Avoid using unique ID in child compiler template

[helloitsjoe]

What problem does this solve?

Unique child compiler IDs cause a memory leak in watch mode

Resolves #1835

Details

This change reverts aa64b82, which introduced a change where each child compiler is given a unique ID. This causes duplicate source strings to be cached on every recompile, without removing the old sources.

More details and screenshots in the issue linked above. The main thing I'm unclear about is why unique IDs were used in the first place, but as far as I can tell the ID isn't referenced anywhere else. Let me know if I've missed something!

Testing done

• Unit tests pass
• Tested locally, the memory leak is resolved when using template instead of the unique ID

[alexander-akait]

Thank you

[creage]

@alexander-akait @helloitsjoe this change leads to an issue - webpack-dev-server doesn't pick changes:

[webpack-dev-server] App updated. Recompiling...
[webpack-dev-server] Nothing changed

Rolling back to html-webpack-plugin version 5.5.3 fixes the issue.

[alexander-akait]

@creage Can you create reproducible test repo?

[creage]

@alexander-akait here you go https://github.com/creage/html-webpack-plugin-nothing-changed

[alexander-akait]

@creage Thank you, I will look soon

[helloitsjoe]

@creage I cloned your reproduction repo and it looks like 5.5.4 also has the problem you describe. This change was released in 5.6.0, so it seems likely this is caused by something between 5.5.3 and 5.5.4, unless you're seeing something different.

[alexander-akait]

@creage Intresting, I would say that we have fixed the bug, before you always had extra compilation and spent extra resources and that is why you have reloading, but when you watch dll, dll-user doesn't really know should be the application reloaded or not, you don't have HMR and you don't watch, and so you have:

[webpack-dev-server] App updated. Recompiling...
[webpack-dev-server] Nothing changed.

Because webpack doesn't know how to apply changes. How to fix it:

watchFiles: [path.join(__dirname, "../dist/manifest.json")],

And now dev server will reload the page when manifest.json was changed.

Also you can debug it using:

stats: {
  hash: true
},

And you will see that application wasn't changed, because nothing was changed in dll-user.

Feel free to feedback

[creage]

@alexander-akait Well, since my app uses a dll, it becomes part of it, and changes to dll are changing my app, which should be reflected by reload. And, it used to work up to 5.5.3. I can watch for manifest, but that’s kinda hacky.

[alexander-akait]

@creage The manifest is just a file and just a file dependency, changes in dll didn't change your application code (i.e. dll-user), as I said above you can see hash was not changed when you done a change in dll, for example just create index.html manually and add the script tags and you will see the same behaviour, html-webpack-plugin had a bug and changed a hash, but should not do it