Ide rebuild can create invalid JS with outdated cache

[kritzcreek]

1. Compile and load these 2 modules into the ide server:

module A where

fn :: Int -> String
fn x = show x

module B where

import A (fn)

bFn :: String
bFn = fn 1

2. Change module A.fn to

fn :: String -> String
fn s = s <> "hi!"

3. Recompile A without letting the server know (start it with the --editor-mode flag and recompile module A from the cmdline with purs compile src/A.purs)

4. Make a change to module B and fast-rebuild through ide, it does not show any errors, and it continues to generate code for B that assumes the old signature of A.fn is still valid, but instead the code fails at runtime.

This is a known issue, and I do not have a satisfying solution for the problem at hand. It basically boils down to cache invalidation between the FS and the ide servers internal state. Empirically file watching misses changes, and doesn't interact well with adding and removing files and avoiding it by polling creates too much overhead.

[i-am-the-slime]

When I rename a module a few times I always get outdated suggestions/completions from the previous module names.

I'm also worried about this leaking memory.

Since 3.16.0 there have been hooks in the LSP for when files are added/removed: "Events for file operations (create, rename, delete)". Could we use these to signal to the IDE server when something needs invalidating?