Yes is used for
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* event handlers.
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*/
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class MOZ_RAII JS_PUBLIC_API EnvironmentChain {
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JS::RootedObjectVector chain_;
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SupportUnscopables supportUnscopables_;
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public:
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EnvironmentChain(JSContext* cx, SupportUnscopables supportUnscopables)
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: chain_(cx), supportUnscopables_(supportUnscopables) {}
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EnvironmentChain(const EnvironmentChain&) = delete;
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void operator=(const EnvironmentChain&) = delete;
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[[nodiscard]] bool append(JSObject* obj) { return chain_.append(obj); }
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bool empty() const { return chain_.empty(); }
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size_t length() const { return chain_.length(); }
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RootedObjectVector& chain() { return chain_; }
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const RootedObjectVector& chain() const { return chain_; }
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void setSupportUnscopables(SupportUnscopables supportUnscopables) {
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supportUnscopables_ = supportUnscopables;
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}
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SupportUnscopables supportUnscopables() const { return supportUnscopables_; }
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};
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} // namespace JS
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#endif /* js_EnvironmentChain_h */
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