feat(helpers): allow calling functions in fake placeholders

[hiSandog]

Summary

• bind methods resolved from objects and primitive values in helpers.fake evaluation
• allow chained instance property/method access after faker function references and calls
• add regression coverage for primitive length, string method, and Date method chains

Fixes #3465.

Validation

• pnpm vitest run test/modules/helpers.spec.ts --testNamePattern "fake"
• pnpm exec tsc --noEmit
• pnpm exec prettier --check src/modules/helpers/eval.ts test/modules/helpers.spec.ts
• pnpm exec eslint src/modules/helpers/eval.ts test/modules/helpers.spec.ts
• git diff --check

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[codecov]

Codecov Report

❌ Patch coverage is 90.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 98.87%. Comparing base (f433771) to head (a40cb4a).
⚠️ Report is 11 commits behind head on next.

Files with missing lines	Patch %	Lines
src/modules/helpers/eval.ts	90.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             next    #3841      +/-   ##
==========================================
- Coverage   98.90%   98.87%   -0.03%     
==========================================
  Files         899      900       +1     
  Lines        3113     3122       +9     
  Branches      574      578       +4     
==========================================
+ Hits         3079     3087       +8     
- Misses         30       31       +1     
  Partials        4        4              

Files with missing lines	Coverage Δ
src/modules/helpers/index.ts	95.27% <ø> (ø)
src/modules/helpers/eval.ts	94.80% <90.00%> (-0.85%)	⬇️

... and 2 files with indirect coverage changes

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[ST-DDT]

Can you please restrict access to constructor, prototype and similar special properties?

[ST-DDT]

And don't forget to adjust the JSDocs +examples on faker.helpers.fake.

[hiSandog]

Thanks for the review. I pushed a follow-up in a40cb4a that blocks constructor, prototype, and __proto__ from fake expression resolution, with coverage in both fakeEval and faker.helpers.fake tests. I also updated the faker.helpers.fake JSDoc examples to cover chained property resolution.

[ST-DDT]

Please also remove/update this hint.

• It is also NOT possible to use any non-faker methods or plain javascript in such patterns.

[ST-DDT]

Please also add an example with a function call. e.g. date.toISOString()

[ST-DDT]

IMO this should throw. Because these should never be accessible.

[ST-DDT]

@faker-js/maintainers Any suggestion for improving the PR title to better express the change?

[Shinigami92]

@faker-js/maintainers Any suggestion for improving the PR title to better express the change?

Think it is fine now