[api] Provide module resolution overrides by andrewbranch · Pull Request #64299 · microsoft/TypeScript

Andrew Branch (andrewbranch) · 2026-09-16T16:49:29Z

This needs some tests for snapshot/program updates after #64204 lands, so marking as draft for now. I'll write up more description when I undraft.

Fixes #64069

Add snapshot-scoped reusable module resolvers and serializable resolution overrides for standalone resolution and createProgram.\n\nCo-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

# Conflicts: # packages/typescript/src/api/async/api.ts # packages/typescript/src/api/proto.generated.ts # packages/typescript/src/api/sync/api.ts # packages/typescript/test/async/api.test.ts # packages/typescript/test/sync/api-generators.test.ts # packages/typescript/test/sync/api.test.ts # tools/gen-proto/main.go # tsc/internal/api/proto.go # tsc/internal/api/session.go # tsc/internal/project/refcountcache_test.go # tsc/internal/project/snapshot.go # tsc/internal/project/snapshothost.go

Cover reusable sets, changed and removed providers, repeated inline specs, and callbacks under the snapshot reconfiguration model.\n\nCo-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Exercise synthetic-program reconfiguration end to end for reusable sets, changed and removed providers, repeated inline specs, and callbacks.\n\nCo-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

🟡 Changes recommended

Public LSP integration, callback lifecycle, handle ownership, and resolution metadata have unresolved correctness issues.

Get a fresh assessment by requesting another Copilot review.

Pull request overview

Adds snapshot-scoped module resolution APIs and program-level resolution overrides.

Changes:

Adds reusable resolution sets, resolvers, callbacks, and fallback behavior.
Integrates overrides into compiler program creation and snapshot updates.
Exposes synchronous/asynchronous TypeScript APIs with tests.

File summaries

File	Description
`tsc/internal/project/snapshot.go`	Exposes snapshot resolution-host functionality.
`tsc/internal/project/projectcollectionbuilder.go`	Applies resolution providers to synthetic projects.
`tsc/internal/project/project.go`	Stores providers and passes them to programs.
`tsc/internal/module/types.go`	Defines the resolution-provider interface.
`tsc/internal/module/resolver.go`	Adds directory-based module resolution.
`tsc/internal/lsp/server.go`	Connects API sessions for callbacks.
`tsc/internal/compiler/program.go`	Tracks providers and resolution errors.
`tsc/internal/compiler/filesparser.go`	Propagates resolution errors.
`tsc/internal/compiler/fileloader.go`	Invokes resolution overrides while loading imports.
`tsc/internal/api/session.go`	Handles new module-resolution requests and providers.
`tsc/internal/api/session_module_resolution_test.go`	Tests resolution sets, callbacks, and programs.
`tsc/internal/api/session_createprogram_test.go`	Updates request-conversion tests.
`tsc/internal/api/server.go`	Initializes callback connectivity.
`tsc/internal/api/proto.go`	Defines module-resolution protocol messages.
`tsc/internal/api/module_resolution.go`	Implements API resolution behavior.
`tools/gen-proto/main.go`	Generates the resolution-mode API type.
`packages/typescript/test/sync/api.test.ts`	Tests synchronous provider reconfiguration.
`packages/typescript/test/sync/api-generators.test.ts`	Tests generator-method parity.
`packages/typescript/test/async/api.test.ts`	Tests asynchronous provider reconfiguration.
`packages/typescript/src/api/syncChannel.ts`	Supports callback unregistration.
`packages/typescript/src/api/sync/client.ts`	Registers synchronous callbacks.
`packages/typescript/src/api/sync/api.ts`	Exposes synchronous resolution APIs.
`packages/typescript/src/api/proto.generated.ts`	Adds generated protocol definitions.
`packages/typescript/src/api/async/client.ts`	Registers asynchronous callbacks.
`packages/typescript/src/api/async/api.ts`	Exposes asynchronous resolution APIs.

Review details

Suppressed comments (4)

packages/typescript/src/api/async/api.ts:265

A ModuleResolutionSet is scoped to the API session that created it, but this only checks disposal before serializing its numeric ID. If a set from another API instance is passed here, both sessions can have (for example) set ID 1, causing the request to silently use an unrelated resolution set. Validate that the set belongs to the current client/session before sending its ID.

    if (input instanceof ModuleResolutionSet) {
        input.ensureNotDisposed();
        return { set: input.id };

packages/typescript/src/api/sync/api.ts:282

A ModuleResolutionSet is scoped to the API session that created it, but this only checks disposal before serializing its numeric ID. If a set from another API instance is passed here, both sessions can have (for example) set ID 1, causing the request to silently use an unrelated resolution set. Validate that the set belongs to the current client/session before sending its ID.

    if (input instanceof ModuleResolutionSet) {
        input.ensureNotDisposed();
        return { set: input.id };

packages/typescript/src/api/async/api.ts:273

The disposer returned by client.registerCallback is discarded. Every snapshot creation/reconfiguration and module-resolver creation with a callback therefore leaves a handler that captures the user callback until the entire API connection closes, even after the owning snapshots are disposed. Track the disposer and unregister once no live snapshot or resolver can reference this callback.

    client.registerCallback(name, params => {

packages/typescript/src/api/sync/api.ts:290

The disposer returned by client.registerCallback is discarded. Every snapshot creation/reconfiguration and module-resolver creation with a callback therefore leaves a handler that captures the user callback until the entire API connection closes, even after the owning snapshots are disposed. Track the disposer and unregister once no live snapshot or resolver can reference this callback.

    client.registerCallback(name, params => {

Files reviewed: 25/25 changed files
Comments generated: 3
Review effort level: Balanced

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Copilot

🟡 Changes recommended

Callback errors, callback lifetimes, cross-client handles, and concurrent disposal remain incorrect.

Get a fresh assessment by requesting another Copilot review.

Review details

Suppressed comments (3)

Previously missed (3) — in code that hasn't changed since the last review.

packages/typescript/src/api/async/api.ts:268

This accepts a ModuleResolutionSet created by any API instance. Since set IDs are allocated per server session, passing a set from API A into API B can either report “not found” or, if B has allocated the same numeric ID, silently use B's unrelated resolutions. Validate that the set belongs to the current client before serializing its handle.
packages/typescript/src/api/async/api.ts:283
The disposer returned by client.registerCallback is discarded, so every callback supplied while creating or reconfiguring programs/resolvers remains registered and retains its closure until the whole connection closes. Repeated snapshot updates therefore grow the callback registry without bound, including when the API request fails. Track the disposer with the provider's owning snapshot/resolver and unregister it once no live snapshot can use that provider.
packages/typescript/src/api/async/api.ts:912
disposed is set only after the release request completes, so two concurrent calls to dispose() both send releaseModuleResolutionSet; the second request then fails because the server handle is already gone. Memoize the in-flight disposal promise, as Snapshot.dispose does, to keep disposal idempotent under concurrency.

Files reviewed: 25/25 changed files
Comments generated: 1
Review effort level: Balanced

 		changes = &LanguageServerSnapshotChanges{}
 	}
-	update, err := s.toLanguageServerSnapshotUpdate(&changes.SnapshotRequestChangesParams)
+	update, err := s.toLanguageServerSnapshotUpdate(ctx, &changes.SnapshotRequestChangesParams)


Andrew Branch (andrewbranch) and others added 4 commits September 15, 2026 08:44

[api] Add module resolution APIs

71d1d9c

Add snapshot-scoped reusable module resolvers and serializable resolution overrides for standalone resolution and createProgram.\n\nCo-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Format rebased module resolution changes

89bdab8

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Support module resolution overrides and programless resolveModuleName

c49318e

Add callback as a way of overriding too

cf4a7b7

typescript-automation Bot assigned Andrew Branch (andrewbranch) Sep 16, 2026

typescript-automation Bot added Author: Team For Uncommitted Bug PR for untriaged, rejected, closed or missing bug labels Sep 16, 2026

Andrew Branch (andrewbranch) added 5 commits September 17, 2026 16:00

Test module resolution state updates

5cfe713

Cover reusable sets, changed and removed providers, repeated inline specs, and callbacks under the snapshot reconfiguration model.\n\nCo-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Move module resolution state tests to API client

67b47d4

Exercise synthetic-program reconfiguration end to end for reusable sets, changed and removed providers, repeated inline specs, and callbacks.\n\nCo-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Merge remote-tracking branch 'upstream/main' into api-module-resolution

be9c56e

Format

314fd68

Andrew Branch (andrewbranch) requested a balanced review from Copilot September 18, 2026 15:34

Copilot started reviewing on behalf of Andrew Branch (andrewbranch) September 18, 2026 15:35 View session

Copilot AI reviewed Sep 18, 2026

View reviewed changes

Comment thread tsc/internal/api/module_resolution.go Outdated

Comment thread packages/typescript/src/api/async/api.ts

Comment thread packages/typescript/src/api/sync/api.ts

Fix snapshot params, add test for lack of resolvedUsingTsExtension

f91176d

Andrew Branch (andrewbranch) requested a balanced review from Copilot September 18, 2026 17:12

Copilot started reviewing on behalf of Andrew Branch (andrewbranch) September 18, 2026 17:13 View session

Copilot AI reviewed Sep 18, 2026

View reviewed changes

Comment thread tsc/internal/api/session.go

changes = &LanguageServerSnapshotChanges{}

}

update, err := s.toLanguageServerSnapshotUpdate(&changes.SnapshotRequestChangesParams)

update, err := s.toLanguageServerSnapshotUpdate(ctx, &changes.SnapshotRequestChangesParams)

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[api] Provide module resolution overrides - #64299

[api] Provide module resolution overrides#64299
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Andrew Branch (andrewbranch) commented Sep 16, 2026

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