load tsconfig compilerOptions, respects "extends" field

readCompilerOptions.js

const ts = require('typescript');
const { existsSync, readFileSync } = require('fs');
const { resolve, dirname } = require('path');

const readFile = (fname) => readFileSync(fname, 'utf8');
const normalizeSlashes = (value) => value.replace(/\\/g, '/');

module.exports = ({
    cwd = process.cwd(),
    project,
} = {}) => {
    let config = { compilerOptions: {} };
    let basePath = cwd;

    const configFileName = project
        ? resolve(cwd, project)
        : ts.findConfigFile(cwd, existsSync);

    if (configFileName) {
        const result = ts.readConfigFile(configFileName, readFile);

        if (result.error) {
            console.error('ERROR IN TYPESCRIPT while reading tsconfig');
            throw new Error(result.error)
        }

        config = result.config;
        basePath = normalizeSlashes(dirname(configFileName));
    }

    const result = ts.parseJsonConfigFileContent(
        config,
        ts.sys,
        basePath,
        undefined,
        configFileName
    );

    if (result.errors.length) {
        console.error('ERROR IN TYPESCRIPT while parsing tsconfig');
        throw new Error(result.errors[0]);
    }

    return result.options;
};