Persistent caching return stale results when updating resolve.alias

Bug report

What is the current behavior?

When changing resolve.alias, affected persistent cache entries are still used instead of being evited.

If the current behavior is a bug, please provide the steps to reproduce.

I’m using the filesystem cache with resolve aliases:

const myAliases = {
 "@theme/MyComponent": "/dirname/OLD_COMPONENT.js",
};

module.exports = {
  cache: {
    type: "filesystem",
  },
  resolve: { alias: myAliases }
}

Now, let’s change the aliases:

const myAliases = {
 "@theme/MyComponent": "/dirname/NEW_COMPONENT.js",
};

module.exports = {
  cache: {
    type: "filesystem",
  },
  resolve: { alias: myAliases }
}

When building/running again (dev server or prod), Webpack will keep using the code from OLD_COMPONENT.js, while it should rather use NEW_COMPONENT.js

When cleaning node_modules/.cache/webpack, the next build will use NEW_COMPONENT.js successfully.

What is the expected behavior?

I would expect Webpack to be able to discard cache entries that are affected by the alias changes.

A workaround is to use cache.version to discard the whole cache when aliases are updated, but this is a bit too aggressive to clean the whole cache for a single alias change.

const myAliases = {
 "@theme/MyComponent": "/dirname/NEW_COMPONENT.js",
};

module.exports = {
  cache: {
    type: "filesystem",
    version: md5HashString(myAliases),
  },
  resolve: { alias: myAliases }
}

Doc says:

Update the version when configuration changed in a way which doesn’t allow to reuse cache.

It is not totally clear to me what configuration changes are handled by webpack, and what configuration changes should we handle in userland. I think it would be nice to have this supported in webpack core as it’s hard to implement in an efficient way in userland.

Other relevant information: webpack version: 5.40 Node.js version: 14.x Operating System: macos sierra Additional tools:

[alexander-akait]

No problems here… How you run webpack? If you use webpack-cli we automatically added your configuration as buildDependencies https://github.com/webpack/webpack-cli/blob/master/packages/webpack-cli/lib/webpack-cli.js#L1855, so any changes in file will invalidate cache, but if you use external file you need do it manually, also we have https://webpack.js.org/configuration/other-options/#cacheversion for this purpose

[alexander-akait]

Was wondering if Webpack offers any API for imperatively invalidate/manipulate some cache entries.

in theory it is possible, here we implement logic for resolving https://github.com/webpack/webpack/blob/master/lib/cache/ResolverCachePlugin.js, also we have hooks for get/store cache