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

vidit-od · 2026-07-23T20:27:34Z

This PR introduces typed inputs for HLS/ghcide rules.

HLS already associates every rule key with its result through RuleResult, but all rules previously accepted the same input type: NormalizedFilePath. Theis PR adds an open type family that associates each rule with the kind of input it supports:

type family RuleInput k

type instance RuleInput TypeCheck = ProjectHaskellInput
type instance RuleResult TypeCheck = TcModuleResult

Rule inputs are now part of the rule's contract, just like rule results.

Why this is needed

A raw NormalizedFilePath does not tell us what a path actually represent. These distinctions matter. For example, TypeCheck and GhcSession require a project component and session, while file-content rules can work on many file
types. Typed inputs make these assumptions explicit, reject incorrect rule/input pairings earlier, and provide the foundation needed to support dependency sources without treating them as project modules.

How it works

The new Development.IDE.Core.RuleInput module defines this input hierarchy:

SomeInput
|-- NoInput
`-- SomeFileInput
    |-- SomeHaskellInput
    |   |-- ProjectHaskellInput
    |   `-- NonProjectHaskellInput
    |-- CabalInput
    `-- arbitrary NormalizedFilePath

Internally, Shake still needs one heterogeneous key representation. SomeInput
therefore existentially stores typed inputs inside Q, while InputFingerprint
provides consistent equality and hashing.

wz1000

Broadly looks good, some inputs need to be tightened up

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 · 2026-08-09T10:13:19Z

+          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? 🤔

setSomethingModified is not correct here, that will trash the entire session. I think setFileModified should accept SomeHaskellInput instead of ProjectHaskellInput

It should always restart with the new VFS and dirty the file’s GetModificationTime, then run typecheckParents only in the SomeProjectHaskellInput branch

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


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.

wz1000

plugins and input types broadly look correct. I need to do another more careful pass though.

wz1000 · 2026-08-23T11:45:08Z

+isProjectHaskellInput fp = isHaskellFilePath fp && not (isDependencyHaskellPath fp)
+
+isDependencyHaskellPath :: NormalizedFilePath -> Bool
+isDependencyHaskellPath = (".hls/dependencies" `isInfixOf`) . normalise . fromNormalizedFilePath


Let's use something like

isDependencyHaskellPath = isInfixOf [".hls", "dependencies"] . splitDirectories . fromNormalizedFilePath

also normalise is redundant after fromNormalizedFilePath

This let's us avoid issues with path seperators on windows etc.

Perhaps we could even use System.FilePath.Glob, we already have that dependency.

wz1000 · 2026-08-23T11:55:57Z

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


setSomethingModified is not correct here, that will trash the entire session. I think setFileModified should accept SomeHaskellInput instead of ProjectHaskellInput

It should always restart with the new VFS and dirty the file’s GetModificationTime, then run typecheckParents only in the SomeProjectHaskellInput branch

wz1000 · 2026-08-23T11:57:50Z

    deriving anyclass (Hashable, NFData)
 -- GetNotes collects all note definition across all files in the
 -- project. It returns a map from note name to pair of (filepath, position).
+type instance RuleInput GetNotes = SomeFileInput


The comment claims it collects note definitions across all files, then why does it have a SomeFileInput instead of NoInput?

wz1000 · 2026-08-23T11:58:01Z

    deriving anyclass (Hashable, NFData)
 -- GetNoteReferences collects all note references across all files in the
 -- project. It returns a map from note name to list of (filepath, position).
+type instance RuleInput GetNoteReferences = SomeFileInput


same as above.

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

wz1000 reviewed Jul 24, 2026

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

wz1000 reviewed Jul 24, 2026

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

wz1000 reviewed Jul 24, 2026

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

wz1000 reviewed Jul 24, 2026

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

wz1000 reviewed Jul 30, 2026

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

fendor requested changes Jul 31, 2026

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vidit-od force-pushed the Typed-Rules branch 7 times, most recently from 144b524 to ec6e677 Compare August 4, 2026 20:50

vidit-od force-pushed the Typed-Rules branch 2 times, most recently from bc09427 to 0afd603 Compare August 8, 2026 13:06

fendor requested changes Aug 9, 2026

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fendor reviewed Aug 9, 2026

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vidit-od added 22 commits August 18, 2026 07:16

rule system setup

a595aeb

Represent Shake keys with typed rule inputs

067fb12

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

383b24a

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

041d4d3

Use typed inputs for ghcide rules

8895b2c

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

b7e1da1

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

fix atpoint

fa573b5

Propagate typed file inputs through sessions and plugins

11d0717

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.

fix signatures

1ecd6d2

plugin migration p1

674e51e

plugin migration p2

64f3260

plugin migrtion p3

b0b8cf7

ghcide tests fix

62fa949

Reviews 1

26aafb8

Stylish haskell

5d6105e

Reviews 2

3f51e24

Reviews 3

ed0c5c0

Reviews 4

91731e0

Review 5

dc2323a

Review 6

33ca045

Review 7

738800a

vidit-od force-pushed the Typed-Rules branch from 0afd603 to 738800a Compare August 22, 2026 09:49

wz1000 requested changes Aug 23, 2026

View reviewed changes

vidit-od mentioned this pull request Aug 23, 2026

Goto dependency #4973

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Why this is needed

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vidit-od commented Jul 23, 2026 •

edited

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