fix: signature help's active overload not updating - #320980

Peter Wan (peterdanwan) · 2026-06-11T16:10:27Z

fixes Intellisense no longer works for TypeScript function overload #268728
Active overload now updates when typed arguments narrow the overload set

2026-06-11.12-08-10.mp4

Edit: this is consistent with https://www.typescriptlang.org/play/
https://github.com/user-attachments/assets/0c6f8315-dcd9-4487-a655-c3b4f0d7a5bc

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Pull request overview

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Updates TypeScript signature help retrigger behavior to reduce overload-selection flicker while still respecting TypeScript’s updated overload choice when arguments narrow the applicable overload set.

Changes:

Add detailed rationale for how retrigger overload selection should behave.
Only keep the previously active overload on retrigger when it matches TypeScript’s current selectedItemIndex.

Dmitriy Vasyura (dmitrivMS) · 2026-06-11T18:37:28Z

Ok, but we probably need before/after unit-tests to make sure we don't regress anything here.

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Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

Copilot

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

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Copilot reviewed 2 out of 2 changed files in this pull request and generated 5 comments.

Copilot

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

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Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

Copilot

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Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

Peter Wan (peterdanwan) · 2026-06-12T01:09:11Z

Hi Dmitriy Vasyura (@dmitrivMS), after iterating on the code a few times I ended up removing getActiveSignature entirely. The original fix caused both branches of the function to return the same value (info.selectedItemIndex), making it a no-op. The simplest correct approach was to assign result.activeSignature = info.selectedItemIndex directly in provideSignatureHelp, which produces the same behavior without the unnecessary indirection.

For the tests, I did my best to address Copilot's feedback, but I wasn't always sure what it was asking for. I've added unit tests using a mock TS client via _TypeScriptSignatureHelpProvider (VS Code's underscore convention for test-only exports). Happy to hear any suggestions on the test suite if the approach isn't quite right.

- Active overload now updates when typed arguments narrow the overload set

- Instead of searching signatures by label to get an index and comparing it to info.selectedItemIndex, look up signatures[info.selectedItemIndex] directly so both sides of the comparison use the same index source

- Extract getActiveSignature as an exported function so unit tests can import it without the extension host - Add BEFORE suite documenting the original bug: on retrigger, old code returned the stale overload index even after TypeScript updated selectedItemIndex (e.g. after a string argument narrows the overload set on the comma trigger) - Add AFTER suite verifying the fix: retrigger now honours TypeScript's updated selectedItemIndex; the BUG test case that returned 0 now correctly returns 1 Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

- Rename exported helper to computeActiveSignatureIndex to avoid identifier collision with the private method - Stop returning activeSignatureHelp.activeSignature: that index refers to the previous signature list, which is stale if the list reorders between invocations; always use tsSelectedItemIndex instead - Add regression test for the reordering case: verifies that when the list reorders and TS still selects the same overload by label, the current index is returned, not the stale one

- Simplify computeActiveSignatureIndex to only accept tsSelectedItemIndex; the context and signatures params were unused and made the API misleading - Add @internal JSDoc to signal the computeActiveSignatureIndex export is for unit testing only, not public API - Replace assertion-based BEFORE suite with block comment documenting the original bug; asserting known-wrong behaviour institutionalizes incorrect expectations

- Replace the label-matching retrigger guard with result.activeSignature = info.selectedItemIndex; the guard became a no-op after the existingIndex === selectedItemIndex fix and its removal is the correct minimal change - Export TypeScriptSignatureHelpProvider as _TypeScriptSignatureHelpProvider (VS Code underscore-prefix convention for test-only exports) - Add unit tests via mock ITypeScriptServiceClient: documents the old buggy guard behavior and verifies the fix — the FIX test would fail if the label-matching guard were reintroduced

- Move CancellationTokenSource into setup/teardown so it is properly disposed after each test - Add success: true and message: '' to mock response to match the protocol shape - Add @internal test-only export JSDoc to _TypeScriptSignatureHelpProvider to make the export intent explicit

Track TypeScript-selected and user-selected overloads separately so retriggers follow updated recommendations without resetting manual selections. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Dmitriy Vasyura (dmitrivMS) · 2026-07-29T10:26:39Z

Updated the implementation in b05a6e0a648 with a stateful approach.

The direct result.activeSignature = info.selectedItemIndex change fixes #268728, but it also removes the behavior added for #94834: if a user manually selects an overload, that selection should survive subsequent signature-help retriggers.

The new approach:

Records the last signature-help result per document.
Distinguishes the overload automatically selected by TypeScript from an overload explicitly selected by the user through context.activeSignatureHelp.
Follows TypeScript's new selectedItemIndex when argument changes narrow or otherwise change the recommended overload.
Preserves a user-selected overload by label across retriggers and signature-list reordering, falling back to TypeScript when that overload disappears.
Uses per-document request IDs so an obsolete async response cannot overwrite selection state.
Computes the active parameter against the overload that is actually displayed.
Removes the production provider export and protocol-client mock that were added only for tests.

The focused unit tests cover #268728, #94834, automatic and manual selection across reordering, removal of the selected overload, missing or unrelated prior state, and obsolete requests. Validation completed with 7 passing tests, a clean TypeScript extension compile, and hygiene checks.

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Copilot AI review requested due to automatic review settings June 11, 2026 16:10

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Comment thread extensions/typescript-language-features/src/languageFeatures/signatureHelp.ts Outdated

Peter Wan (peterdanwan) changed the title ~~fix: signature help active overload not updating~~ fix: signature help's active overload not updating Jun 11, 2026

vs-code-engineering Bot assigned Matt Bierner (mjbvz) Jun 11, 2026

Peter Wan (peterdanwan) force-pushed the issue-268728 branch from 77c263d to a344241 Compare June 11, 2026 18:17

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Peter Wan (peterdanwan) force-pushed the issue-268728 branch 2 times, most recently from 397850f to 9d77b3d Compare June 11, 2026 22:55

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Peter Wan (peterdanwan) force-pushed the issue-268728 branch from 2311a92 to 114544a Compare June 12, 2026 00:34

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Peter Wan (peterdanwan) force-pushed the issue-268728 branch from 114544a to 9fdf4b3 Compare June 12, 2026 00:50

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Peter Wan (peterdanwan) and others added 3 commits June 12, 2026 15:53

fix: signature help active overload not updating

c9c7d67

- Active overload now updates when typed arguments narrow the overload set

fix: replace findIndex with direct index lookup in getActiveSignature

2d61410

- Instead of searching signatures by label to get an index and comparing it to info.selectedItemIndex, look up signatures[info.selectedItemIndex] directly so both sides of the comparison use the same index source

Peter Wan (peterdanwan) added 4 commits June 12, 2026 15:53

Peter Wan (peterdanwan) force-pushed the issue-268728 branch from 9fdf4b3 to e5d1bec Compare June 12, 2026 19:54

Peter Wan (peterdanwan) requested a review from Dmitriy Vasyura (dmitrivMS) June 12, 2026 20:02

Dmitriy Vasyura (dmitrivMS) and others added 3 commits July 4, 2026 02:26

Merge branch 'main' into issue-268728

2755164

Merge branch 'main' into issue-268728

5f3f41c

Fix signature help overload selection

b05a6e0

Track TypeScript-selected and user-selected overloads separately so retriggers follow updated recommendations without resetting manual selections. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Dmitriy Vasyura (dmitrivMS) requested a review from Copilot July 29, 2026 10:43

Dmitriy Vasyura (dmitrivMS) assigned Dmitriy Vasyura (dmitrivMS) and unassigned Matt Bierner (mjbvz) Jul 29, 2026

Copilot started reviewing on behalf of Dmitriy Vasyura (dmitrivMS) July 29, 2026 10:44 View session

Merge branch 'main' into issue-268728

412e85f

Dmitriy Vasyura (dmitrivMS) enabled auto-merge (squash) July 29, 2026 10:46

Dmitriy Vasyura (dmitrivMS) approved these changes Jul 29, 2026

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Anthony Kim (anthonykim1) approved these changes Jul 29, 2026

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Dmitriy Vasyura (dmitrivMS) merged commit 69e459e into microsoft:main Jul 29, 2026
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vs-code-engineering Bot mentioned this pull request Jul 29, 2026

Intellisense no longer works for TypeScript function overload #268728

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vs-code-engineering Bot added this to the 1.132.0 milestone Jul 29, 2026

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Dmitriy Vasyura (dmitrivMS) commented Jun 11, 2026

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Peter Wan (peterdanwan) commented Jun 12, 2026

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Peter Wan (peterdanwan) commented Jun 11, 2026 •

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