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lib: use null-prototype objects for property descriptors #43270

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merged 3 commits into from
Jun 3, 2022
Merged

lib: use null-prototype objects for property descriptors #43270

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ed9c8b5
lib: use null-prototype objects for property descriptors
aduh95 May 25, 2022
5d0986a
fixup! lib: use null-prototype objects for property descriptors
aduh95 Jun 1, 2022
265a4f1
fixup! fixup! lib: use null-prototype objects for property descriptors
aduh95 Jun 1, 2022
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81 changes: 42 additions & 39 deletions lib/internal/encoding.js
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Original file line number Diff line number Diff line change
Expand Up @@ -4,12 +4,11 @@
// https://encoding.spec.whatwg.org

const {
ArrayPrototypeMap,
ObjectCreate,
ObjectDefineProperties,
ObjectEntries,
ObjectFromEntries,
ObjectGetOwnPropertyDescriptors,
ObjectSetPrototypeOf,
ObjectValues,
SafeMap,
StringPrototypeSlice,
Symbol,
Expand Down Expand Up @@ -533,48 +532,52 @@ function makeTextDecoderJS() {
}

// Mix in some shared properties.
ObjectDefineProperties(
TextDecoder.prototype,
ObjectFromEntries(ArrayPrototypeMap(ObjectEntries(ObjectGetOwnPropertyDescriptors({
get encoding() {
validateDecoder(this);
return this[kEncoding];
},

get fatal() {
validateDecoder(this);
return (this[kFlags] & CONVERTER_FLAGS_FATAL) === CONVERTER_FLAGS_FATAL;
},

get ignoreBOM() {
validateDecoder(this);
return (this[kFlags] & CONVERTER_FLAGS_IGNORE_BOM) ===
const sharedProperties = ObjectGetOwnPropertyDescriptors({
get encoding() {
validateDecoder(this);
return this[kEncoding];
},

get fatal() {
validateDecoder(this);
return (this[kFlags] & CONVERTER_FLAGS_FATAL) === CONVERTER_FLAGS_FATAL;
},

get ignoreBOM() {
validateDecoder(this);
return (this[kFlags] & CONVERTER_FLAGS_IGNORE_BOM) ===
CONVERTER_FLAGS_IGNORE_BOM;
},
},

[inspect](depth, opts) {
validateDecoder(this);
if (typeof depth === 'number' && depth < 0)
return this;
const constructor = getConstructorOf(this) || TextDecoder;
const obj = ObjectCreate({ constructor });
obj.encoding = this.encoding;
obj.fatal = this.fatal;
obj.ignoreBOM = this.ignoreBOM;
if (opts.showHidden) {
obj[kFlags] = this[kFlags];
obj[kHandle] = this[kHandle];
}
// Lazy to avoid circular dependency
const { inspect } = require('internal/util/inspect');
return `${constructor.name} ${inspect(obj)}`;
[inspect](depth, opts) {
validateDecoder(this);
if (typeof depth === 'number' && depth < 0)
return this;
const constructor = getConstructorOf(this) || TextDecoder;
const obj = ObjectCreate({ constructor });
obj.encoding = this.encoding;
obj.fatal = this.fatal;
obj.ignoreBOM = this.ignoreBOM;
if (opts.showHidden) {
obj[kFlags] = this[kFlags];
obj[kHandle] = this[kHandle];
}
})), ({ 0: key, 1: desc }) => [key, { __proto__: null, ...desc }]))
);
// Lazy to avoid circular dependency
const { inspect } = require('internal/util/inspect');
return `${constructor.name} ${inspect(obj)}`;
}
});
const propertiesValues = ObjectValues(sharedProperties);
for (let i = 0; i < propertiesValues.length; i++) {
// We want to use null-prototype objects to not rely on globally mutable
// %Object.prototype%.
ObjectSetPrototypeOf(propertiesValues[i], null);
}
sharedProperties[inspect].enumerable = false;
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why mutate it instead of spreading it in like below?:

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@aduh95 aduh95 Jun 1, 2022 •
edited
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Why not mutate it instead? If mutating is not an option, I think I'd prefer ObjectDefineProperty(TextDecoder.prototype, inspect, { __proto__: null, enumerable: false }); over your suggestion.

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mutation is something that both slows things down (by changing the object's shape) and is also conceptually distasteful, so in general it's nicer to create objects wholesale rather than ever altering one.

go with whatever you prefer, obviously

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Unless someone else wants to take a side, I think I'm going to keep it as is. I'm fine with whichever solution, but mutating sharedProperties seems the most natural to me in this instance.


ObjectDefineProperties(TextDecoder.prototype, {
decode: kEnumerableProperty,
[inspect]: { __proto__: null, enumerable: false },
...sharedProperties,
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Suggested change
...sharedProperties,
...sharedProperties,
[inspect]: { __proto__: null, ...sharedProperties[inspect], enumerable: false },

[SymbolToStringTag]: {
__proto__: null,
configurable: true,
Expand Down
17 changes: 9 additions & 8 deletions lib/internal/worker/js_transferable.js
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Original file line number Diff line number Diff line change
@@ -1,13 +1,11 @@
'use strict';
const {
ArrayPrototypeMap,
Error,
ObjectDefineProperties,
ObjectEntries,
ObjectFromEntries,
ObjectGetOwnPropertyDescriptors,
ObjectGetPrototypeOf,
ObjectSetPrototypeOf,
ObjectValues,
ReflectConstruct,
StringPrototypeSplit,
} = primordials;
Expand Down Expand Up @@ -43,11 +41,14 @@ function setup() {

function makeTransferable(obj) {
const inst = ReflectConstruct(JSTransferable, [], obj.constructor);
ObjectDefineProperties(inst,
ObjectFromEntries(ArrayPrototypeMap(
ObjectEntries(ObjectGetOwnPropertyDescriptors(obj)),
({ 0: key, 1: desc }) => [key, { __proto__: null, ...desc }]
)));
const properties = ObjectGetOwnPropertyDescriptors(obj);
const propertiesValues = ObjectValues(properties);
for (let i = 0; i < propertiesValues.length; i++) {
// We want to use null-prototype objects to not rely on globally mutable
// %Object.prototype%.
ObjectSetPrototypeOf(propertiesValues[i], null);
}
ObjectDefineProperties(inst, properties);
ObjectSetPrototypeOf(inst, ObjectGetPrototypeOf(obj));
return inst;
}
Expand Down