feat: add support for getLocFromIndex

[lumirlumir]

Prerequisites checklist

• I have read the contributing guidelines.

What is the purpose of this pull request?

Working in progress.

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Related Issues

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Prerequisite

• feat: add support for getLocFromIndex and getIndexFromLoc rewrite#212

[nzakas]

Before you get too far on this, is this function currently needed? As discussed in eslint/rewrite#166, this is an expensive operation and I don't think we want to incorporate it unless we absolutely need it.

[lumirlumir]

@nzakas

I thought this method could replace the findOffsets method used throughout the rules in @eslint/markdown, so I saw it as both a refactor and a new feature.

It’s currently used in two rules, and I use this kind of logic in my own rules as well (for context, please see https://github.com/lumirlumir/npm-eslint-plugin-mark/blob/main/packages/eslint-plugin-mark/src/core/ast/text-handler/text-handler.js).

If this feature isn’t necessary for now, I’ll go ahead and close it.

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(If it is fine, I would like to keep exploring and look for a more performant solution.)

[nzakas]

@lumirlumir ah, I forgot about that. Gotcha. 👍 If you're going to go through the trouble of investigating, then I'd suggest doing it on TextSourceCodeBase so every project can benefit.

[lumirlumir]

@nzakas Thanks for understanding!

I’ll keep this PR open for now, move on to implementing TextSourceCodeBase, and then come back to this one afterward.

Can I assign myself for the issue I've created? eslint/rewrite#166

[nzakas]

Go ahead.

[nzakas]

The other thing to keep in mind is that findOffsets() is not always used from the beginning of the document. Like in this case:

markdown/src/rules/no-html.js

Line 71 in cb5a956

const { lineOffset, columnOffset } = findOffsets(

It's finding the offset inside a given node's text.