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 90.04%. Comparing base (bbf51ad) to head (bef74dd).
⚠️ Report is 160 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   90.03%   90.04%           
=======================================
  Files         713      713           
  Lines      224950   224957    +7     
  Branches    42532    42535    +3     
=======================================
+ Hits       202542   202553   +11     
- Misses      14175    14199   +24     
+ Partials     8233     8205   -28     

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

... and 47 files with indirect coverage changes

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[atlowChemi]

@kimjune01 the CI failures all seem related to the changes

[legendecas]

Can this test use a fixture like test/parallel/test-node-output-sourcemaps.mjs rather than generating source codes dynamically?

[kimjune01]

refactored.

[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.

[legendecas]

Would you mind follow the setups in test/parallel/test-node-output-sourcemaps.mjs? These two test cases can be added to the existing output test.