One widely-used example is Angular. (It may have changed, I’m not entirely up-to-date.) The Angular Compatibility Compiler (ngcc) creates optimized code of Angu

One widely-used example is Angular. (It may have changed, I’m not entirely up-to-date.) The Angular Compatibility Compiler (ngcc) creates optimized code of Angular component libraries right next to the original files inside node_modules. It does this automatically as part of the Angular build process. That’s also how I would share any patches: Just apply them when needed during the build process. NPM doesn’t care about what changes inside packages, so you can hack them all you want.