lib: fix ERR_INVALID_ARG_TYPE with --enable-source-maps

[kimjune01]

When --enable-source-maps is enabled but no source map exists for the script (e.g. a plain .mjs file), getErrorSourceLocation() returned undefined. This caused getErrMessage() to return undefined, which made innerOk() pass [undefined] as the message tuple to innerFail(), hitting the ERR_INVALID_ARG_TYPE guard instead of throwing AssertionError.

Fix all code paths in getErrorSourceLocation() that returned bare undefined to fall back to the raw generated source line, matching the behavior when source maps are disabled entirely. Also add a guard for when V8 fails to provide a source line at all.

Includes tests for both .mjs and .cjs files under --enable-source-maps.

Fixes: #63169

[atlowChemi]

@kimjune01 I think the commit's module should be lib, not assert, as I don't think this changes assert specifically, that is mostly the symptom, not the actual issue, no?

[kimjune01]

Good point — the root cause is in the source map resolution path, not assert itself. I'll update the title.

[atlowChemi]

Good point — the root cause is in the source map resolution path, not assert itself. I'll update the title.

@kimjune01 please reword the commit as well 🙏🏽
Let me know if any help is needed

[kimjune01]

Done — reworded commit to lib: prefix.

[codecov]

Codecov Report

❌ Patch coverage is 33.33333% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.12%. Comparing base (d4d35c6) to head (da520ed).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/internal/errors/error_source.js	33.33%	6 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #63215   +/-   ##
=======================================
  Coverage   90.12%   90.12%           
=======================================
  Files         743      743           
  Lines      242415   242422    +7     
  Branches    45656    45653    -3     
=======================================
+ Hits       218476   218491   +15     
  Misses      15438    15438           
+ Partials     8501     8493    -8     

Files with missing lines	Coverage Δ
lib/internal/errors/error_source.js	82.55% <33.33%> (+0.73%)	⬆️

... and 32 files with indirect coverage changes

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[atlowChemi]

@kimjune01 the CI failures all seem related to the changes

[kimjune01]

Rebased onto current main and fixed the two lint failures:

• Dropped the non-ASCII em-dash from the comments (lint-js-and-md)
• Added the DCO Signed-off-by (lint-commit-message)

The earlier build failures looked unrelated to this lib/ change; should be clean on the fresh run.

[kimjune01]

Done. Moved both cases into test-node-output-sourcemaps.mjs as snapshot fixtures under source-map/output/ with a // Flags: --enable-source-maps directive; dropped the standalone test.

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/74431/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/75155/

[kimjune01]

Rebased onto main. Could someone run CI?

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/75166/