feat: add assert/is-well-formed-string

[gunjjoshi]

This commit adds the assert/is-well-formed-string module for checking well-formed-strings.

Resolves #1065

Description

Added the is-well-formed-string package. It checks for four things to check if a string is well formed or not:

1. A low surrogate is present at the beginning.
2. A high surrogate is present at the last.
3. No low surrogate after a high surrogate.
4. No high surrogate before a low surrogate.

What is the purpose of this pull request?

This pull request:

• Adds a package to check if a string is well-formed or not.

Related Issues

Does this pull request have any related issues?

This pull request:

• resolves [RFC]: add @stdlib/assert/is-well-formed-string #1065

Questions

Any questions for reviewers of this pull request?

No.

Other

Any other information relevant to this pull request? This may include screenshots, references, and/or implementation notes.

Screenshot of tests:

Checklist

Please ensure the following tasks are completed before submitting this pull request.

• ☑️ Read, understood, and followed the contributing guidelines.

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@stdlib-js/reviewers

[Planeshifter]

Thanks for working on this! Looks very good; left some comments that will need to be addressed before merging.

[Planeshifter]

We should not initialize the i variable outside the function scope. Just declare var i; in L45 before the loop.

[gunjjoshi]

I assumed that all variables should be declared in the variables section.
But yes, it is outside the scope of the function, and we should avoid using global variables.
I've made the suggested change.

[gunjjoshi]

@Planeshifter
There is some error in linting the examples. I have written the correct outputs, but it is expecting something else, and thus giving errors. I checked the implementation of the functions, it is indeed correct.

[Planeshifter]

@gunjjoshi Thanks for checking! I believe the issue is that the instanceof String check doesn't work across realms when there are multiple String constructors. To lint examples and their expected outputs, we spawn a separate process via vm2 that will have it's own String constructor. Here is how we make the object check in the assert/is-string package https://github.com/stdlib-js/stdlib/blob/develop/lib/node_modules/%40stdlib/assert/is-string/lib/object.js more robust to have it work across realms.
Would you mind updating this package accordingly?

[gunjjoshi]

@gunjjoshi Thanks for checking! I believe the issue is that the instanceof String check doesn't work across realms when there are multiple String constructors. To lint examples and their expected outputs, we spawn a separate process via vm2 that will have it's own String constructor. Here is how we make the object check in the assert/is-string package https://github.com/stdlib-js/stdlib/blob/develop/lib/node_modules/%40stdlib/assert/is-string/lib/object.js more robust to have it work across realms. Would you mind updating this package accordingly?

Sure, I'll update this package.

[gunjjoshi]

Great ! It got passed by the CI pipeline.
So the string object checking was creating the problem.

[Planeshifter]

@gunjjoshi Will merge after CI clears; thanks again for your contribution!