Traverses .ts source files in a project and replaces all absolute imports with aliases to relative ones, according to paths in tsconfig.json

replaceAbsoluteImports.js

const fs = require("fs");
const path = require("path");
const globby = require("globby");

const srcPath = fn("../src");
const aliases = getAliases();

(async () => {
  const files = await findFiles();
  files
    .forEach(async (fn, i) => {
      console.debug(i, "[processing]", fn);
      const fullFn = path.join(srcPath, fn);
      let text = fs.readFileSync(fullFn, "utf8");
      text = await replaceAliases(text, fn);
      fs.writeFileSync(fullFn, text, { encoding: "utf8" });
    });
})();

// console.log(aliases);

const catchImportFrom = /\sfrom\s+\'(\.[a-z]+\/?)([^']+)?\';/g;

async function replaceAliases(text, fn) {
  const fullFn = path.join(srcPath, fn);

  return text.replace(
    catchImportFrom,
    (match, alias, rest) => {
      // console.log(match, alias, rest);
      const target = aliases[alias];
      if (!target) {
        return match;
      }

      const abs = path.join(target, rest || "");
      let rel = path
        .relative(
          path.dirname(fullFn),
          abs
        )
        .replace(/\\/g, "/");
      if (!rel.startsWith(".")) {
        rel = `./${rel}`;
      }
      return ` from '${rel}';`;
    }
  );
}

async function findFiles() {
  const tsFiles = await globby(
    ["**/?(*.){js,jsx,mjs,ts,tsx}", "!**/*.d.ts"],
    { cwd: srcPath }
  );

  // tsFiles.forEach((f, i) => console.log(i, f))

  return tsFiles;
  // .map(fn => path.join(srcPath, fn))
  //   .slice(108, 109);
}

function fn(target) {
  return path.resolve(__dirname, target);
}

// fs.readFileSync
function getAliases() {
  const tsconfig = require(fn("../tsconfig.json"));
  const { paths } = tsconfig.compilerOptions;
  return Object.keys(paths)
    .reduce(
      (acc, k) => {
        const starts = k.endsWith("*") ? k.slice(0, -1) : k;
        const path0 = paths[k][0];
        const target = path.resolve(
          srcPath,
          path0.endsWith("*") ? path0.slice(0, -1) : path0
        );
        acc[starts] = target;
        return acc;
      },
      {}
    );
}