feat: add ESLint integration

[johnsoncodehk]

Added @volar/eslint package to export createProcessor method. Processor is the interface for ESLint to handle virtual code conversion. Downstream tools should build a complete ESLint plugin by themselves.

Usage

Here we take Vue as an example.

• eslint-plugin-vue.js

const { createProcessor } = require('@volar/eslint');
const { createParsedCommandLine, createVueLanguagePlugin } = require('@vue/language-core');
const ts = require('typescript');

module.exports.create = create;

function create(tsconfig) {
    const commonLine = createParsedCommandLine(ts, ts.sys, tsconfig);
    const languagePlugin = createVueLanguagePlugin(
        ts,
        filename => filename,
        ts.sys.useCaseSensitiveFileNames,
        () => '',
        () => commonLine.fileNames,
        commonLine.options,
        commonLine.vueOptions,
    );
    return {
        processors: {
            vue: createProcessor([languagePlugin], ts.sys.useCaseSensitiveFileNames),
        },
    };
}

• eslint.config.js

const eslint = require('@eslint/js');
const tseslint = require('typescript-eslint');

module.exports = [
    eslint.configs.recommended,
    ...tseslint.configs.recommended,
    {
        plugins: {
            vue: require('./eslint-plugin-vue').create(__dirname + '/tsconfig.json')
        }
    },
    {
        files: ["**/*.vue"],
        processor: "vue/vue"
    },
};