util.inspect: use the shared native validateObject / ERR_INVALID_ARG_TYPE

[dylan-conway]

Problem

• src/js/internal/util/inspect.js carried a private copy (about 140 lines) of Node's ERR_INVALID_ARG_TYPE message builder and its own validateObject. Only util.formatWithOptions, the util.inspect.defaultOptions and replDefaults setters, and util.stripVTControlCharacters used it. Every other module uses the native $ERR_INVALID_ARG_TYPE and internal/validators.
• The copy accepted functions. util.formatWithOptions(() => {}, "x") and util.inspect.defaultOptions = () => {} succeed in Bun. Node throws ERR_INVALID_ARG_TYPE for both.

Fix

• Delete the copy. inspect.js now throws $ERR_INVALID_ARG_TYPE and calls the shared validateObject.
• jsFunction_validateObject (src/jsc/bindings/NodeValidator.cpp) accepts Node's optional third argument, a bitmask of kValidateObjectAllowNullable, kValidateObjectAllowArray and kValidateObjectAllowFunction. internal/validators exports the constants. Without the argument the function behaves as before. formatWithOptions passes kValidateObjectAllowArray, as Node does.
• Codes and messages are the ones Node v26.3.0 prints. The notes list every case I compared.
• Verified: test/js/node/util/util.test.js. Two new tests (the public surface, and the three flags through exposedInternals, ported from the validateObject block of Node's test-validators.js) fail with the old src/ and pass with this diff. Also ran all of test/js/node/util/ and the vendored test-util*.js and test-repl-colors.js.

Background

• $ERR_INVALID_ARG_TYPE is an intrinsic of the builtin modules. The bundler rewrites it to the native error constructor in ErrorCode.cpp, so all modules print the same messages.
• internal/validators is the JS module that exposes the native validators in NodeValidator.cpp. validateObject is a $newCppFunction binding.
• Node's validateObject(value, name, options) takes the same bitmask (validators.js#L224-L270). The constants live in both validators.ts and NodeValidator.cpp and have to match. Both places now cite that source.

Notes

Messages compared with node v26.3.0 for formatWithOptions, the defaultOptions setter and stripVTControlCharacters with [], a function, null, undefined, 5, 'test', 5n, a symbol, a Date, a null prototype object and { depth: 3 }: identical in every case.

Differences from the deleted copy, all of which now match Node v26:

• functions are rejected by validateObject.
• a function without a name renders as Received function (the copy printed Received type function ([Function (anonymous)])).
• long bigints and symbols are no longer cut to 25 characters plus .... Node v26 does not cut them either. Strings are still cut.

The existing node-inspect-tests already assert the null, 'bad' and inspectOptions messages and still pass.

inspect.replDefaults: Bun defines this accessor eagerly in inspect.js. Node only defines it in the standalone REPL (kStandaloneREPL in repl.js), and that setter also calls validateObject(options, "options"). So the setter now rejects functions and arrays the same way the REPL setter does in Node and in Bun's repl.js.

Node's whole test/parallel/test-validators.js is not vendored here because its validateArray block fails on main for an unrelated reason: the minLength message renders the name as type string ('foo') (ErrorCode.cpp:1066) and uses the pre-v26 reason text. That is tracked separately.

Pre-existing and unchanged: determineSpecificType prints the inspected value for an object whose constructor property is falsy, where Node prints [Object].

Adoption changes on top of the original commit: removed the now unused ErrorCaptureStackTrace binding (oxlint failed on it), added the flags test, added the source citations, and made both tests assert the full messages.

util-inspect.test.js "no assertion failures 2" and the parse-args stress test exceed the 5 s timeout on my debug build with and without this diff (7 to 11 s, host load average about 40). Not related to this change.

[coderabbitai]

Walkthrough

Changes

The PR centralizes object validation in internal/validators, adds configurable validation flags, updates native validation behavior, and applies the shared validation logic to inspect utilities. Tests cover supported and rejected value types.

Object validation

Layer / File(s)	Summary
Validator flags and native behavior src/js/internal/validators.ts, src/jsc/bindings/NodeValidator.cpp	Adds bitmask constants for nullable values, arrays, and functions. The native validator applies these flags while continuing to reject unsupported values.
Inspect validator integration src/js/internal/util/inspect.js	Uses shared validators and errors. formatWithOptions allows arrays for inspectOptions.
Validation coverage test/js/node/util/util.test.js	Tests inspect utility validation and internal validateObject behavior for individual and combined flags.

Suggested reviewers: cirospaciari, robobun

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title clearly summarizes the main change: replacing private inspection validation with shared native validation.
Description check	✅ Passed	The description explains the change and verification steps, including tests run and compatibility details.

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[robobun]

^{Updated 3:38 AM PT - Aug 21st, 2026}

✅ @robobun, your commit f6b6f23a6c9978e74e9660cda5132dfadd499cbc passed in Build #102563! 🎉

---

🧪   To try this PR locally:

bunx bun-pr 39920

That installs a local version of the PR into your bun-39920 executable, so you can run:

bun-39920 --bun

[robobun]

Adopted at dylan-conway's request. Changes since the original commit:

• Removed the ErrorCaptureStackTrace binding in inspect.js that the deleted block was the last user of. The Lint JavaScript check failed on it.
• Added a test for all three kValidateObject* flags in test/js/node/util/util.test.js (the validateObject block of Node's test-validators.js, through exposedInternals). Only kValidateObjectAllowArray had coverage through the public API. Both new tests assert the full messages, checked against node v26.3.0.
• Cited the Node source for the flag values in validators.ts and NodeValidator.cpp.

Verification on a debug build: util.test.js passes (211 tests). Both new tests fail when the three src/ files are swapped back to main. The messages for every case I tried match node v26.3.0. The PR body has the details.

[coderabbitai]

Actionable comments posted: 5

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Inline comments:
In `@src/jsc/bindings/NodeValidator.cpp`:
- Around line 612-614: Move the object-validation bit values from
NodeValidator.cpp:612-614 into the shared header declaring V::validateObject,
documenting that internal/validators is their JS-visible mirror. In
src/js/internal/validators.ts:128-131, document the native definition as
authoritative and add the composite constants kValidateObjectAllowObjects and
kValidateObjectAllowObjectsAndNull for compatibility with ported Node code.
- Line 611: Update the options extraction in NodeValidator to use
JSValue::toInt32 with the current scope, preserving numeric bitmask values
including double-backed numbers; propagate coercion exceptions with
RETURN_IF_EXCEPTION(scope, {}) before using the resulting int32_t.

In `@test/js/node/util/util.test.js`:
- Around line 388-397: Strengthen the invalid-argument rejection assertions in
the formatWithOptions and util.inspect.defaultOptions tests to include the
complete expected message, not only ERR_INVALID_ARG_TYPE code and TypeError
name. Cover each relevant invalid input case, including functions, null, arrays,
and primitive values, matching the established message assertion style used by
stripVTControlCharacters.
- Line 408: Update the comment above the validateObject coverage to include the
relevant regression tracking issue URL, replacing the versioned Node test-path
reference; if this is compatibility coverage rather than a regression test,
remove the comment instead.
- Around line 421-424: Update the combined-mask case in the validateObject tests
to invoke validateObject separately with null, an array, and fn using
kValidateObjectAllowNullable | kValidateObjectAllowArray |
kValidateObjectAllowFunction, asserting that each call does not throw; retain
the existing individual allowance cases.

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Fix all unresolved CodeRabbit comments on this PR:

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📥 Commits

Reviewing files that changed from the base of the PR and between 4448a2e and 3e0c389.

📒 Files selected for processing (4)

• src/js/internal/util/inspect.js
• src/js/internal/validators.ts
• src/jsc/bindings/NodeValidator.cpp
• test/js/node/util/util.test.js

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[claude]

LGTM — deletes the private ERR_INVALID_ARG_TYPE / validateObject copy in inspect.js in favor of the shared native path, and extends jsFunction_validateObject with Node's optional flags bitmask.

What was reviewed:

• All ~90 existing two-arg validateObject callers across src/js/ — none pass a third argument, so options defaults to 0 and behavior is unchanged for them.
• jsFunction_validateObject: isInt32()/asInt32() on the internal-only third arg is appropriate (no user coercion); JSC::isArray is still guarded by RETURN_IF_EXCEPTION; the isNull/isCallable/isArray/isObject ordering matches Node's semantics for every flag combination.
• Confirmed no orphaned primordials remain in inspect.js after the deletion (each of SafeMap, RegExpPrototypeTest, ArrayPrototypePop, etc. still has live callers), and no stray codes.* references.
• The defaultOptions / replDefaults setters now reject functions and arrays like Node; new tests assert exact v26.3.0 messages and exercise every flag combination.

Extended reasoning...

Overview

This PR removes ~140 lines of duplicated ERR_INVALID_ARG_TYPE message-builder and a local validateObject from src/js/internal/util/inspect.js, replacing them with the shared $ERR_INVALID_ARG_TYPE intrinsic and require("internal/validators").validateObject. To support formatWithOptions (which allows arrays), jsFunction_validateObject in NodeValidator.cpp is extended to accept Node's optional third-argument bitmask (kValidateObjectAllowNullable | AllowArray | AllowFunction), and internal/validators.ts exports the four constants. Two new tests in test/js/node/util/util.test.js cover the public surface (formatWithOptions, inspect.defaultOptions, stripVTControlCharacters) and every flag combination via exposedInternals, with exact message strings verified against Node v26.3.0.

Security risks

None. This is argument validation for util.inspect-family APIs. The C++ change reads an internal int32 flag via isInt32() (no coercion, so no user-code execution) and otherwise uses the same JSC::isArray / isCallable / isObject checks as before, with the existing RETURN_IF_EXCEPTION after isArray. No new untrusted-input parsing, no auth/crypto/permission surface.

Level of scrutiny

Medium-low. It touches a native binding and a widely-used internal validator, but the change is strictly additive on the native side: with no third argument (every existing caller in src/js/ — I checked all ~90) options is 0 and the null/callable/array/object checks fire exactly as before. The JS-side change is a straight substitution of a duplicated helper for the canonical one, which is exactly the "one implementation, in the right place" pattern the review guide asks for. The behavioral change (rejecting functions for formatWithOptions / defaultOptions) is a Node-compat fix, verified against the reference binary.

Other factors

• My earlier note about the dead ErrorCaptureStackTrace primordial was addressed in 3e0c389; I confirmed no codes.* references remain and every other primordial the deleted block used still has live callers in the file.
• All CodeRabbit threads are resolved: reciprocal source citations were added for the mirrored constants, the flags test now exercises the combined mask with each allowed value kind, and each rejection asserts the full message. The isInt32() choice was explained (internal callers only pass the exported int32 constants) and accepted.
• Test coverage is thorough: exact error messages, both public entry points, all three flags individually, the combined mask, and per-kind rejection with the other two flags set. exposedInternals["internal/validators"] already exists in internal-for-testing.ts.
• The PR body documents the message differences from the deleted copy (functions, anonymous-function rendering, no 25-char truncation for bigints/symbols) and confirms they now match Node v26. The vendored test-util* and test-repl-colors suites were also run.