NativeScript/packages/webpack/host/resolver.ts

import { parse, join } from 'path';
import { statSync } from 'fs';

export function getResolver(platforms: string[], explicitResolve?: string[], nsPackageFilters?: string[], platformSpecificExt?: string[]) {
	explicitResolve = explicitResolve || [];
	nsPackageFilters = nsPackageFilters || ['nativescript', 'tns', 'ns', '@nativescript'];
	platformSpecificExt = platformSpecificExt || ['.ts', '.js', '.scss', '.less', '.css', '.html', '.xml', '.vue', '.json'];

	return function (path: string) {
		const nmIndex = path.lastIndexOf('node_modules');

		if (nmIndex !== -1) {
			const subPath = path.substr(nmIndex + 'node_modules'.length).replace(/\\/g, '/');
			const shouldResolve = explicitResolve.length && explicitResolve.some((packageName) => subPath.indexOf(packageName) !== -1);
			const pathParts = subPath.split(/[/\-_]/);

			if (!shouldResolve && pathParts.every((p) => nsPackageFilters.every((f) => f !== p))) {
				return path;
			}
		}

		const { dir, name, ext } = parse(path);

		if (platformSpecificExt.indexOf(ext) === -1) {
			return path;
		}

		for (const platform of platforms) {
			const platformFileName = `${name}.${platform}${ext}`;
			const platformPath = toSystemPath(join(dir, platformFileName));

			try {
				if (statSync(platformPath)) {
					return platformPath;
				}
			} catch (_e) {
				// continue checking the other platforms
			}
		}

		return path;
	};
}

// Convert paths from \c\some\path to c:\some\path
function toSystemPath(path: string) {
	if (!process.platform.startsWith('win32')) {
		return path;
	}

	const drive = path.match(/^\\(\w)\\(.*)$/);
	return drive ? `${drive[1]}:\\${drive[2]}` : path;
}