TypeScript 4.8 Iteration Plan

[DanielRosenwasser]

This document outlines our focused tasks for TypeScript 4.8. It minimally indicates intent to investigate tasks or contribute to an implementation. Nothing is set in stone, but we will strive to complete these tasks in a reasonable timeframe.

Date	Event
May 24th	TypeScript 4.7 Release
June 17th	Create 4.8 Beta (4.8.0) Build for Testing
June 21st	TypeScript 4.8 Beta Release
August 5th	Create 4.8 RC (4.8.1) Build for Testing
August 9th	TypeScript 4.8 RC Release
August 19th	Create 4.8 Final (4.8.2) Build for Testing
August 23th	TypeScript 4.8 Final Release 🚀

Language and Compiler Features

• ECMAScript Decorators
• Improved Inference for infer Types in Template String Types
• Investigate Contextually Typed And Compatible Operator
• Continue Investing in Type Annotations Proposal
• Investigate --isolatedDeclaration Emit Mode
• Improve Conformance for Arrow Functions in Conditional Expressions
• Investigate Narrowing Generics By Truthiness
• Investigate --watch Issues on Checkouts
• lib.d.ts Updates

Editor Productivity

• Prototype Virtual File System Support in TSServer
• Investigate Cancellation in Browser Contexts
• Prototype Automatic Type Acquisition in Web Contexts
• Provide Walkthroughs in Visual Studio Code Welcome View
• Easy Run/Debug for Loose TypeScript Files
• Investigate TS Server Plugins on the Web

Performance

• Investigate Tooling for JIT Deoptimizations
• Investigate Outstanding Performance Issues
• Enrich TS Server Tracepoint

Infrastructure

• Determining Module Migration and Shipping Strategy
• Fuzzer Improvements and Addressing Crashes
• TSServer Performance Testing Infrastructure
• Expand Perf Suite

Website

• Accessibility Improvements
• Investigate Playground as a VS Code Extension

[ghiscoding]

I wonder when will any of the opened issues related to Scenario: Monorepos & Cross-Project References will ever be worked and/or looked into? I'd be really interested to see this one in particular #30235, to build with multi-threads, and it's been open for so long without any real tractions. Are there any plans short term? When should we expect any movements in Monorepo subjects from TypeScript team? When will TypeScript ever take advantage of multi-threaded compilations? I'm sure plenty of users would enjoy the perf boost when doing a build... Anywho, I'm still happy to see plenty of features ship every couple months, keep up the good work TS Team 🚀

[JustFly1984]

Please include #17002 Array.isArray with ReadonlyArray

[Jack-Works]

please consider #49077!

[arendjr]

Please consider addressing #37582 and #49083.

[Eliav2]

#10571 (Allow skipping generics) would be highly appreciated

[DanielRosenwasser]

@ghiscoding the multithreaded build issue is something that is unfortunately hard with the synchronous foundation we have. There is also some amount of work sharing between project builds that we would likely lose. On the flip side, we did land some great optimizations between --build/--watch/--incremental in time for the beta. You can try them in our current nightlies.

[DanielRosenwasser]

@typescript-bot create release-4.8

[typescript-bot]

Heya @DanielRosenwasser, I've started to create the release-4.8 branch for you. Here's the link to my best guess at the log.

[kasperpeulen]

@DanielRosenwasser Is there any chance that the satisfies operator will land in 4.8?

[ostrowr]

@weswigham Looks like the beta release (https://github.com/microsoft/TypeScript/releases/tag/v4.8-beta) has a link to the 4.7 blog instead of the 4.8 blog. Excited for 4.8!

[DanielRosenwasser]

Fixed, thanks!

[dnalborczyk]

decorator support is being listed in v4.9 of the roadmap: https://github.com/microsoft/TypeScript/wiki/Roadmap#49-november-2022, as well as for v4.8 in this iteration plan issue. which is correct? I assume v4.9 as there was no mention of decorator support in the v4.8 beta release announcement: https://devblogs.microsoft.com/typescript/announcing-typescript-4-8-beta/.

[voxpelli]

Would love to get #49639 merged for TS 4.8 so that me and @ljharb can stop getting complaints about not following the spec in our polyfill a when it's actually TS that isn't.

[DanielRosenwasser]

@typescript-bot sync release-4.8

[typescript-bot]

Heya @DanielRosenwasser, I've started to sync release-4.8 with main for you. Here's the link to my best guess at the log.

[DanielRosenwasser]

@typescript-bot bump release-4.8

[typescript-bot]

Heya @DanielRosenwasser, I've started to update the version number on release-4.8 to 4.8.1-rc for you. Here's the link to my best guess at the log.

[crisbeto]

When is 4.8 final going to be released? The table above says that it was supposed to be on the 23rd.

[wegry]

@crisbeto for typescript 4.7, at least, the date planned for the final was ~5 days earlier than the final release date.

[DanielRosenwasser]

The plan changed for a release for today, in part due to the RC going out a little later.

[DanielRosenwasser]

@typescript-bot bump release-4.8

[typescript-bot]

Heya @DanielRosenwasser, I've started to update the version number on release-4.8 to 4.8.2 for you. Here's the link to my best guess at the log.

[DanielRosenwasser]

4.9 Iteration Plan is available at #50457

[andrewbranch]

@typescript-bot bump release-4.8

[typescript-bot]

Heya @andrewbranch, I've started to update the version number on release-4.8 to 4.8.3 for you. Here's the link to my best guess at the log.

[DanielRosenwasser]

@typescript-bot bump release-4.8

[typescript-bot]

Heya @DanielRosenwasser, I've started to update the version number on release-4.8 to 4.8.4 for you. Here's the link to my best guess at the log.

[jkowalleck]

the NPMJS 4.8.4 release was flagged 2 hours ago - https://www.npmjs.com/package/typescript/v/4.8.4 ,
but no git tag "v4.8.4" was pushed to github, and no github release was flagged. Without a git tag it is hard to review the delta to v4.8.3

@DanielRosenwasser was this indented behavior?

[DanielRosenwasser]

The GitHub release is pending. For the future, you can take a look at our milestones view.