feat: autofix extensionless paths with its setting

[Zamiell]

Description

The autofixer for the import-x/extensions rule does not seem to work out of the box on v4.16.1.

Reproduction

Copy paste the following into a terminal. (I think that this is probably the simplest possible reproduction.)

mkdir test
cd test
npm init --yes
npm install --save-dev eslint @eslint/js typescript typescript-eslint eslint-plugin-import-x eslint-import-resolver-typescript
echo '// @ts-check

import eslint from "@eslint/js";
import tseslint from "typescript-eslint";
import { importX } from "eslint-plugin-import-x";

// Following the vanilla instructions from here:
// https://typescript-eslint.io/getting-started
export default tseslint.config(
  eslint.configs.recommended,
  tseslint.configs.recommended,

  // Following the vanilla instructions from here:
  // https://github.com/un-ts/eslint-plugin-import-x/tree/master?tab=readme-ov-file#as-a-standalone-eslint-plugin
  {
    plugins: {
      "import-x": importX,
    },
    languageOptions: {
      ecmaVersion: "latest",
      sourceType: "module",
    },
    rules: {
      "import-x/extensions": ["error", "ignorePackages", { fix: true }],
    },
  },
);' > eslint.config.mjs
mkdir src
echo 'export const foo = 123;' > src/foo.ts
echo 'import { foo } from "./foo";

console.log(foo);' > src/main.ts
npx eslint src/main.ts # Reports 1 error, as expected.
npx eslint src/main.ts --fix # Does not fix anything.

[JounQin]

Because it doesn't know which extension should be used, you need to specify for example js: 'always' to make it work. It just impossible to know which extension should be used without a config.

[Zamiell]

But if I specify fix: true, then I expect an error message, not to fail silently. I think it is a bug.

[JounQin]

While there is indeed a chance to fix it automatically: read import-x/extensions setting and try them one by one and get the exact same resolved output extension.

So maybe it should be considered as an enhanced.

Kind of like #395

[JounQin]

But if I specify fix: true, then I expect an error message, not to fail silently. I think it is a bug.

Indeed, do you want to work on it?

[Zamiell]

Sure, I can implement an error message. But I am not smart enough to do the resolution detection (like #395), so I leave that to you. :)

[JounQin]

That's fine, we should make sure

eslint-plugin-import-x/src/rules/extensions.ts

Line 375 in e50c5a6

replaceImportPath(source.raw, fixedImportPath),

the fixedImportPath is different before report as a fix.