Generate LSP response types, redo nullable, delete aliases, statically type LSP handlers #1441

jakebailey · 2025-07-23T22:40:36Z

This allows us to work on #1439.

Copilot

Pull Request Overview

This PR implements foundational changes to the LSP protocol type generation system as part of issue #1439. The changes refactor nullable type handling, remove type aliases, and generate request response types.

Replaced custom Nullable[T] with generated union types containing null variants
Removed type alias generation and replaced with direct union type resolution
Added request response type generation for LSP methods
Updated all LSP protocol consumers to use the new generated types

Reviewed Changes

Copilot reviewed 13 out of 14 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
internal/lsp/lsproto/_generate/generate.mts	Core type generation logic overhaul - new nullable handling, union type flattening, response type generation
internal/lsp/lsproto/lsp.go	Removed custom Nullable type, added assertAtMostOne utility function
internal/ls/signaturehelp.go	Updated to use UintegerOrNull instead of Nullable[uint32]
internal/ls/signaturehelp_test.go	Updated test expectations to use new union type syntax
internal/ls/hover.go	Updated to use longer generated union type name
internal/ls/hover_test.go	Updated test expectations for new union type name
internal/ls/diagnostics.go	Refactored to use generated union types and renamed method
internal/ls/definition.go	Updated return types to use generated union types
internal/ls/definition_test.go	Updated test types to match new union types
internal/lsp/server.go	Updated method call to renamed diagnostics function
internal/project/service.go	Updated parameter type to use generated union type
internal/project/service_test.go	Updated test data to use new union type names
internal/fourslash/fourslash.go	Updated to use new union type for content changes

internal/lsp/lsproto/_generate/generate.mts

jakebailey · 2025-07-24T03:12:51Z

Okay, well I went a little overboard. Now, the request/notification handlers are fully statically typed, something I've wanted to do for a while. I also eliminated OrNull for response types, since nil works just as well for those.

jakebailey · 2025-07-24T03:21:08Z

internal/lsp/server.go

-	case *lsproto.InitializedParams:
-		return s.handleInitialized(ctx, req)
-	case *lsproto.DidOpenTextDocumentParams:


Changing how this works is actually a prereq for handling requests with the same params but different methods.

DanielRosenwasser · 2025-07-24T20:38:29Z

internal/fourslash/fourslash.go

 	if resMsg == nil {
 		t.Fatalf(prefix+"Nil response received for completion request", f.lastKnownMarkerName)
 	}
-	result := resMsg.AsResponse().Result
-	switch result := result.(type) {
-	case *lsproto.CompletionList:
-		f.verifyCompletionsResult(t, f.currentCaretPosition, result, expected, prefix)
-	default:
-		t.Fatalf(prefix+"Unexpected response type for completion request: %v", result)
+	if !resultOk {
+		t.Fatalf(prefix+"Unexpected response type for completion request: %T", resMsg.AsResponse().Result)
 	}


It'd be ideal if sendRequest (or a wrapper function) automatically errored based on resMsg and resultOk and used the passed Method for the errors.

I wanted to do this, but it means I have to also pass in prefix which felt strange...

DanielRosenwasser · 2025-07-24T20:41:09Z

internal/fourslash/fourslash.go

@@ -267,20 +267,25 @@ func getCapabilitiesWithDefaults(capabilities *lsproto.ClientCapabilities) *lspr
 	return &capabilitiesWithDefaults
 }

-func (f *FourslashTest) sendRequest(t *testing.T, method lsproto.Method, params any) *lsproto.Message {
+func sendRequest[Params, Resp any](t *testing.T, f *FourslashTest, mapping lsproto.RequestInfo[Params, Resp], params Params) (*lsproto.Message, Resp, bool) {


My nit is that I'd prefer fourslash still come first, but it's fine.

If I do that, then lint rules that say "t comes first" will get mad.

DanielRosenwasser · 2025-07-24T20:42:31Z

internal/lsp/lsproto/_generate/generate.mts

+
+        writeLine(`// Type mapping info for \`${request.method}\``);
+        if (responseTypeName) {
+            writeLine(`var ${methodName}Info = RequestInfo[${paramGoType}, ${responseTypeName}]{Method: Method${methodName}}`);


If you don't like Info, we can call them Mappings, Pairings, ReqRes, or maybe some combo of those.

I had it as "Mapping" before. ReqRes not so much because it has to also work for notifications.

internal/lsp/lsproto/lsp_generated.go

DanielRosenwasser · 2025-07-24T20:49:43Z

internal/lsp/lsproto/lsp.go

+
+// Inspired by https://www.youtube.com/watch?v=dab3I-HcTVk
+
+type RequestInfo[Params, Resp any] struct {


Given the parameter in fourslash is called mapping, maybe it makes sense to at least call this a ParameterResponseMapping or something

That's a mistake; I meant to rename that one too.

internal/lsp/lsproto/lsp_generated.go

…y type LSP handlers (#1441)

jakebailey added 7 commits July 23, 2025 12:06

Flatten ors

49cdeb4

dedupe

5174451

Generate response types and redo nullable

f10463f

or null

a10f21c

Generate response types

d137984

Redo aliases

2dfcb22

Fix

7eb0285

Copilot AI review requested due to automatic review settings July 23, 2025 22:40

Copilot AI reviewed Jul 23, 2025

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jakebailey requested review from DanielRosenwasser, andrewbranch and gabritto July 23, 2025 23:08

DanielRosenwasser approved these changes Jul 23, 2025

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Fix repsonse type names

92b08b2

jakebailey requested a review from DanielRosenwasser July 23, 2025 23:27

DanielRosenwasser approved these changes Jul 23, 2025

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jakebailey added 14 commits July 23, 2025 17:12

Typed handlers

27f3a0d

Fix tests

ac16f29

Rename

baa769f

remove unused

f45bcf6

Rename

f2c67b5

notifiations

901e2ff

Move

2474821

Use method names for switch

ffa8966

Rename

f1ce4fa

Rename

d7ae5a2

Comments

073938b

Consolidate

0ead675

Swap

b3cbf06

Merge branch 'main' into jabaile/lsp-update

1b6c908

jakebailey added 3 commits July 23, 2025 20:04

Fourslash 1

84b8eb8

Fourslash 2

95a3822

Rename

b74c621

jakebailey commented Jul 24, 2025

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jakebailey requested a review from DanielRosenwasser July 24, 2025 17:41

jakebailey enabled auto-merge July 24, 2025 18:10

jakebailey changed the title ~~Generate LSP response types, redo nullable, delete aliases~~ Generate LSP response types, redo nullable, delete aliases, statically type LSP handlers Jul 24, 2025

Defer handler code until after startup since most runs are tsc not lsp

8cb0b69

DanielRosenwasser approved these changes Jul 24, 2025

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jakebailey added this pull request to the merge queue Jul 24, 2025

github-merge-queue bot pushed a commit that referenced this pull request Jul 24, 2025

Generate LSP response types, redo nullable, delete aliases, staticall…

cfb67ad

…y type LSP handlers (#1441)

jakebailey removed this pull request from the merge queue due to a manual request Jul 24, 2025

jakebailey added 3 commits July 24, 2025 14:02

missed one

2afa446

Trim common prefixes in unions

6cfcada

Trim names too

827369b

DanielRosenwasser approved these changes Jul 24, 2025

View reviewed changes

jakebailey enabled auto-merge July 24, 2025 21:38

jakebailey added this pull request to the merge queue Jul 24, 2025

Merged via the queue into main with commit b0ee8b4 Jul 24, 2025
22 checks passed

jakebailey deleted the jabaile/lsp-update branch July 24, 2025 22:01

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Generate LSP response types, redo nullable, delete aliases, statically type LSP handlers #1441

Generate LSP response types, redo nullable, delete aliases, statically type LSP handlers #1441

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		// Inspired by https://www.youtube.com/watch?v=dab3I-HcTVk

		type RequestInfo[Params, Resp any] struct {

Generate LSP response types, redo nullable, delete aliases, statically type LSP handlers #1441

Generate LSP response types, redo nullable, delete aliases, statically type LSP handlers #1441

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Pull Request Overview

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jakebailey commented Jul 24, 2025

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jakebailey Jul 24, 2025 •

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