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util: never trigger proxy traps while inspecting objects #30767

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2 changes: 2 additions & 0 deletions benchmark/util/format.js
Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,8 @@ const inputs = {
'no-replace-2': ['foobar', 'yeah', 'mensch', 5],
'only-objects': [{ msg: 'This is an error' }, { msg: 'This is an error' }],
'many-%': ['replace%%%%s%%%%many%s%s%s', 'percent'],
'object-to-string': ['foo %s bar', { toString() { return 'bla'; } }],
'object-%s': ['foo %s bar', { a: true, b: false }],
};

const bench = common.createBenchmark(main, {
Expand Down
18 changes: 13 additions & 5 deletions benchmark/util/inspect-proxy.js
Original file line number Diff line number Diff line change
Expand Up @@ -3,13 +3,21 @@
const util = require('util');
const common = require('../common.js');

const bench = common.createBenchmark(main, { n: [2e4] });
const bench = common.createBenchmark(main, {
n: [1e5],
showProxy: [0, 1],
isProxy: [0, 1]
});

function main({ n }) {
const proxyA = new Proxy({}, { get: () => {} });
const proxyB = new Proxy(() => {}, {});
function main({ n, showProxy, isProxy }) {
let proxyA = {};
let proxyB = () => {};
if (isProxy) {
proxyA = new Proxy(proxyA, { get: () => {} });
proxyB = new Proxy(proxyB, {});
}
bench.start();
for (let i = 0; i < n; i += 1)
util.inspect({ a: proxyA, b: proxyB }, { showProxy: true });
util.inspect({ a: proxyA, b: proxyB }, { showProxy });
bench.end(n);
}
11 changes: 9 additions & 2 deletions lib/internal/util/inspect.js
Original file line number Diff line number Diff line change
Expand Up @@ -570,12 +570,12 @@ function formatValue(ctx, value, recurseTimes, typedArray) {
const context = value;
// Always check for proxies to prevent side effects and to prevent triggering
// any proxy handlers.
const proxy = getProxyDetails(value);
const proxy = getProxyDetails(value, !!ctx.showProxy);
if (proxy !== undefined) {
if (ctx.showProxy) {
return formatProxy(ctx, proxy, recurseTimes);
}
value = proxy[0];
value = proxy;
}

// Provide a hook for user-specified inspect functions.
Expand Down Expand Up @@ -1575,6 +1575,13 @@ function reduceToSingleString(
}

function hasBuiltInToString(value) {
// Prevent triggering proxy traps.
const getFullProxy = false;
const proxyTarget = getProxyDetails(value, getFullProxy);
if (proxyTarget !== undefined) {
value = proxyTarget;
}

// Count objects that have no `toString` function as built-in.
if (typeof value.toString !== 'function') {
return true;
Expand Down
20 changes: 14 additions & 6 deletions src/node_util.cc
Original file line number Diff line number Diff line change
Expand Up @@ -91,15 +91,23 @@ static void GetProxyDetails(const FunctionCallbackInfo<Value>& args) {
if (!args[0]->IsProxy())
return;

CHECK(args[1]->IsBoolean());

Local<Proxy> proxy = args[0].As<Proxy>();

Local<Value> ret[] = {
proxy->GetTarget(),
proxy->GetHandler()
};
if (args[1]->IsTrue()) {
Local<Value> ret[] = {
proxy->GetTarget(),
proxy->GetHandler()
};

args.GetReturnValue().Set(
Array::New(args.GetIsolate(), ret, arraysize(ret)));
args.GetReturnValue().Set(
Array::New(args.GetIsolate(), ret, arraysize(ret)));
} else {
Local<Value> ret = proxy->GetTarget();

args.GetReturnValue().Set(ret);
}
}

static void PreviewEntries(const FunctionCallbackInfo<Value>& args) {
Expand Down
4 changes: 3 additions & 1 deletion test/benchmark/test-benchmark-util.js
Original file line number Diff line number Diff line change
Expand Up @@ -14,5 +14,7 @@ runBenchmark('util',
'size=1',
'type=',
'len=1',
'version=native'],
'version=native',
'isProxy=1',
'showProxy=1'],
{ NODEJS_BENCHMARK_ZERO_ALLOWED: 1 });
10 changes: 8 additions & 2 deletions test/parallel/test-util-inspect-proxy.js
Original file line number Diff line number Diff line change
Expand Up @@ -41,12 +41,18 @@ proxyObj = new Proxy(target, handler);
// Inspecting the proxy should not actually walk it's properties
util.inspect(proxyObj, opts);

// Make sure inspecting object does not trigger any proxy traps.
util.format('%s', proxyObj);

// getProxyDetails is an internal method, not intended for public use.
// This is here to test that the internals are working correctly.
const details = processUtil.getProxyDetails(proxyObj);
let details = processUtil.getProxyDetails(proxyObj, true);
assert.strictEqual(target, details[0]);
assert.strictEqual(handler, details[1]);

details = processUtil.getProxyDetails(proxyObj, false);
assert.strictEqual(target, details);

assert.strictEqual(
util.inspect(proxyObj, opts),
'Proxy [\n' +
Expand Down Expand Up @@ -105,7 +111,7 @@ const expected6 = 'Proxy [\n' +
' ]\n' +
']';
assert.strictEqual(
util.inspect(proxy1, { showProxy: true, depth: null }),
util.inspect(proxy1, { showProxy: 1, depth: null }),
expected1);
assert.strictEqual(util.inspect(proxy2, opts), expected2);
assert.strictEqual(util.inspect(proxy3, opts), expected3);
Expand Down