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]

LGTM. Would like @mdjermanovic to review before merging.

[lumirlumir]

@mdjermanovic

Thank you for your thorough review!

I've resolved all the comments and added the test cases you suggested in #212 (comment) and other comments.

The bug you pointed out in #212 (comment) was caused by the following code:

this.text.slice(this.#lineStartIndices.at(-1), index + 1)

Since I used the slice method with index + 1, it led to the error you mentioned.

I've now fixed this in 842dfb8, so the error no longer occurs.

The other private lazy methods already use the approach I implemented in 842dfb8, so the bug was only present in the #ensureLineStartIndicesFromIndex(index) method.

[mdjermanovic]

LGTM, thanks! Leaving open for @nzakas to verify changes after his approval.

[lumirlumir]

ping @nzakas

[nzakas]

LGTM. Thanks!