Webpack: Trigger a file watch recompile on an unchanged file

Question

I'm developing a Webpack 5 plugin and I need to manually trigger a recompile on a watched file without modifying it (mainly to do some niche HMR stuff).

I figure the easiest way is to convince the compiler that the file has changed. I don't want to actually change the file with fs. I've looked into the webpack source code - spoofing webpack's NodeWatchFileSystem looks to be very hacky. Triggering a recompile another way is beyond me.

Answer 1

Tracing backwards all the way to the file watchers, when a file is saved, the file watcher emits the "change" event and the functions that follow consume this event and trigger the recompilation for the changed file.

As we require a "change" event and a recompilation, but for an unchanged file, accessing these consumer functions (setFileTime(...)) & simulating the consumption of a "change" event would be a cleaner solution like below, worked great for me!

//unchanged file that needs to be recompiled
let filePath = "/Users/my-project/src/HelloWorld.js" 

// Webpack v5.x
compiler.watchFileSystem.watcher.fileWatchers
  .get(filePath)
  .directoryWatcher.setFileTime(
    filePath,
    new Date().getTime(),
    false,
    false,
    "change"
  );

// Webpack v4.x
compiler.watchFileSystem.watcher.fileWatchers
  .find((watcher) => watcher.path === filePath)
  .directoryWatcher.setFileTime(
    filePath,
    new Date().getTime(),
    false,
    "change"
  );