Typed rules by vidit-od · Pull Request #5025 · haskell/haskell-language-server

vidit-od · 2026-07-23T20:27:34Z

Introduces Hierarchical Typed Rules

wz1000

Broadly looks good, some inputs need to be tightened up

Store SomeInput in Shake keys and route rule lookup helpers through typed RuleInput values instead of raw normalized file paths. This also updates tracing and no-file handling to work with the typed key representation.

Thread SomeFileInput, SomeHaskellInput, and ProjectHaskellInput through file store, HIE indexing, and module rules. Add a generic input reclassification helper so call sites can move between compatible typed rule inputs without bespoke wrappers.

Thread typed rule inputs through core Shake helpers, file-store state, dependency graph lookups, and LSP request handlers. Convert raw normalized paths at API boundaries so project, Haskell, and general file rules receive the appropriate input type.

Builds Ghcide, removes helpers that are not used or should not be used

Carry ProjectHaskellInput through dependency information, import lookup, reverse dependency traversal, HIE reads, and eval/reference paths instead of round-tripping through NormalizedFilePath. This keeps non-project Haskell inputs out of project-only rules while preserving the typed inputs needed by downstream Shake rules.

Track project Haskell inputs in session state, known targets, VFS-backed services, and caches. Migrate hover, notes, eval, and semantic token rules to use their typed inputs directly.

fendor

Thanks, this looks very nice! This is a nitpick review, so it is the intention to be done after the review is addressed. I have reviewed the ghcide changes, will review plugins soon.

Further, we agreed the following documentation is still missing and will be added:

    * What are the existing rules?
    * What is RuleInput?
    * Why do we have RuleInput
    * What is the design of RuleInput
        Note [Hierarchical Inputs]
        Note [RuleInput]
        
        Reference these notes from various type classes and RuleInput type
    * Helper functions need documentation

fendor · 2026-07-31T11:37:20Z

 toPriority :: PluginError -> Priority
 toPriority (PluginInternalError _)    = Error
 toPriority (PluginInvalidParams _)    = Warning
+toPriority (PluginUnsupportedUriType _) = Warning


We might want to demote this to Debug. IIRC, a warning is displayed in the editor, but these errors will be perfectly sensible in the future, right?

@wz1000 opinions?

fendor

Some more comments :)

fendor · 2026-08-09T09:51:58Z

+Within this hierarchy, a parent accepts all descendants. Upcasting wraps a child
+in each parent constructor, then uses 'toInput' for 'SomeInput'; for example,
+'ProjectHaskellInput' -> 'SomeHaskellInput' -> 'SomeFileInput' -> 'SomeInput'.
+'fromInput' performs the checked downcast and succeeds only within its branch.


What does a parent accepts all descendants mean?

fendor · 2026-08-09T10:13:19Z

+          case file of
+            SomeProjectHaskellInput projectFile ->
+              setFileModified (cmapWithPrio LogFileStore recorder) (VFSModified vfs) ide False projectFile action
+            _ -> setSomethingModified (VFSModified vfs) ide (fromNormalizedFilePath (inputFilePath file) ++ " (modified)") action


We shouldn't do anything here, rather log this case.

@wz1000 What should we do in this case? Call setSomethingModified for completeness? We need to add it to the set of files of interest, but it might not need to record that it isn't the first time this non project haskell file was opened, right? 🤔

fendor · 2026-08-09T10:13:50Z

+          case file of
+            SomeProjectHaskellInput projectFile ->
+              setFileModified (cmapWithPrio LogFileStore recorder) (VFSModified vfs) ide False projectFile action
+            _ -> setSomethingModified (VFSModified vfs) ide (fromNormalizedFilePath (inputFilePath file) ++ " (modified)") action


Should we set something modified here? What does this do?

fendor · 2026-08-09T10:14:09Z

+            case file of
+              SomeProjectHaskellInput projectFile ->
+                setFileModified (cmapWithPrio LogFileStore recorder) (VFSModified vfs) ide True projectFile action
+              _ -> setSomethingModified (VFSModified vfs) ide (fromNormalizedFilePath (inputFilePath file) ++ " (modified)") action


fendor · 2026-08-09T12:09:20Z

+    let mbFile = case inputFingerprint input of
+          InputFile file -> Just file
+          _              -> Nothing


Move this into inProgress notification change

fendor · 2026-08-09T12:09:58Z

+            --  * creating a dependency: If everything depends on GetModificationTime, we lose early cutoff
+            --  * creating bogus "file does not exists" diagnostics
+            | otherwise -> useWithoutDependency (GetModificationTime_ False) (toSomeFileInput file)
+          _ -> pure Nothing


Please list out all the possible cases here. I think that's better, even though the rhs is going to be identical for each

fendor · 2026-08-09T12:10:59Z

+          -- GHC import paths are untyped and may include generated dependency roots;
+          -- retain only project Haskell inputs.


Which generated dependency roots? Where would this come from?

fendor · 2026-08-09T12:17:48Z

 resolveCompletion ide _pid comp@CompletionItem{_detail,_documentation,_data_} uri (CompletionResolveData _ needType (NameDetails mod occ)) =
  do
-    file <- getNormalizedFilePathE uri
+    projectInput <- withExceptT (const PluginStaleResolve) $ classifyAsHaskell uri


Wrong classifier if completions only work with ProjectHaskell files, right?

fendor · 2026-08-09T12:20:34Z

-parseActions :: CI String -> [NormalizedFilePath] -> Action (Either Text [Bool])
-parseActions "typecheck" fps = Right . fmap isJust <$> uses TypeCheck fps
-parseActions "getLocatedImports" fps = Right . fmap isJust <$> uses GetLocatedImports fps
-parseActions "getmodsummary" fps = Right . fmap isJust <$> uses GetModSummary fps
-parseActions "getmodsummarywithouttimestamps" fps = Right . fmap isJust <$> uses GetModSummaryWithoutTimestamps fps
-parseActions "getparsedmodule" fps = Right . fmap isJust <$> uses GetParsedModule fps
-parseActions "ghcsession" fps = Right . fmap isJust <$> uses GhcSession fps
-parseActions "ghcsessiondeps" fps = Right . fmap isJust <$> uses GhcSessionDeps fps
-parseActions "gethieast" fps = Right . fmap isJust <$> uses GetHieAst fps
-parseActions "getFileContents" fps = Right . fmap isJust <$> uses GetFileContents fps
-parseActions other _ = return $ Left $ "Cannot parse ide rule: " <> pack (original other)
+parseActions :: CI String -> [SomeFileInput] -> Action (Either Text [Bool])
+parseActions action fps
+    | action == fromString "typecheck"
+    , Just pFiles <- traverse projectFile fps =
+        fmap (Right . map isJust) (uses TypeCheck pFiles)
+  where
+    projectFile (SomeFileHaskellInput (SomeProjectHaskellInput pFile)) = Just pFile
+    projectFile _ = Nothing
+parseActions action fps = sequence <$> traverse (parseAction action) fps


What is going on here?

vidit-od requested review from fendor, michaelpj and wz1000 as code owners July 23, 2026 20:27

wz1000 reviewed Jul 24, 2026

View reviewed changes

Comment thread ghcide/src/Development/IDE/Core/Actions.hs Outdated

wz1000 reviewed Jul 24, 2026

View reviewed changes

Comment thread ghcide/src/Development/IDE/Core/RuleInput.hs Outdated

wz1000 reviewed Jul 24, 2026

View reviewed changes

Comment thread ghcide/src/Development/IDE/Core/Rules.hs Outdated

wz1000 reviewed Jul 24, 2026

View reviewed changes

Comment thread ghcide/src/Development/IDE/Core/Rules.hs Outdated

wz1000 reviewed Jul 30, 2026

View reviewed changes

vidit-od requested review from 0rphee, July541, crtschin, drsooch, eddiemundo, georgefst, jian-lin, joyfulmantis, jvanbruegge, kokobd, konn, ozkutuk and soulomoon as code owners July 31, 2026 08:19

vidit-od added 9 commits July 31, 2026 08:36

rule system setup

56170d8

Represent Shake keys with typed rule inputs

50ae5f1

Store SomeInput in Shake keys and route rule lookup helpers through typed RuleInput values instead of raw normalized file paths. This also updates tracing and no-file handling to work with the typed key representation.

Use typed file inputs in core rules

7bc5d41

Thread SomeFileInput, SomeHaskellInput, and ProjectHaskellInput through file store, HIE indexing, and module rules. Add a generic input reclassification helper so call sites can move between compatible typed rule inputs without bespoke wrappers.

a few more migrations

1e5a37c

Use typed inputs for ghcide rules

fb506ac

Thread typed rule inputs through core Shake helpers, file-store state, dependency graph lookups, and LSP request handlers. Convert raw normalized paths at API boundaries so project, Haskell, and general file rules receive the appropriate input type.

Refactor and remove

ec31892

Builds Ghcide, removes helpers that are not used or should not be used

fix atpoint

1dedf55

Propagate typed file inputs through sessions and plugins

8bd779f

Track project Haskell inputs in session state, known targets, VFS-backed services, and caches. Migrate hover, notes, eval, and semantic token rules to use their typed inputs directly.

vidit-od added 5 commits July 31, 2026 08:39

fix signatures

edcd830

plugin migration p1

11591e8

plugin migration p2

0c0cf39

plugin migrtion p3

f8f168a

ghcide tests fix

330adaf

vidit-od force-pushed the Typed-Rules branch from 33a2c2a to 330adaf Compare July 31, 2026 08:49

fendor requested changes Jul 31, 2026

View reviewed changes

vidit-od force-pushed the Typed-Rules branch 3 times, most recently from 0e49c0f to 330adaf Compare August 4, 2026 05:45

Reviews 1

ec6e677

vidit-od force-pushed the Typed-Rules branch 4 times, most recently from 144b524 to ec6e677 Compare August 4, 2026 20:50

vidit-od added 2 commits August 4, 2026 20:50

Stylish haskell

492bb1f

Reviews 2

068c569

vidit-od force-pushed the Typed-Rules branch from d567a1a to 912f9da Compare August 8, 2026 08:50

Reviews 3

63ef976

vidit-od force-pushed the Typed-Rules branch from 912f9da to 63ef976 Compare August 8, 2026 09:20

Reviews 4

0afd603

vidit-od force-pushed the Typed-Rules branch from bc09427 to 0afd603 Compare August 8, 2026 13:06

fendor requested changes Aug 9, 2026

View reviewed changes

fendor reviewed Aug 9, 2026

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		-- GHC import paths are untyped and may include generated dependency roots;
		-- retain only project Haskell inputs.

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vidit-od commented Jul 23, 2026 •

edited

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