feat: add support for getLocFromIndex and getIndexFromLoc

[lumirlumir]

Prerequisites checklist

• I have read the contributing guidelines.

What is the purpose of this pull request?

Hello,

In this PR, I've completed implemention of getLocFromIndex() and getIndexFromLoc().

I based the implementation on the current JavaScript SourceCode class and incorporated the fast lookup algorithm discussed in eslint/eslint#19782.

The logic of getLocFromIndex() and getIndexFromLoc() is nearly identical to that in the JavaScript SourceCode class, with the key difference being that it accounts for the lineStart and columnStart values initialized in the constructor.

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lineStart and columnStart

TextSourceCodeBase should accept lineStart and columnStart, as these can vary depending on the language, and both getLocFromIndex() and getIndexFromLoc() rely on them for accurate calculations. Here are some examples:

• https://github.com/eslint/css/blob/main/src/languages/css-language.js#L69-L79
• https://github.com/eslint/markdown/blob/main/src/language/markdown-language.js#L91-L101
• https://github.com/eslint/json/blob/main/src/languages/json-language.js#L44-L54
• https://github.com/yeonjuan/html-eslint/blob/main/packages/eslint-plugin/lib/languages/html-language.js#L21-L31

What changes did you make? (Give an overview)

I've completed implemention of getLocFromIndex() and getIndexFromLoc().

Related Issues

fixes: #166
refs: eslint/markdown#376, eslint/css#167, eslint/json#109, eslint/eslint#19782

Is there anything you'd like reviewers to focus on?

Prerequisites

• perf: improve time complexity of getLocFromIndex eslint#19782

[nzakas]

I think we should do this lazily. It doesn't make sense to go through this process until we know someone needs this information.

[nzakas]

Thanks for taking a look at this. I left some comments throughout.

Overall, I'd like to think more about how to lazily generate the data needed. For instance, if someone calls getLocFromIndex(5), we should only generate the line endings up to index 5. If someone then calls getLocFromIndex(22), we can go on to generate line endings up to index 22.

That way, we're saving calculations until we really need them.