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util: inspect without showProxy triggers traps in proxified proxies #61061
Description
Version
v26.0.0-pre
Platform
Linux tumba 6.17.9-gentoo-yuran #1 SMP Thu Nov 27 04:38:45 +08 2025 x86_64 Intel(R) Core(TM)2 Quad CPU Q8200 @ 2.33GHz GenuineIntel GNU/Linux
Subsystem
util
What steps will reproduce the bug?
import { inspect } from "node:util";
const proxy = new Proxy({}, { get(...cause) { throw new EvalError('boom', { cause }); } });
const proxy2 = new Proxy(proxy, {});
console.log('proxy showProxy=true', inspect(proxy, { showProxy: true }));
console.log('nested showProxy=true', inspect(proxy2, { showProxy: true }));
console.log('proxy showProxy=false', inspect(proxy, { showProxy: false }));
console.log('nested showProxy=false', inspect(proxy2, { showProxy: false }));How often does it reproduce? Is there a required condition?
Always
What is the expected behavior? Why is that the expected behavior?
proxy showProxy=true Proxy [ {}, { get: [Function: get] } ]
nested showProxy=true Proxy [ Proxy [ {}, { get: [Function: get] } ], {} ]
proxy showProxy=false {}
nested showProxy=false {}{} could be something more meaningful (#60964 related) instead.
What do you see instead?
proxy showProxy=true Proxy [ {}, { get: [Function: get] } ]
nested showProxy=true Proxy [ Proxy [ {}, { get: [Function: get] } ], {} ]
proxy showProxy=false {}
file:///home/LiviaMedeiros/node/issue.mjs:3
const proxy = new Proxy({}, { get(...cause) { throw new EvalError('boom', { cause }); } });
^
EvalError: boom
at Object.get (file:///home/LiviaMedeiros/node/issue.mjs:3:53)
at formatValue (node:internal/util/inspect:1125:32)
at inspect (node:internal/util/inspect:409:10)
at file:///home/LiviaMedeiros/node/issue.mjs:9:39
at ModuleJob.run (node:internal/modules/esm/module_job:430:25)
at async onImport.tracePromise.__proto__ (node:internal/modules/esm/loader:654:26)
at async asyncRunEntryPointWithESMLoader (node:internal/modules/run_main:101:5) {
[cause]: [ {}, '0', {} ]
}
Node.js v26.0.0-preAdditional information
Not setting showProxy explicitly gives same result as with false.
The get trap is triggered (assuming the error is caught) for '0', then Symbol(nodejs.util.inspect.custom), then Symbol(Symbol.toStringTag) properties.
Activity
azadgupta1 commentedon Dec 15, 2025
I traced this through
util.inspect()and noticed that the failure happensinside
formatValue(), beforeformatRaw()is reached.When
showProxyis disabled, the inspected value can stop being treated as aProxy and later code ends up touching it in a way that triggers traps for nested
proxies.
I’m working on a small change to keep proxies opaque in this case and adding a
regression test. I’ll open a PR once it’s ready.
benjamingr commentedon Dec 15, 2025
Isn't this kind of counter to #60964 ?
LiviaMedeiros commentedon Dec 15, 2025
IIUC the consensus in #60964 is that
inspectshould mark proxies but still not trigger traps.If #61029 lands, the expected outputs here would be
Proxy({})andProxy(Proxy({})). The semverity must be kept in mind.If #60964 gets fixed in more extreme way, making inspecting first proxy throw, it would be aligned with nested proxy and this issue would be technically resolved as works-as-intended.
BridgeAR commentedon Dec 15, 2025
Good catch @LiviaMedeiros. I agree about the proxy needing to be unwrapped.
util: fix nested proxy inspection