fix: show both require() and import() errors when module loading fails

[guoyangzhen]

Summary

Fixes #5235 (related to #5792 - edited by @mark-wiemer)

When requireModule() falls back to import() after require() fails, and both methods fail, the current heuristics often select the less helpful error to display. This is especially problematic with ts-node + CommonJS setups on Node.js 22+.

Changes

Instead of guessing which error is more relevant, this PR shows both errors with clear labels when neither matches the known special cases (#5393, #5411). This lets users see the full picture and diagnose the actual root cause.

Example output

Before: only shows the generic import error (e.g., ERR_MODULE_NOT_FOUND)

After:

Failed to load file via both require() and import().

[require() error]:
Cannot find module './test/something.test.ts' ...

[import() error]:
ERR_MODULE_NOT_FOUND ...

Context

• Existing special cases for TypeScript files (🐛 Bug: original require() errors are masked with an unrelated ERR_UNKNOWN_FILE_EXTENSION #5393) and exports mismatches (🐛 Bug: Unhelpful error message when a default import is made from a module without a default export #5411) are preserved
• The new ERR_MOCHA_MODULE_LOAD_FAILED error code makes it easy to identify combined errors
• Both original errors are available via error.cause for programmatic access

[linux-foundation-easycla]

• ✅ login: mark-wiemer / name: Mark Wiemer (2195735)
• ❌ - login: @guoyangzhen / name: guoyangzhen . The commit (83aac47, b10432e, c8ec45f) is not authorized under a signed CLA. Please click here to be authorized. For further assistance with EasyCLA, please submit a support request ticket.

[github-actions]

👋 Hi @guoyangzhen, thanks for the pull request! A scan flagged a concern with it. Could you please take a look?

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[mark-wiemer]

@mochajs/maintenance-crew I like this idea, what are your thoughts?

[JoshuaKGoldberg]

Ah, this old idea again. I'll post the old context in #5792 to keep discussion in the issue-side.

[mark-wiemer]

@guoyangzhen unit tests for this change will be required before we merge :) we are discussing the core of this in #5792 currently and may move the convo to #5235 soon

[guoyangzhen]

Hi @mark-wiemer, I've added unit tests as requested. The test creates a fixture that fails on require() with a custom error, stubs doImport to also fail, and verifies the combined error (ERR_MOCHA_MODULE_LOAD_FAILED) is thrown with both error messages included. Commits: fixture (c8ec45f) and test (b10432e).

[guoyangzhen]

@mark-wiemer I've signed the EasyCLA — could you please re-trigger the check? Also, I noticed the CLA seems to need re-signing for each new PR. Thanks!

[mark-wiemer]

/easycla

[mark-wiemer]

Thanks, we have had some issues with EasyCLA recently, we are working on them in private comms :)

[mark-wiemer]

@lukaszgryglicki can you check this one out? See also #5803