Add expandable hover by jakebailey · Pull Request #3311 · microsoft/typescript-go

jakebailey · 2026-04-01T04:41:52Z

This is a proposed VS Code feature. To make this work, we add the new API ontop of the LSP, then disable the LSP client's hover provider, in favor of one with the feature.

Copilot

Pull request overview

This PR adds an “expandable hover” feature end-to-end: a proposed VS Code hover API that can request increased “verbosity”, an LSP extension (verbosityLevel on HoverParams + canIncreaseVerbosity on Hover), server plumbing to honor it, and fourslash coverage/baselines for the new hover behavior.

Changes:

Extend LSP hover request/response shapes to support verbosity (verbosityLevel) and server-provided expandability (canIncreaseVerbosity).
Add a VS Code extension hover provider that uses the proposed hover verbosity API and sends verbosityLevel over LSP (disabling the languageclient’s built-in hover).
Add fourslash harness support + many new baselines/tests for hover verbosity scenarios, plus conversion-script support for verify.baselineQuickInfo({...}).

Reviewed changes

Copilot reviewed 91 out of 93 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
`internal/lsp/server.go`	Routes hover requests to verbose hover implementation when `verbosityLevel` is present.
`internal/lsp/lsproto/lsp_generated.go`	Adds `verbosityLevel` to `HoverParams`, `canIncreaseVerbosity` to `Hover`, and a capabilities flag.
`internal/lsp/lsproto/_generate/generate.mts`	Patches the LSP model so the generator emits the new hover fields/capabilities.
`_extension/src/languageFeatures/hover.ts`	New VS Code hover provider that requests verbose hover via LSP and maps expand/decrease flags.
`_extension/src/vscode.proposed.editorHoverVerbosityLevel.d.ts`	Declares the proposed VS Code API surface (`VerboseHover`, `HoverContext`, etc.).
`_extension/src/client.ts`	Advertises hover verbosity capability + registers the custom hover provider; disables LSP hover via middleware.
`_extension/package.json`	Enables the `editorHoverVerbosityLevel` proposal and bumps VS Code engine/types.
`package-lock.json`	Updates VS Code typings version to match the engine bump.
`internal/checker/printer.go`	Adds verbosity-aware type/signature/symbol-to-declaration stringification helpers.
`internal/checker/nodebuilder.go`	Adds verbosity-aware nodebuilder entry points and symbol-declaration rendering helpers.
`internal/checker/services.go`	Introduces `Checker.IsLibType` used to prevent expanding default-lib types.
`internal/ls/completions.go`	Refactors completion item detail generation; threads hover quickinfo via the updated quickinfo helper signature.
`internal/ls/string_completions.go`	Updates call into completion details helper after signature refactor.
`internal/fourslash/fourslash.go`	Adds `VerifyBaselineHoverWithVerbosity` helper for producing multi-verbosity hover baselines.
`internal/fourslash/baselineutil.go`	Uses stable sorting when inserting multiple tooltips at the same position.
`internal/fourslash/_scripts/convertFourslash.mts`	Adds support for `verify.baselineQuickInfo({...verbosity...})` conversion into Go tests.
`internal/fourslash/_scripts/unparsedTests.txt`	Removes now-supported quickinfoVerbosity tests from the “unparsed” list.
`internal/fourslash/_scripts/failingTests.txt`	Updates the list of failing tests (removals).
`internal/fourslash/tests/quickinfoVerbosityNamespaceDefaultExport_test.go`	New manual fourslash test for namespace default export verbosity behavior.
`internal/fourslash/tests/gen/quickinfoVerbosity1_test.go`	Generated hover verbosity test.
`internal/fourslash/tests/gen/quickinfoVerbosity2_test.go`	Generated hover verbosity test.
`internal/fourslash/tests/gen/quickinfoVerbosity3_test.go`	Generated hover verbosity test.
`internal/fourslash/tests/gen/quickinfoVerbosityClass1_test.go`	Generated hover verbosity test.
`internal/fourslash/tests/gen/quickinfoVerbosityClass2_test.go`	Generated hover verbosity test.
`internal/fourslash/tests/gen/quickinfoVerbosityConditionalType_test.go`	Generated hover verbosity test.
`internal/fourslash/tests/gen/quickinfoVerbosityEnum_test.go`	Generated hover verbosity test.
`internal/fourslash/tests/gen/quickinfoVerbosityFunction_test.go`	Generated hover verbosity test.
`internal/fourslash/tests/gen/quickinfoVerbosityImport_test.go`	Generated hover verbosity test.
`internal/fourslash/tests/gen/quickinfoVerbosityIndexedAccessType_test.go`	Generated hover verbosity test.
`internal/fourslash/tests/gen/quickinfoVerbosityIndexSignature_test.go`	Generated hover verbosity test.
`internal/fourslash/tests/gen/quickinfoVerbosityIndexType_test.go`	Generated hover verbosity test.
`internal/fourslash/tests/gen/quickinfoVerbosityInterface1_test.go`	Generated hover verbosity test.
`internal/fourslash/tests/gen/quickinfoVerbosityInterface2_test.go`	Generated hover verbosity test.
`internal/fourslash/tests/gen/quickinfoVerbosityIntersection1_test.go`	Generated hover verbosity test.
`internal/fourslash/tests/gen/quickinfoVerbosityJs_test.go`	Generated hover verbosity test.
`internal/fourslash/tests/gen/quickinfoVerbosityLibType_test.go`	Generated hover verbosity test.
`internal/fourslash/tests/gen/quickinfoVerbosityMappedType_test.go`	Generated hover verbosity test.
`internal/fourslash/tests/gen/quickinfoVerbosityNamespace_test.go`	Generated hover verbosity test.
`internal/fourslash/tests/gen/quickinfoVerbosityNamespaceDefaultExport_test.go`	Generated hover verbosity test.
`internal/fourslash/tests/gen/quickinfoVerbosityNoErrorTruncation1_test.go`	Generated hover verbosity test.
`internal/fourslash/tests/gen/quickinfoVerbosityObjectType1_test.go`	Generated hover verbosity test.
`internal/fourslash/tests/gen/quickinfoVerbosityRecursiveType_test.go`	Generated hover verbosity test.
`internal/fourslash/tests/gen/quickinfoVerbosityServer_test.go`	Generated hover verbosity test (server mode).
`internal/fourslash/tests/gen/quickinfoVerbosityToplevelTruncation1_test.go`	Generated hover verbosity test.
`internal/fourslash/tests/gen/quickinfoVerbosityToplevelTruncation2_test.go`	Generated hover verbosity test.
`internal/fourslash/tests/gen/quickinfoVerbosityTruncation1_test.go`	Generated hover verbosity test.
`internal/fourslash/tests/gen/quickinfoVerbosityTruncation2_test.go`	Generated hover verbosity test.
`internal/fourslash/tests/gen/quickinfoVerbosityTuple_test.go`	Generated hover verbosity test.
`internal/fourslash/tests/gen/quickinfoVerbosityTypeof_test.go`	Generated hover verbosity test.
`internal/fourslash/tests/gen/quickinfoVerbosityTypeParameter_test.go`	Generated hover verbosity test.
`testdata/baselines/reference/fourslash/quickInfo/quickinfoVerbosity1.baseline`	New hover verbosity baseline.
`testdata/baselines/reference/fourslash/quickInfo/quickinfoVerbosity2.baseline`	New hover verbosity baseline.
`testdata/baselines/reference/fourslash/quickInfo/quickinfoVerbosityConditionalType.baseline`	New hover verbosity baseline.
`testdata/baselines/reference/fourslash/quickInfo/quickinfoVerbosityFunction.baseline`	New hover verbosity baseline.
`testdata/baselines/reference/fourslash/quickInfo/quickinfoVerbosityIndexSignature.baseline`	New hover verbosity baseline.
`testdata/baselines/reference/fourslash/quickInfo/quickinfoVerbosityIndexType.baseline`	New hover verbosity baseline.
`testdata/baselines/reference/fourslash/quickInfo/quickinfoVerbosityIndexedAccessType.baseline`	New hover verbosity baseline.
`testdata/baselines/reference/fourslash/quickInfo/quickinfoVerbosityIntersection1.baseline`	New hover verbosity baseline.
`testdata/baselines/reference/fourslash/quickInfo/quickinfoVerbosityLibType.baseline`	New hover verbosity baseline.
`testdata/baselines/reference/fourslash/quickInfo/quickinfoVerbosityMappedType.baseline`	New hover verbosity baseline.
`testdata/baselines/reference/fourslash/quickInfo/quickinfoVerbosityNamespaceDefaultExport.baseline`	New hover verbosity baseline.
`testdata/baselines/reference/fourslash/quickInfo/quickinfoVerbosityNoErrorTruncation1.baseline`	New hover verbosity baseline.
`testdata/baselines/reference/fourslash/quickInfo/quickinfoVerbosityObjectType1.baseline`	New hover verbosity baseline.
`testdata/baselines/reference/fourslash/quickInfo/quickinfoVerbosityRecursiveType.baseline`	New hover verbosity baseline.
`testdata/baselines/reference/fourslash/quickInfo/quickinfoVerbosityServer.baseline`	New hover verbosity baseline.
`testdata/baselines/reference/fourslash/quickInfo/quickinfoVerbosityTruncation1.baseline`	New hover verbosity baseline.
`testdata/baselines/reference/fourslash/quickInfo/quickinfoVerbosityToplevelTruncation1.baseline`	New hover verbosity baseline.
`testdata/baselines/reference/fourslash/quickInfo/quickinfoVerbosityToplevelTruncation2.baseline`	New hover verbosity baseline.
`testdata/baselines/reference/fourslash/quickInfo/quickinfoVerbosityTypeof.baseline`	New hover verbosity baseline.
`testdata/baselines/reference/fourslash/quickInfo/quickinfoVerbosityTypeParameter.baseline`	New hover verbosity baseline.
`testdata/baselines/reference/fourslash/quickInfo/quickInfoDisplayPartsTypeParameterInFunction.baseline`	Updates baseline output for type parameter/parameter quickinfo display parts.
`testdata/baselines/reference/fourslash/quickInfo/quickInfoDisplayPartsTypeParameterInClass.baseline`	Updates baseline output for class type parameter/parameter quickinfo display parts.
`testdata/baselines/reference/fourslash/quickInfo/quickInfoDisplayPartsTypeParameterInTypeAlias.baseline`	Updates baseline output for type parameter quickinfo display parts.
`testdata/baselines/reference/fourslash/quickInfo/quickInfoDisplayPartsTypeParameterInFunctionLikeInTypeAlias.baseline`	Updates baseline output for type parameter quickinfo display parts.
`testdata/baselines/reference/fourslash/quickInfo/quickInfoDisplayPartsEnum1.baseline`	Updates enum quickinfo baseline (e.g. `const enum` rendering).
`testdata/baselines/reference/fourslash/quickInfo/quickInfoDisplayPartsEnum2.baseline`	Updates enum quickinfo baseline (e.g. `const enum` rendering).
`testdata/baselines/reference/fourslash/quickInfo/quickInfoDisplayPartsEnum3.baseline`	Updates enum quickinfo baseline (e.g. `const enum` rendering).
`testdata/baselines/reference/submodule/compiler/privateFieldsInClassExpressionDeclaration.js`	Updates compiler baseline output for private fields in .d.ts emit.
`testdata/baselines/reference/submodule/compiler/privateFieldsInClassExpressionDeclaration.js.diff`	Updates compiler baseline diff for the same private field emit change.

Copilot · 2026-04-01T22:41:25Z

internal/fourslash/_scripts/convertFourslash.mts

+    const verbosityLevels: Record<string, number[]> = {};
+    for (const prop of verbosityArg.properties) {
+        if (!ts.isPropertyAssignment(prop)) {
+            return undefined;
+        }
+        let name: string;
+        if (ts.isIdentifier(prop.name) || ts.isStringLiteral(prop.name)) {
+            name = prop.name.text;
+        }
+        else if (ts.isNumericLiteral(prop.name)) {
+            name = prop.name.text;
+        }
+        else {
+            return undefined;
+        }
+        if (ts.isArrayLiteralExpression(prop.initializer)) {
+            const levels: number[] = [];
+            for (const elem of prop.initializer.elements) {
+                if (!ts.isNumericLiteral(elem)) {
+                    return undefined;
+                }
+                levels.push(Number(elem.text));
+            }
+            verbosityLevels[name] = levels;
+        }
+        else if (ts.isNumericLiteral(prop.initializer)) {
+            verbosityLevels[name] = [Number(prop.initializer.text)];
+        }
+        else {
+            return undefined;
+        }


parseBaselineQuickInfo is declared to return VerifyBaselineQuickInfoCmd[], but several branches return undefined (e.g. when encountering unsupported property shapes). With strict: true in this folder’s tsconfig, this won’t type-check and will break the fourslash conversion scripts. Replace these return undefined paths with throw new Error(...) (or change the function’s return type to include undefined and handle it at the call site).

internal/checker/services.go

internal/lsp/lsproto/_generate/generate.mts

Copilot · 2026-04-01T22:41:26Z

...aselines/reference/fourslash/quickInfo/quickInfoDisplayPartsTypeParameterInFunction.baseline

 //                                 ^
 // | ----------------------------------------------------------------------
 // | ```tsx
-// | (parameter) a: U
+// | (parameter) a: U extends string
 // | ```


The hover text shows (parameter) a: U extends string, which is not valid TypeScript type syntax for a parameter (the parameter’s type is U; the extends string part is a constraint on the type parameter declaration). This looks like a regression in quickinfo rendering for constrained type parameters; the hover should keep the parameter type as U (while type parameter hovers can show the constraint).

Copilot · 2026-04-01T22:41:26Z

...a/baselines/reference/fourslash/quickInfo/quickInfoDisplayPartsTypeParameterInClass.baseline

 //                 ^
 // | ----------------------------------------------------------------------
 // | ```tsx
-// | (parameter) a: T
+// | (parameter) a: T extends c<string>
 // | ```
 // | 


The baseline now renders constructor/method parameters as T extends c<string> / U extends c<string>, which is not valid parameter type syntax (constraints belong on the type parameter declarations, not at use sites). This suggests the quickinfo printer is incorrectly formatting type parameter uses as declarations when constrained.

jakebailey · 2026-04-01T23:09:07Z

One icky thing is that symbolTableToDeclarationStatements is basically what used to power JS declaration emit, but now does not; everything here seems to be requiredish but the unported code is all JS stuff. Makes me wonder if this feature just needs a rethink now that we aren't doing JS in the same way?

internal/fourslash/_scripts/convertFourslash.mts

internal/fourslash/_scripts/failingTests.txt

internal/ls/completions.go

internal/ls/hover.go

internal/checker/printer.go

internal/checker/nodebuilder.go

internal/checker/printer.go

internal/ls/hover.go

internal/checker/nodebuilderimpl.go

internal/checker/nodebuilder_hover.go

gabritto · 2026-04-07T16:10:03Z

internal/checker/nodebuilderimpl.go

+// At maxExpansionDepth <= 0, no expansion will occur so we return false to allow type-node reuse.
 func (b *NodeBuilderImpl) canPossiblyExpandType(t *Type) bool {
-	if b.ctx.maxExpansionDepth < 0 {
+	if b.ctx.maxExpansionDepth <= 0 {


Why did this change? Couldn't we still fall into the case where maxDepth is 0 and depth is 0 and canIncreaseExpansionDepth is false and so this would return true before?

This is the bit that makes it so that simply enabling the client capability / sending level 0 does not change the output formatting. But otherwise I'm not sure what you mean

Yeah, but IIRC if we have a request with level set to 0, and we make canPossiblyExpandType return false, we will do type node reuse and not compute canIncreaseVerbosityLevel.

Ah, yeah, we have to still do a little work I guess so this is set. I guess I didn't notice because the boolean is hidden if false, but obviously fourslash will keep querying with higher levels. Probably I should assert if we attempt to go higher but the previous response said no... maybe.

jakebailey added 16 commits March 31, 2026 20:53

Add expandable hover

ae3c01c

more

6672f83

More improvements

c04dbb1

Fix enclosing declaration difference, unique to expansion

ed164e0

fix multiline signature outputs

ce34b98

Fix namespace printing

d84d8ad

Fix widening

27f8c19

Fix incorrect namespace keyword

ef76c95

Fix nested namespaces

c958dbd

Change truncation message

d35cb55

cleanups

0dbcf62

Misc fixes

69dc631

Remove canDecreaseVerbosity

d06340e

Raise minimum vscode version

deec44d

Simplify

6de6ddf

Reorder funcs

872b756

jakebailey mentioned this pull request Apr 1, 2026

Disallow explicit null for optional fields #3313

Merged

jakebailey added 4 commits April 1, 2026 11:51

Remove duped helper

372856c

isConstantVariable

9d55ae5

drop weird pointer

cbdfd52

TODOs

502e820

jakebailey requested a review from gabritto April 1, 2026 20:23

jakebailey added 4 commits April 1, 2026 14:39

export default rewrite

635fc5f

Fix mistaken export keyword

fbf80c4

Merge branch 'main' into jabaile/expand-hover

04a1866

regen

2409c64

jakebailey marked this pull request as ready for review April 1, 2026 22:29

Copilot AI review requested due to automatic review settings April 1, 2026 22:29

Copilot started reviewing on behalf of jakebailey April 1, 2026 22:31 View session

Copilot AI reviewed Apr 1, 2026

View reviewed changes

jakebailey added 3 commits April 1, 2026 16:16

clarify that the missing code is all about js decl emit

fe7b67f

More simplification in light of context

b96e1e5

Add tests

4496908

gabritto reviewed Apr 2, 2026

View reviewed changes

jakebailey added 4 commits April 2, 2026 15:58

Totally redo from scratch

7164780

Fix convertFourslash

d30fa20

Fix convertFourslash

9195c03

Revert weird completions changes

a251fbb

jakebailey mentioned this pull request Apr 3, 2026

Implement multi-file doc highlights #3334

Open

Fix expansion conditional

14059a0

gabritto reviewed Apr 6, 2026

View reviewed changes

jakebailey added 2 commits April 6, 2026 13:24

PR feedback

08a85ec

Just move vc into sig

2a4c91f

jakebailey requested a review from gabritto April 6, 2026 20:32

gabritto reviewed Apr 7, 2026

View reviewed changes

Handle canIncreaseVerbosity even when reusing nodes

7c9361b

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jakebailey commented Apr 1, 2026 •

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