Preserve inferred project ATA state by jakebailey · Pull Request #64327 · microsoft/TypeScript

Jake Bailey (jakebailey) · 2026-09-18T23:30:56Z

I noticed in our scripts dir (no tsconfig), that clicking on a file flashed errors. I closed it, opened another file, and the errors appeared and disappeared again! If I opened another file without closing the first, that one was fine.

The issue is that we lose the ATA state when inferred projects go away, so reopening causes ATA to happen again.

Save the state and apply it directly to inferred projects if present.

Copilot

Copilot review overview

🟡 Changes recommended

Cached ATA state can be incorrectly reused across unrelated roots or changed manifests.

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Review effort: Balanced
Findings: 1

Open (1)

Prevent stale ATA state reuse across roots and manifests · New

What changed in this PR

Preserves ATA results when inferred projects are recreated.

Changes:

Stores and restores inferred-project typings state.
Adds a reopening regression test.

File	Description
`projectcollectionbuilder.go`	Transfers cached ATA state.
`projectcollection.go`	Stores cached ATA state.
`project.go`	Defines ATA state capture/application.
`ata/ata_test.go`	Tests immediate typings restoration.

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Copilot

Copilot review overview

🟡 Changes recommended

Cache validation misses filesystem invalidation and changed ATA inputs, and content-mapped roots use incompatible hashes.

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Review effort: Balanced
Findings: 3

Open (3)

Validate compatible hashes for content-mapped ATA cache reuse · New
Clear cached ATA state when InvalidateAll has no changes · New
Prevent stale ATA state reuse across roots and manifests

Previously missed (1)

In code that hasn't changed since last review

Invalidate ATA cache when inferred-project options change

tsc/internal/project/project.go:214

Root names and contents are not the complete ATA input. If inferred-project compiler options change while no inferred project exists, the cached state is left untouched; reopening the same roots applies typings computed under the old options before ATA is queued in the background (and resolution-affecting options can also change the unresolved-import set). Preserve and compare the relevant command-line/mapping inputs, or invalidate this cache when those inputs change.

Copilot

Copilot review overview

🟡 Changes recommended

Stale ATA results can still overwrite invalidated configured or synthetic project state, and key new branches lack regression coverage.

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Review effort: Balanced
Findings: 1 · 2

Open (3)

Guard stale ATA results after all project invalidations · New
Test omission of unrelated cached typings · New
Add coverage for no-active-project retention results · New

Resolved since last review (3)

Clear cached ATA state when InvalidateAll has no changes
Validate compatible hashes for content-mapped ATA cache reuse
Prevent stale ATA state reuse across roots and manifests

 		logger.Embed(ataChange.Logs)
 		if _, ok := projectID.Inferred(); ok {
-			updateProject(b.inferredProject, ataChange)
+			if ataChange.SnapshotID < b.inferredProjectATAInvalidationSnapshotID {


 	packageNameToTypingLocation.Range(func(name string, typing *CachedTyping) bool {
 		registryEntry := typesRegistry[name]
-		if inferredTypings[name] == "" && registryEntry != nil && isTypingUpToDate(typing, registryEntry) {
+		if inferred, ok := inferredTypings[name]; ok && inferred == "" && registryEntry != nil && isTypingUpToDate(typing, registryEntry) {


+			}
+			if b.inferredProject.Value() != nil {
+				updateProject(b.inferredProject, ataChange)
+			} else {


Copilot

Copilot review overview

🟡 Changes recommended

The invalidation tombstone map grows indefinitely and adds increasing cloning cost to every snapshot.

Get a fresh assessment by requesting another Copilot review.

Review effort: Balanced
Findings: 1 · 1 · 2

Open (4)

Guard stale ATA results after all project invalidations
Unbounded tombstone map causes memory and snapshot-copy growth · New
Add coverage for no-active-project retention results
Test omission of unrelated cached typings

Copilot

Copilot review overview

🟡 Changes recommended

Unbuilt inferred-project transitions can discard valid cached results or temporarily unregister their watches.

Get a fresh assessment by requesting another Copilot review.

Review effort: Balanced
Findings: 1 · 3 · 2

Open (6)

Guard stale ATA results after all project invalidations
Retain cached ATA watch until validation completes · New
Preserve cached ATA results for unbuilt inferred projects · New
Avoid clearing cached ATA state from unbuilt projects · New
Add coverage for no-active-project retention results
Test omission of unrelated cached typings

Resolved since last review (1)

Unbounded tombstone map causes memory and snapshot-copy growth

An inferred project can exist without a program while cached ATA state is still authoritative. Keep that state and its watcher until a built program validates it, and reject results older than the latest installed or confirmed state.

Copilot

Copilot review overview

🟡 Changes recommended

ATA results can invalidate themselves during concurrent watcher events, and some installed-typing changes bypass invalidation.

Get a fresh assessment by requesting another Copilot review.

Review effort: Balanced
Findings: 1 · 2 · 2

Open (5)

Guard stale ATA results after all project invalidations
Empty FilesToWatch skips watching installed typings files · New
ATA install result is invalidated by its own coalesced file events · New
Add coverage for no-active-project retention results
Test omission of unrelated cached typings

Resolved since last review (3)

Avoid clearing cached ATA state from unbuilt projects
Preserve cached ATA results for unbuilt inferred projects
Retain cached ATA watch until validation completes

+	if len(filesToWatch) == 0 {
+		return false
+	}


+		if fileChangeSummaryAffectsTypingsWatch(
+			fileChanges,
+			slices.Concat(ataChange.TypingsFilesToWatch, ataChange.FileNames),
+			ataChange.TypingsFiles,
+			b.sessionOptions.TypingsLocation,


Typings cache writes are outputs of acquisition, not discovery changes, and can arrive in the same flush as their result. Keep those events available to the program while excluding them from ATA invalidation, without losing real package-owned inputs or full invalidations.

Jake Bailey (jakebailey) requested a balanced review from Copilot September 18, 2026 23:30

typescript-automation Bot assigned Jake Bailey (jakebailey) Sep 18, 2026

github-project-automation Bot added this to PR Backlog Sep 18, 2026

typescript-automation Bot added Author: Team For Uncommitted Bug PR for untriaged, rejected, closed or missing bug labels Sep 18, 2026

github-project-automation Bot moved this to Not started in PR Backlog Sep 18, 2026

Copilot started reviewing on behalf of Jake Bailey (jakebailey) September 18, 2026 23:31 View session

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Comment thread tsc/internal/project/projectcollectionbuilder.go Outdated

Jake Bailey (jakebailey) requested a balanced review from Copilot September 19, 2026 02:06

Copilot started reviewing on behalf of Jake Bailey (jakebailey) September 19, 2026 02:07 View session

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Comment thread tsc/internal/project/project.go Outdated

Comment thread tsc/internal/project/projectcollectionbuilder.go Outdated

Jake Bailey (jakebailey) marked this pull request as draft September 19, 2026 03:54

Jake Bailey (jakebailey) requested a balanced review from Copilot September 19, 2026 04:55

Copilot started reviewing on behalf of Jake Bailey (jakebailey) September 19, 2026 04:56 View session

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Jake Bailey (jakebailey) requested a balanced review from Copilot September 24, 2026 07:14

Copilot started reviewing on behalf of Jake Bailey (jakebailey) September 24, 2026 07:15 View session

Copilot AI reviewed Sep 24, 2026

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Comment thread tsc/internal/project/projectcollectionbuilder.go Outdated

Jake Bailey (jakebailey) force-pushed the preserve-inferred-ata branch from 9c3dbc0 to f0ea3e0 Compare September 24, 2026 12:39

Jake Bailey (jakebailey) added 3 commits September 24, 2026 08:12

Restrict cached typings to inferred packages

2545864

Preserve ATA state across project lifecycles

1df4257

test: Cover inferred project ATA reuse

49c879d

Jake Bailey (jakebailey) force-pushed the preserve-inferred-ata branch from f0ea3e0 to 49c879d Compare September 24, 2026 15:26

Jake Bailey (jakebailey) requested a balanced review from Copilot September 24, 2026 18:14

Copilot started reviewing on behalf of Jake Bailey (jakebailey) September 24, 2026 18:15 View session

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Comment thread tsc/internal/project/projectcollection.go Outdated

Comment thread tsc/internal/project/projectcollectionbuilder.go Outdated

Comment thread tsc/internal/project/projectcollectionbuilder.go Outdated

Handle unbuilt inferred projects during ATA

aef9b61

An inferred project can exist without a program while cached ATA state is still authoritative. Keep that state and its watcher until a built program validates it, and reject results older than the latest installed or confirmed state.

Jake Bailey (jakebailey) requested a balanced review from Copilot September 24, 2026 21:15

Copilot started reviewing on behalf of Jake Bailey (jakebailey) September 24, 2026 21:16 View session

Copilot AI reviewed Sep 24, 2026

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Preserve inferred project ATA state - #64327

Preserve inferred project ATA state#64327
Jake Bailey (jakebailey) wants to merge 5 commits into
microsoft:mainfrom
jakebailey:preserve-inferred-ata

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Jake Bailey (jakebailey) commented Sep 18, 2026

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