API `emit` support to generate .d.ts / .js files from sources by pfumagalli · Pull Request #3616 · microsoft/typescript-go

pfumagalli · 2026-04-27T00:27:57Z

Pull request overview

Adds initial end-to-end support for invoking the compiler’s emit through the TSGO API, wiring it through the Go API server and exposing it in the native-preview TypeScript client (sync + async), with virtual-FS write support to capture outputs.

Changes:

Added a new API method emit (protocol + session handler) that calls Program.Emit with EmitOnly and optional target source file.
Extended callback-based virtual filesystem support to include writeFile so emitted outputs can be captured by clients.
Added native-preview client API surface (program.emit), generated EmitFlags enum, and sync/async tests covering emit scenarios.

…um (GO)

(by Copilot) Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

…itter (by Copilot) Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

(by Copilot) Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

…re/emit-support

(by Copilot) Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

…Files`) as null (by Copilot)

(by Copilot) Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

pfumagalli · 2026-04-27T00:28:58Z

@microsoft-github-policy-service agree

Copilot

Pull request overview

Adds end-to-end support for invoking the compiler’s emit via the TSGO API, plumbing it through the Go API server and exposing it in the native-preview TypeScript client, including virtual-FS write support so emitted outputs can be captured by clients.

Changes:

Added a new API method emit (protocol + session handler) that calls Program.Emit with an EmitOnly mode and optional target source file.
Extended callback-based virtual filesystem support with a writeFile callback for capturing emitted outputs.
Exposed program.emit (sync + async) in native-preview, generated EmitFlags, and added sync/async tests for emit scenarios.

Reviewed changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
internal/compiler/emitter.go	Adds `EmitOnlyFromByte` validation helper for API inputs.
internal/api/session.go	Wires new `emit` method to snapshot/program resolution and `Program.Emit`, routing writes through session FS.
internal/api/proto.go	Adds `emit` method constant, request/response types, and `NewEmitResponse` adapter.
internal/api/callbackfs.go	Adds callbackFS support for delegating `WriteFile` to the client.
_packages/native-preview/src/api/fs.ts	Adds `writeFile` to the supported FS callback list and virtual FS implementation.
_packages/native-preview/src/api/sync/client.ts	Registers `writeFile` callback plumbing for sync transport.
_packages/native-preview/src/api/async/client.ts	Registers `writeFile` callback plumbing for async JSON-RPC transport.
_packages/native-preview/src/api/sync/types.ts	Introduces `EmitResult` type for sync API surface.
_packages/native-preview/src/api/async/types.ts	Introduces `EmitResult` type for async API surface.
_packages/native-preview/src/api/sync/api.ts	Exposes `EmitFlags`, exports `EmitResult`, and adds `Program.emit()` (sync).
_packages/native-preview/src/api/async/api.ts	Exposes `EmitFlags`, exports `EmitResult`, and adds `Program.emit()` (async).
_packages/native-preview/src/enums/emitFlags.ts	Adds generated runtime enum for emit mode selection.
_packages/native-preview/src/enums/emitFlags.enum.ts	Adds generated `const enum` variant for emit mode selection.
_packages/native-preview/test/sync/api.test.ts	Adds sync emit tests covering all/js/dts/single-file emit cases.
_packages/native-preview/test/async/api.test.ts	Adds async emit tests covering all/js/dts/single-file emit cases.
Herebyfile.mjs	Registers `EmitFlags` for enum generation from Go sources.

(by Copilot)

hegrec · 2026-05-11T06:29:13Z

Hey folks, any plans to merge this PR? This appears to be one of the missing links I've been hoping for. Specifically, the capability to wrap the emission pipeline with the virtual file system and serve virtual files to tsgo while subsequently capturing emissions (in my case, specifically interested in being able to capture d.ts content via writeFile on the JS side so I can store it in a custom location).

In my use case I am already leveraging the virtual file system to orchestrate the typechecking loop and this works really well. Would love to be able to have more or less the same approach with emit.

@jakebailey

As recommended by @jakebailey

Copilot

Pull request overview

Copilot reviewed 15 out of 15 changed files in this pull request and generated 1 comment.

Copilot

Copilot encountered an error and was unable to review this pull request. You can try again by re-requesting a review.

Copilot

Pull request overview

Copilot reviewed 15 out of 15 changed files in this pull request and generated 5 comments.

> Using a Go `byte`/`uint8` for a JSON field means invalid values > (negative, non-integer, >255) will fail during JSON unmarshal, > before `handleEmit` can wrap the error as `ErrClientError`. To > keep error handling consistent and provide clearer client errors, > consider unmarshalling `emitOnly` as an `int` (or `uint32`) and > doing explicit validation in `handleEmit`.

pfumagalli · 2026-07-06T11:50:15Z

Updated and resolved conflicts with upstream...

pfumagalli and others added 24 commits April 26, 2026 23:55

Enable the writeFile FS callback (GO)

a6b8f48

Protocol definition for the emit method (GO)

e468622

Validate and convert a byte value into members of the EmitOnly en…

0bc5cd9

…um (GO)

Implementation of the emit method (GO)

9649a4a

Generate EmitFlags

5936ba1

Generated enums for EmitFlags (TS)

5224065

Add writeFile to the callbacks to be registered (TS)

5784b15

Invoke emit in the TSGO server (WIP) (TS)

9de0ecf

Register the writeFile async callback (TS)

6b0461f

Register the writeFile sync callback (TS)

5af9c49

Align async->sync API (autogenerated, TS)

b7c2816

Fix targetSourceFile parameter and return result for tests (TS)

7565654

Test emit (TS)

306a8c8

Properly type the return value of emit (TS)

e118e2c

Export EmitFlags and EmitResult (TS)

c945828

Fix import of EmitFlags (TS)

d97f101

Fix targetSourceFile struct name

f085214

(by Copilot) Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Fix uppercase in Go error string

c140fad

(by Copilot) Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

WriteFile has an error return that can be propagated back to the em…

65733ec

…itter (by Copilot) Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Cleanup confusing local variable name

c03e4cc

(by Copilot) Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Merge remote-tracking branch 'origin/feature/emit-support' into featu…

5218d32

…re/emit-support

Fix for new name of TargetSourceFile in struct

8d2792f

(by Copilot) Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

NewEmitResponse can serialize diagnostics (and potentially `emitted…

b59f709

…Files`) as null (by Copilot)

Wrap error in ErrClientError

edebbd3

(by Copilot) Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Copilot AI review requested due to automatic review settings April 27, 2026 00:27

Copilot started reviewing on behalf of pfumagalli April 27, 2026 00:28 View session

Copilot AI reviewed Apr 27, 2026

View reviewed changes

Comment thread internal/api/session.go

Comment thread internal/api/proto.go

Guard against nil returned by program.Emit (GO)

3b80e8e

(by Copilot)

Merge branch 'main' into feature/emit-support

fc19a33

gantoine mentioned this pull request May 19, 2026

Track upstream TypeScript 7 (tsgo) APIs needed for kea-typegen migration PostHog/posthog#59093

Open

4 tasks

RyanCavanaugh added this to the Possible Improvement milestone May 20, 2026

Merge branch 'main' into feature/emit-support

7e9e512

jakebailey reviewed Jun 1, 2026

View reviewed changes

Comment thread internal/compiler/emitter.go Outdated

RyanCavanaugh added the No linked issue This PR doesn't say what bug it fixes label Jun 8, 2026

pfumagalli added 3 commits June 11, 2026 14:07

Merge changes from microsoft/main

a1352c1

Fix linting issues

1fc4ce5

Move EmitOnlyFromByte to api/session.go.

1d31e74

As recommended by @jakebailey

jakebailey requested a review from Copilot June 11, 2026 17:54

Copilot started reviewing on behalf of jakebailey June 11, 2026 17:55 View session

Copilot AI reviewed Jun 11, 2026

View reviewed changes

Comment thread internal/api/session.go Outdated

pfumagalli added 2 commits June 11, 2026 21:23

Merge branch 'main' into feature/emit-support

fef7fcb

Fix comment describing when the writeFile callback is not specified

58b8923

pfumagalli requested a review from Copilot June 11, 2026 19:57

Copilot AI reviewed Jun 11, 2026

pfumagalli requested a review from Copilot June 11, 2026 20:20

Copilot AI reviewed Jun 11, 2026

View reviewed changes

Comment thread internal/api/session.go Outdated

Comment thread internal/api/session.go

Comment thread internal/api/proto.go

Comment thread _packages/native-preview/src/api/sync/client.ts

Comment thread _packages/native-preview/src/api/async/client.ts

jakebailey requested review from andrewbranch and weswigham June 11, 2026 21:05

pfumagalli added 3 commits June 12, 2026 18:27

Merge upstream main

3569f2e

Merge branch 'main' into feature/emit-support

8d26111

Merge branch 'main' into feature/emit-support

cec5c32

jakebailey mentioned this pull request Jun 19, 2026

Add native-preview API for capturing .d.ts emit output #4375

Open

pfumagalli added 2 commits July 6, 2026 20:34

Merge microsoft:main and resolve conflicts

aec2a37

Fix project IDs after upstream changes

c027754

pfumagalli added 2 commits July 7, 2026 16:47

Merge branch 'main' into feature/emit-support

05af867

Merge branch 'main' into feature/emit-support

7dc0f62

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

API `emit` support to generate .d.ts / .js files from sources#3616

API `emit` support to generate .d.ts / .js files from sources#3616
pfumagalli wants to merge 41 commits into
microsoft:mainfrom
pfumagalli:feature/emit-support

pfumagalli commented Apr 27, 2026

Uh oh!

pfumagalli commented Apr 27, 2026

Uh oh!

Copilot AI left a comment

Uh oh!

Uh oh!

Uh oh!

hegrec commented May 11, 2026

Uh oh!

Uh oh!

Copilot AI left a comment

Uh oh!

Uh oh!

Copilot AI left a comment

Uh oh!

Copilot AI left a comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

pfumagalli commented Jul 6, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

5 participants

Uh oh!

Conversation

pfumagalli commented Apr 27, 2026

Pull request overview

Uh oh!

pfumagalli commented Apr 27, 2026

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Reviewed changes

Uh oh!

Uh oh!

Uh oh!

hegrec commented May 11, 2026

Uh oh!

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Uh oh!

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Uh oh!

Copilot AI left a comment

Choose a reason for hiding this comment

Pull request overview

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

pfumagalli commented Jul 6, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

5 participants