[CodingRule]

reconstructErrorStack() takes the first stack frame as the require() caller. When a module.require tracing subscriber exists, that frame is TracingChannel.traceSync, so the arrow points at a nonexistent line of the parent file:

test.cjs:568
undefined
                     ^

Pick the first frame that belongs to the parent file instead. Works for nested callers too (the first parent frame is the require() call site).

Adds a test case with a tracing:module.require:start subscriber; it fails on current main and passes with this change.

Fixes: #55350

AI disclosure

This change was made with help from an AI coding assistant (Claude Mythos 5.1). I reviewed the diff and the reasoning behind it myself.

What was verified:

• Reproduced the bug on the current nightly (v27.0.0-nightly20261020) with a tracing:module.require:start subscriber: the arrow points at test.cjs:568 with undefined.
• Ran reconstructErrorStack() from both the original and patched loader.js against real stacks captured from the nightly, in four shapes: plain, with subscriber, nested callers, nested with subscriber. The patched version annotates the require() call site in all four. The original fails in both subscriber cases.
• The new test case fails on the unfixed nightly and the two existing cases still pass.
• tools/eslint on both files with --max-warnings=0.
• Built this branch on Windows (VS 2022 + ClangCL, vcbuild x64 release openssl-no-asm): test/es-module/test-cjs-esm-warn.js passes 3/3 on the built binary.
• Full suite (tools/test.py, 7281 tests): 56 failures, 55 of which fail identically on an unmodified nightly on the same machine (Windows symlink privilege, child_process shell, TLS CA, fs symlink/cp). The other, test-http-outgoing-end-cork, timed out under load and passes 10/10 in isolation on both binaries.

I'll follow up on review feedback myself.

[nodejs-github-bot]

Review requested:

• @nodejs/loaders

[github-actions]

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[MikeMcC399]

Not run locally: the test against a binary built from this branch (no ClangCL toolchain on my machine). I'll follow up on review feedback myself.

The Pull requests > Step 6: Test say:

Before submitting your changes in a pull request, always run the full Node.js test suite.

This is only possible if you have a local environment set up according to Building Node.js on supported platforms.

[CodingRule]

@MikeMcC399 thanks for pointing that out. I've since set up the Windows toolchain (VS 2022 + ClangCL) and run it locally on a build from this branch:

• test/es-module/test-cjs-esm-warn.js: 3/3 pass, including the new case.
• Full suite via tools/test.py (7281 tests): 56 failures. 55 of them fail identically on an unmodified nightly (v27.0.0-nightly20261020) on the same machine; they're Windows environment issues here (symlink privilege, child_process shell, TLS CA options, fs symlink/cp). The remaining one, test-http-outgoing-end-cork, was a request timeout under load and passes 10/10 in isolation on both binaries.

Updated the PR description accordingly.

[MikeMcC399]

https://github.com/nodejs/node/blob/main/BUILDING.md#building-nodejs-2

Tip

On Windows, creating symlinks requires Developer Mode to be enabled or running the command as Administrator. Tests that rely on creating symlinks may fail with EPERM errors if symlink creation is not permitted.