[GeoffreyBooth]

This should presumably land after the next amaro version bump on main. The bundled deps/amaro/dist/register-strip.mjs and register-transform.mjs still call module.register(). This PR should land after amaro is updated to a release that includes nodejs/amaro#497 (module.registerHooks).

Removes module.register() (DEP0205), the --experimental-loader and --loader flags, and the machinery that supported them: the loader hooks worker thread, the hooks proxy, the async module customization hook chains for resolving and loading, the internal worker class used to run the loader thread, and the asynchronous module job linking. Module customization is now provided only by module.registerHooks(), which runs synchronously on the thread that loads the modules.

• The ES module loader always loads and links modules synchronously; the promise handling and the re-invented require() for imported CommonJS are gone. import() still defers evaluation to a later microtask.
• worker_threads.isInternalThread is kept and always false; removing it is left for a semver-major change.
• DEP0205 stays in deprecations.md as End-of-Life. ERR_ASYNC_LOADER_REQUEST_NEVER_SETTLED and ERR_LOADER_CHAIN_INCOMPLETE move to Legacy in errors.md.
• Tests that only exercised the async hooks are removed; new tests cover require() after a failed import() and that import() does not evaluate the module before returning.
• REPLACEME placeholders for the version are left for landing.

[nodejs-github-bot]

Review requested:

• @nodejs/config
• @nodejs/loaders
• @nodejs/test_runner
• @nodejs/userland-migrations

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/78704/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/78706/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/78722/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/78723/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/78724/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/78725/

[codecov]

Codecov Report

❌ Patch coverage is 98.54015% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.65%. Comparing base (d699704) to head (a825144).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/node_watchdog.cc	0.00%	0 Missing and 1 partial ⚠️
src/node_worker.cc	75.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #67090      +/-   ##
==========================================
- Coverage   90.67%   90.65%   -0.02%     
==========================================
  Files         797      794       -3     
  Lines      278791   276730    -2061     
  Branches    53617    53319     -298     
==========================================
- Hits       252794   250878    -1916     
+ Misses      16356    16203     -153     
- Partials     9641     9649       +8     

Files with missing lines	Coverage Δ
lib/internal/bench_runner/cli.js	94.15% <ø> (-0.01%)	⬇️
lib/internal/errors.js	98.80% <100.00%> (-0.01%)	⬇️
lib/internal/main/eval_string.js	79.48% <100.00%> (ø)
lib/internal/main/worker_thread.js	94.87% <100.00%> (-0.24%)	⬇️
lib/internal/modules/customization_hooks.js	100.00% <100.00%> (ø)
lib/internal/modules/esm/load.js	95.54% <100.00%> (-1.27%)	⬇️
lib/internal/modules/esm/loader.js	99.56% <100.00%> (-0.35%)	⬇️
lib/internal/modules/esm/module_job.js	100.00% <100.00%> (+0.41%)	⬆️
lib/internal/modules/esm/module_map.js	98.48% <100.00%> (+0.01%)	⬆️
lib/internal/modules/esm/translators.js	97.42% <100.00%> (-0.21%)	⬇️
... and 14 more

... and 33 files with indirect coverage changes

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