Space leak in persistentHieFileRule

[pepeiborra]

haskell-language-server/ghcide/src/Development/IDE/Core/Rules.hs

Lines 506 to 513 in e0a4642

	(currentSource,ver) <- liftIO $ do
	mvf <- getVirtualFile vfs $ filePathToUri' file
	case mvf of
	Nothing -> (,Nothing) . T.decode encoding <$> BS.readFile (fromNormalizedFilePath file)
	Just vf -> pure (Rope.toText $ _text vf, Just $ _lsp_version vf)
	let refmap = generateReferencesMap . getAsts . hie_asts $ res
	del = deltaFromDiff (T.decode encoding $ hie_hs_src res) currentSource
	pure (HAR (hie_module res) (hie_asts res) refmap mempty (HieFromDisk res),del,ver)

del in line 512 keeps two large byte strings alive:

• source code of the .hs file on disk
• source code recorded in the .hie file

This is leaked for all the modules in the project with an entry in the hiedb and a .hie file (all in most circumstances).

The memory leak is not flushed until the HieAstResult is actually used and the PositionMapping is forced.

[pepeiborra]

persistentHieFile is only used at startup to load data before the build graph has been initialised, and the results it provides will be short-lived (hopefully) so I'm not sure how much this is an issue in practice.

[jneira]

This continue being a problem after the perf improvements post-1.4.0?

[michaelpj]

@wz1000 is this still a problem?