Build output is different when building on Windows or Mac

[mabramishvili]

Rollup Version

2.70.1

Operating System (or Browser)

Windows

Node Version (if applicable)

14.16.1

Link To Reproduction

not available

Expected Behaviour

Seems like on Windows, preserveModulesRoot: 'src' will only work on entry files (files defined in "input"). While on OSX it will work on all files.

I would expect it to be consistent between different environments.

Found this question but there is no working answer:
https://stackoverflow.com/questions/64570174/rollup-preservemodulesroot-not-working-as-expected

Actual Behaviour

I have a build output defined like:

{
  input: 'src/index.ts',
  output: [
    {
      dir: 'dist/cjs',
      format: 'cjs',
      preserveModules: true,
      preserveModulesRoot: 'src',
      sourcemap: true,
      exports: 'named',
    },
    {
      dir: 'dist/esm',
      format: 'esm',
      preserveModules: true,
      sourcemap: true,
      preserveModulesRoot: 'src',
      exports: 'named',
    },
  ],
}

When building on Windows, the output in dist is like:

dist
    -- esm
        --components
        --src
            --components
       index.d.ts
       index.js

esm/components will only include d.ts files and esm/src/components will actually include .js files

When building on OSX, the output in dist is like:

dist
    -- esm
        --components
       index.d.ts
       index.js

notice there is no "src" folder and all files are placed inside esm/components.

[cleverpp]

+1， i have same problem。

after debugging, I found that it is caused by the following code

at 'rollup/src/utils/options/normalizeOutputOptions.ts'

...
preserveModulesRoot: getPreserveModulesRoot(config),
....

const getPreserveModulesRoot = (
	config: OutputOptions
): NormalizedOutputOptions['preserveModulesRoot'] => {
	const { preserveModulesRoot } = config;
	if (preserveModulesRoot === null || preserveModulesRoot === undefined) {
		return undefined;
	}
	return resolve(preserveModulesRoot);
};

but, at ''src/chunk.ts" 中

const currentPath = `${currentDir}/${fileName}`;
const { preserveModulesRoot } = options;
if (preserveModulesRoot && currentPath.startsWith(preserveModulesRoot)) {
	path = currentPath.slice(preserveModulesRoot.length).replace(/^[\\/]/, '');
} else {
	path = relative(preserveModulesRelativeDir, currentPath);
}

currentPath not resolve， but preserveModulesRoot had resolve， so in windows platform，currentPath.startsWith(preserveModulesRoot) always be false。

[Tanimodori]

+1 This bug leads to preserveModuleRoot not working. That startsWith is definitely the smoking gun. Until this pr get merged, my temp fix (see Tanimodori/generator-vite-electron-builder@ae8351a) is adding plugin to fix:

const config = {
  plugins: [
    {
      name: 'fixPreserveModulesRoot',
      renderStart(options) {
        options.preserveModulesRoot = options.preserveModulesRoot?.replace(
          new RegExp(/\\/, 'g'),
          '/',
        );
      },
    },
  ],
};