[import/no-extraneous-dependencies] Doesn't properly clear the dependency cache

[martonperei]

The dependencies from package.json are cached for this rule, but it looks like when eslint is running as a daemon, like an IDE (VSCode or IntelliJ IDEA), the cache is not cleared properly, causing errors to keep showing if package.json is modified.
It looks like Program:exit is defined in the wrong place in the rule. I'm not sure what the intended behavior was, but to me it looks like a simple bug, as Program:exit should be returned from create like so:

create(context) {
  [...]
  return {
    ...moduleVisitor((source, node) => {
      reportIfMissing(context, deps, depsOptions, node, source.value);
    }, { commonjs: true }),
    'Program:exit'() {
      depFieldCache.clear();
    },
  }
}

instead, Program:exit is defined on the same level as create, causing it to be ignored.
Though as Program:exit is ran for each file, the cache would be quite useless in this case. Perhaps the file modified time could be checked to trigger a reload, but I'm also not seeing any slowdowns from not caching at all, but that might just be for my use case. (the bulk of the time is spent in reportInMissing ~677ms (because of the typescript resolver) vs ~30ms in getDependencies (uncached))
Can anyone confirm?

[ljharb]

Looks like the Program:exit visitor was added in 7f251b2 / #2374, and I agree with you that it should be inside the create, object-assigned onto the moduleVisitor return value - however, as you note, fixing this would cause the cache to be cleared after every file, and probably slow down the lint rule significantly.

eslint isn't designed to run as a daemon, and thus shouldn't be - there's no signalling built into eslint that would enable a long-running cache to clear things efficiently.