TypeScript 5.0 Iteration Plan

[DanielRosenwasser]

This document outlines our focused tasks for TypeScript 5.0. 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
November 15th	TypeScript 4.9 Release
January 20th	Create 5.0 Beta (5.0.0) Build for Testing
January 24th	TypeScript 5.0 Beta Release
February 24th	Create 5.0 RC (5.0.1) Build for Testing
February 28th	TypeScript 5.0 RC Release
March 10th	Create 5.0 Final (5.0.2) Build for Testing
March 16th	TypeScript 5.0 Final Release 🚀

gantt
    dateFormat  YYYY-MM-DD
    TypeScript 4.9 Stabilization Period : 2022-10-28, 2022-11-11
    TypeScript 5.0 Beta Development : 2022-10-28, 2023-01-19
    TypeScript 5.0 RC Development : 2023-01-19, 2023-02-24
    TypeScript 5.0 Stabilization Period : 2023-02-24, 2023-03-16
todayMarker stroke-width:5px,stroke:#0f0,opacity:0.5

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Language and Compiler Features

• ECMAScript Decorators
• Unify All enums as Unions
• Legacy Flag Deprecation
• Investigate Bundler-Oriented Module Resolution Options
• Support .ts as a Module Specifier for Bundler/Loader Scenarios
• Declaration Files for Non-JavaScript Files
• Allow Arrays in extends for tsconfig.json Files
• Investigate Per-File Settings
• lib.d.ts Updates
• Make @types/web Versionable

Editor Productivity

• switch/case Snippet Completions
• Investigate SharedArrayBuffer-Backed Host for Web Editing Contexts
• Investigate Limited ATA-Like Scenarios in Web Editing Contexts
• Implement Cancellation in Web Editing Contexts
• Easy Run/Debug for Loose TypeScript Files

Performance

• Investigate Module Resolution Caching in .tsbuildinfo Files
• Optimizing .tsbuildinfo
• Investigate Tooling for JIT Deoptimizations

Infrastructure

• Migrate TypeScript to Modules
• Enable strictFunctionTypes on TypeScript Codebase

Website

• Make Onboarding and Cross-Platform Installation Smoother

[DanielRosenwasser]

The 4.9 iteration plan is over at #50457.

[akononenko-sumo]

It's so sad that adding proper type support for throw is not on the roadmap for v5...

[MLoughry]

One idea I had previously floated to @amcasey was to add compiler/server APIs with asynchronous signatures in 5.0 (even if they're still synchronous under the hood), and deprecate the synchronous APIs. This would allow Typescript to later (6.0?) remove the synchronous APIs and unblock the ability to perform asynchronous I/O (or even worker-based parallelization?) in future versions.

[lukeapage]

I’d love to see the core team engage with issues that are for example 400+ thumbs up and marked “awaiting feedback” rather than issues that seem less important.
Even if the answer is that the team consider it to not be typescript’s responsibility and close the issue - i would rather that than limbo and newer but less important features being tackled.

https://github.com/microsoft/TypeScript/issues?q=is%3Aissue+is%3Aopen+sort%3Areactions-%2B1-desc+label%3A%22Awaiting+More+Feedback%22

[patroza]

@lukeapage I smell another 400+ thumbs up incoming..