Use Asynchronous Code for Loading Modules

[leeyi45]

This PR is mainly aimed at addressing #1348 . I have only been able to write an async implementation for the transpiler and stepper. Both the interpreter and ec-evaluator will need further work and discussion for such implementations.

This PR also incorporates the changes from #1470 .

[coveralls]

Pull Request Test Coverage Report for Build 5936042370

• 215 of 269 (79.93%) changed or added relevant lines in 23 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.1%) to 83.014%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/modules/moduleLoader.ts	3	5	60.0%
src/transpiler/transpiler.ts	42	44	95.45%
src/runner/sourceRunner.ts	8	11	72.73%
src/interpreter/interpreter.ts	2	6	33.33%
src/utils/arrayMap.ts	17	21	80.95%
src/utils/assert.ts	4	9	44.44%
src/modules/errors.ts	8	16	50.0%
src/modules/moduleLoaderAsync.ts	43	52	82.69%
src/stepper/stepper.ts	11	28	39.29%

Files with Coverage Reduction	New Missed Lines	%
src/interpreter/interpreter.ts	1	89.9%

Totals
Change from base Build 5838197500:	0.1%
Covered Lines:	10838
Relevant Lines:	12635

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💛 - Coveralls

[martin-henz]

This PR is mainly aimed at addressing #1348 . I have only been able to write an async implementation for the transpiler and stepper. Both the interpreter and ec-evaluator will need further work and discussion for such implementations.

This PR also incorporates the changes from #1470 .

I think the interpreter in src/interpreter/interpreter.ts is no longer in use, see #1348

So what would remain to be refactored is the module loading of ec-evaluator.

Note that src/interpreter/interpreter-non-det.ts does not handle modules. So that would be a nice CP3108 project.

[Yongbeom-Kim]

LGTM... but I'm not sure if I'm familiar enough with the js-slang repo that I didn't miss anything

[leeyi45]

I'll do another once over myself, but if all's good I'll do the merge