source: imaps-frontend/node_modules/import-local/index.js

'use strict';
const path = require('path');
const {fileURLToPath} = require('url');
const resolveCwd = require('resolve-cwd');
const pkgDir = require('pkg-dir');

module.exports = filename => {
        const normalizedFilename = filename.startsWith('file://') ? fileURLToPath(filename) : filename;
        const globalDir = pkgDir.sync(path.dirname(normalizedFilename));
        const relativePath = path.relative(globalDir, normalizedFilename);
        const pkg = require(path.join(globalDir, 'package.json'));
        const localFile = resolveCwd.silent(path.join(pkg.name, relativePath));
        const localNodeModules = path.join(process.cwd(), 'node_modules');

        const filenameInLocalNodeModules = !path.relative(localNodeModules, normalizedFilename).startsWith('..') &&
                // On Windows, if `localNodeModules` and `normalizedFilename` are on different partitions, `path.relative()` returns the value of `normalizedFilename`, resulting in `filenameInLocalNodeModules` incorrectly becoming `true`.
                path.parse(localNodeModules).root === path.parse(normalizedFilename).root;

        // Use `path.relative()` to detect local package installation,
        // because __filename's case is inconsistent on Windows
        // Can use `===` when targeting Node.js 8
        // See https://github.com/nodejs/node/issues/6624
        return !filenameInLocalNodeModules && localFile && path.relative(localFile, normalizedFilename) !== '' && require(localFile);
};