Modifies context of imports. Should be called before whatever compiles the imports

context-loader.js

const fs = require('fs');

const requirePatterns = [
  /(import.*from\W*)(?:(')(.*)(?!\/)'|(")(.*)(?!\/)")(.*)/g,
  /(require\W*\()(?:(')(.*)(?!\/)'|(")(.*)(?!\/)")(.*)/g
];
const extension = '.ts';

function decodeOption(key, value) {
  switch (key) {
    case 'preserve-depth': return value === 'true';
    default: return value;
  }
}

function parseOptions(query) {
  query = query.substring(1).split('&');
  const options = {
    paths: query[0].split(':').map(function(e) {
      return e.replace(/\/$/, '')
    })
  };

  for (var i = 0; i < query.length; i++) {
    var obj = query[i].split('=');
    options[obj[0]] = decodeOption(obj[0], obj[1]);
  }

  return options;
}

function isScopePresent(scope, path) {
  return !!~path.indexOf(scope);
}

function escapeToRoot(path) {
  return '../'.repeat(path.split('/').length);
}

function splitPathOnPattern(path, pathPattern) {
  return new RegExp('(.*)(' + pathPattern + ')((?:(?!'+ pathPattern +').)*)').exec(path);
}

function isImportValid(path) {
  try {
    fs.statSync(path);
    return true;
  } catch (e) {
    return false;
  }
}

function generateRequirePattern() {
  return new RegExp(requirePatterns.map(r => r.source).join('|'), 'g');
}

module.exports = function(content) {
  this.cacheable();

  const options = parseOptions(this.query);
  const paths = options.paths;
  const preserveDepth = options['preserve-depth'];

  var context = this.context;

  if (isScopePresent(paths[0], context)) {

    var pathRequirePattern = generateRequirePattern();
    var contextPathParts = splitPathOnPattern(context, paths[0]);

    var relativeResourcePath = contextPathParts[2] + contextPathParts[3];
    var newResourcePathPrefix = escapeToRoot(relativeResourcePath) + paths[1];
    var absoluteResourceDirPath = contextPathParts[1] + paths[1];

    var resourcePath = (preserveDepth ? contextPathParts[3] : '') + '/';
    newResourcePathPrefix += resourcePath;
    absoluteResourceDirPath += resourcePath;

    var imports;
    while ((imports = pathRequirePattern.exec(content)) != null) {
      var quotes = imports[2] || imports[4];
      var importResource = imports[3] || imports[5];

      var absoluteImportPath = absoluteResourceDirPath + importResource + extension;
      if (isImportValid(absoluteImportPath)) {
        var newImportPath = imports[1] + quotes + newResourcePathPrefix + importResource + quotes + imports[6];
        content = content.slice(0, imports.index) + newImportPath + content.slice(imports.index + imports[0].length);
      }
    }
  }
  return content;
};