TypeScript 3.9 Iteration Plan

Created on 4 Mar 2020 · 28Comments · Source: microsoft/TypeScript

This document outlines our focused tasks for TypeScript 3.9, as well as some of the discussion that explains how/why we prioritized certain work items. Nothing is set in stone, but we will strive to complete them in a reasonable timeframe.

Date | Event
--------------|------------------------
February 20th | TypeScript 3.8 Release (past)
March 20th | Create 3.9 Beta (3.9.0) Build for Testing
March 24th | TypeScript 3.9 Beta Release
April 24th | Create 3.9 RC (3.9.1) Build for Testing
April 28th | TypeScript 3.9 RC Release
May 8th | Create 3.9 Final (3.9.2) Build for Testing
May 12th | TypeScript 3.9 Final Release 🚀

Work Items

Expected Work Items

Stability
- Eliminate crashes
  - Address compiler-bound crashes first, typically impact the LS too.
  - Assign priorities to crashes from telemetry and fuzzing
  - Compiler team addresses work items
- Investigate better TSServer logging for easier issue reports
Performance
- Investigative
  - Work with users
- Improve build times for popular libraries
  - Giant unions (MUI and styled-components)
- Update Perf Suite
  - Current Compiler
  - Code using popular libraries
- Parallelized --build mode for project references
- Lazy-loading projects in preview tabs
Infrastructure
- Moving to modules
  - Helps us catch module issues sooner
  - Eventually can be the basis of solving package size issues
- Pull Request Debt
- Automate more release activities
Compiler work
Editor Productivity and Language Service
- VS Code Priority bugs
- Investigate Discoverability for Refactorings/Quick Fixes
- Switch ATA to GitHub Package Registry
  - Tentative: blocked on un-authenticated downloads
Command Line Tooling
- downlevel-dts
  - Move to Microsoft organization
  - Set out policies/contribution guidelines
  - Provide documentation and workflow guidance
Documentation

Planning

Source

DanielRosenwasser

👍61 ❤23 🚀22

Most helpful comment

https://github.com/microsoft/TypeScript/pull/35392

https://github.com/microsoft/TypeScript/issues/20469

This issue has not been resolved for a long time since the question was asked.

Support JSX fragments with jsxFragFactory compiler option and @jsxFrag pragma

masx200 on 8 Mar 2020

👍7

All 28 comments

Thanks

LittleStoney on 5 Mar 2020

The current awaited type operator PR is https://github.com/microsoft/TypeScript/pull/35998.

ExE-Boss on 5 Mar 2020

🎉3 👍1

https://github.com/microsoft/TypeScript/pull/35392

https://github.com/microsoft/TypeScript/issues/20469

This issue has not been resolved for a long time since the question was asked.

Support JSX fragments with jsxFragFactory compiler option and @jsxFrag pragma

masx200 on 8 Mar 2020

👍7

Is it possible to support mjs/cjs in ts 3.10?

xiaoxiangmoe on 10 Mar 2020

@xiaoxiangmoe does https://github.com/microsoft/TypeScript/pull/35148 satisfy it? 🤔

Jack-Works on 10 Mar 2020

👍2

@typescript-bot create release-3.9

DanielRosenwasser on 21 Mar 2020

🚀2

Heya @DanielRosenwasser, I've started to create the release-3.9 branch for you. Here's the link to my best guess at the log.

typescript-bot on 21 Mar 2020

https://github.com/microsoft/TypeScript/pull/37510 should probably be merged too.

It’s the only part of https://github.com/microsoft/TypeScript/pull/36368 that wasn’t included in https://github.com/microsoft/TypeScript/pull/35998.

ExE-Boss on 21 Mar 2020

For those following the issue and the listed features, we noticed that a lot of code was being impacted by awaited and we've decided that we need to back out the feature to ensure that we can roll it out more smoothly later on. Had we caught some of the errors sooner (see #37560), we might've gotten a better hint around some more of the impact, but even then we've just hit more stuff doing offhand experiments with public repos. Since the PR, we've seen

And we still have some fixes to awaited in flight:

We considered keeping awaited in and pulling it back out if the issues seem insurmountable, but this seems like an unfair amount of churn to impose on users, especially since the fixes aren't necessarily backwards-compatible. Asking users to use awaited and then remove it if we think it's not working out would be a waste of time for everyone.

We also considered pushing back the beta another week. Adding delays for a feature isn't something we want to start doing, especially because "fixing" a feature takes an indefinite amount of time with enough unknown unknowns. In the worst-case scenario, a bunch of fixes followed by a total rollback of a feature would delay our releases even further.

So the course of action we're taking is:

Delay the beta by another day or two.
Back out the changes and run a bunch of tests to ensure nothing else regresses (including another round of validation on the Visual Studio side just to be safe).
Revisit the awaited type for a later version.

I think this is the most ideal outcome. By not rushing this feature, we'll have a much better handle on it and its impact. 3.9 beta won't be delayed any further, and we'll still have a reasonable amount of time for feedback before the RC for other features.

DanielRosenwasser on 26 Mar 2020

👍3 ❤1

I think that 4.0 might be a better version for awaited, given that it has backwards compatibility issues.

ExE-Boss on 26 Mar 2020

👍1

I think it's reasonable to request people to change the T to awaited T. TypeScript is inferring it correctly

Jack-Works on 26 Mar 2020

👍1

Type system shouldn't implicitly create awaited types by default. Creating awaited types by Promise functions and methods and async/await operators obviously breaks existing code. So you should provide the stricter type inference and the lib.d.ts using awaited operator only when a flag is enabled.

// strictAwaitedTypes: false
// lib.es5.d.ts
  then((value: T) => awaited T | T): Promise<T>;
// strictAwaitedTypes: true
// lib.es5.awaited.d.ts
  then((value: awaited T) =>  awaited T | T): Promise<awaited T>;

// strictAwaitedTypes: false
await value; // Returns T
// strictAwaitedTypes: true
await value; // Returns awaited T

falsandtru on 27 Mar 2020

@typescript-bot sync release-3.9

DanielRosenwasser on 25 Apr 2020

Heya @DanielRosenwasser, I've started to sync release-3.9 with master for you. Here's the link to my best guess at the log.

typescript-bot on 25 Apr 2020

Had to do it manually. 😢 Ah well.

@typescript-bot bump release-3.9

DanielRosenwasser on 25 Apr 2020

Heya @DanielRosenwasser, I've started to update the version number on release-3.9 to 3.9.1-rc for you. Here's the link to my best guess at the log.

typescript-bot on 25 Apr 2020

🚀1