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fix global function get polluted close #52 #63

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fix global function get polluted close #52 #63

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adabad6
fix: pollution to outside world Function.prototype.constructor
Jack-Works Jul 22, 2019
7efe73c
test: add test for new behavior of inner Function constructor
Jack-Works Sep 28, 2019
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13 changes: 11 additions & 2 deletions src/repair/functions.js
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Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,6 @@
* a copy has been made, and funtions can only be created by syntax (using eval)
* or by invoking a previously saved reference to the originals.
*/

// todo: this file should be moved out to a separate repo and npm module.
const globalEval = eval;
export function repairFunctions() {
Expand Down Expand Up @@ -46,11 +45,21 @@ export function repairFunctions() {
throw e;
}
const FunctionPrototype = getPrototypeOf(FunctionInstance);
const oldFunctionConstructor = FunctionPrototype.constructor;

function isRunningInRealms() {
const e = new Error().stack;
if (!e) return true;
return e.indexOf('eval') !== -1;
}
// Prevents the evaluation of source when calling constructor on the
// prototype of functions.
const TamedFunction = function() {
throw new TypeError('Not available');
if (isRunningInRealms()) {
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Switching anything semantically significant on the caller is hugely hazardous, and likely is a form of dynamic scoping, which we have taken pains to avoid in the rest of the language. Also, the stack property of Errors is not yet standard, and is likely to change.

Please explain what concrete compatibility problems you are running into, and what you need them to do. Let's see how we can accommodate those cases, or how you can on top of the realms-shim, with minimal damage to the realms-shim itself. Thanks.

throw new TypeError('Not available');
} else {
return oldFunctionConstructor.apply(this, arguments);
}
};
defineProperties(TamedFunction, { name: { value: name } });

Expand Down
101 changes: 91 additions & 10 deletions test/module/functions.js
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Original file line number Diff line number Diff line change
@@ -1,29 +1,70 @@
import test from 'tape';
import { repairFunctions } from '../../src/repair/functions';
import Realm from '../../src/realm';

test('repairFunctions', specs => {
repairFunctions();

specs.test('Function.prototype.constructor', t => {
t.plan(4);
t.plan(7);

// eslint-disable-next-line no-new-func
t.doesNotThrow(() => Function(''));

// eslint-disable-next-line no-proto
t.throws(() => Error.__proto__.constructor(''), TypeError);
t.throws(() => Function.prototype.constructor(''), TypeError);
t.doesNotThrow(() => Error.__proto__.constructor(''));
t.doesNotThrow(() => Function.prototype.constructor(''));

const proto = Object.getPrototypeOf((0, eval)('(function() {})'));
t.throws(() => proto.constructor(''), TypeError);
t.doesNotThrow(() => proto.constructor(''));

const realms = Realm.makeCompartment();

// eslint-disable-next-line no-proto
t.throws(
() => realms.evaluate("Error.__proto__.constructor('')"),
TypeError
);
t.throws(
() => realms.evaluate("Function.prototype.constructor('')"),
TypeError
);

t.throws(
() =>
realms.evaluate(`
const proto = Object.getPrototypeOf((0, eval)('(function() {})'));
proto.constructor('')`),
TypeError
);
});

specs.test('AsyncFunction.constructor', t => {
t.plan(1);
t.plan(2);

try {
const proto = Object.getPrototypeOf((0, eval)('(async function() {})'));
t.throws(() => proto.constructor(''), TypeError);
t.doesNotThrow(() => proto.constructor(''));
} catch (e) {
if (
e instanceof SyntaxError &&
e.message.startsWith('Unexpected token')
) {
t.pass('not supported');
} else {
throw e;
}
}

try {
const realms = Realm.makeCompartment();
t.throws(
() =>
realms.evaluate(`
const proto = Object.getPrototypeOf((0, eval)('(async function() {})'));
proto.constructor('')`),
TypeError
);
} catch (e) {
if (
e instanceof SyntaxError &&
Expand All @@ -37,11 +78,31 @@ test('repairFunctions', specs => {
});

specs.test('GeneratorFunction.constructor', t => {
t.plan(1);
t.plan(2);

try {
const proto = Object.getPrototypeOf((0, eval)('(function* () {})'));
t.throws(() => proto.constructor(''), TypeError);
t.doesNotThrow(() => proto.constructor(''));
} catch (e) {
if (
e instanceof SyntaxError &&
e.message.startsWith('Unexpected token')
) {
t.pass('not supported');
} else {
throw e;
}
}
try {
const realm = Realm.makeCompartment();
t.throws(() =>
realm.evaluate(
`
const proto = Object.getPrototypeOf((0, eval)('(function* () {})'));
proto.constructor('');`,
TypeError
)
);
} catch (e) {
if (
e instanceof SyntaxError &&
Expand All @@ -55,11 +116,31 @@ test('repairFunctions', specs => {
});

specs.test('AsyncGeneratorFunction.constructor', t => {
t.plan(1);
t.plan(2);

try {
const proto = Object.getPrototypeOf((0, eval)('(async function* () {})'));
t.throws(() => proto.constructor(''), TypeError);
t.doesNotThrow(() => proto.constructor(''));
} catch (e) {
if (
e instanceof SyntaxError &&
e.message.startsWith('Unexpected token')
) {
t.pass('not supported');
} else {
throw e;
}
}
try {
const realm = Realm.makeCompartment();
t.throws(
() =>
realm.evaluate(`
const proto = Object.getPrototypeOf((0, eval)('(async function* () {})'));
proto.constructor('');
`),
TypeError
);
} catch (e) {
if (
e instanceof SyntaxError &&
Expand Down