swc feat(es/testing): Parse test code as a `Program` instead of a `Module`

Description: This PR addresses the issue described in #8713

BREAKING CHANGE: This will break existing unit tests that use fold_module/visit_module/visit_mut_module if the visitor is intended to work for both modules and scripts, instead of using fold_program/visit_program/visit_mut_program. This will also break existing unit tests if they're testing with input code that gets parsed as a script in parse_program if the visitor expects a module (they will need to update their test! calls to add module as the first argument, or use a function like apply_module_transform)

Related issue (if exists):

Closes #8713

Jul 16 '24 23:07 leafypout

Several swc tests rely on the parsed test code being a module due to their visitors, going to have to fix these. The good news is that this will fix any of these issues for people using parse_script. e.g. some of the simplifier tests fail on scripts but not on modules.

Jul 17 '24 00:07 leafypout

CodSpeed Performance Report

Merging #9264 will not alter performance

_{Comparing levi-nz:issue-8713 (df6db60) with main (8263da1)}

Summary

✅ 194 untouched benchmarks

Jul 17 '24 01:07 codspeed-hq[bot]

I will probably clean up the internal API a bit because I think it's a bit messy, but essentially how testing works now:

Current test implementations will continue to work, unless the visitor(s) being tested is implemented wrongly. Since parse_program is the default now and not parse_module, any visitors using visit_module instead of visit_program won't work if the parsed AST ends up being a script (because visit_module won't be called, only visit_script will). Visitors should use visit_program if they want to handle both modules and scripts.
Callers can force the test implementation to use parse_module or parse_script instead of parse_program by calling test!(module, ...) and test!(script, ...) respectively.
Some tests need to use test!(module, ...) as mentioned above, since their visitors depend on the code being a module. A good example are the fixture tests in swc_ecma_transforms_module.