tl;dr

• Is AppVeyor still used to test against Windows?
• Can it be moved to CircleCI?
• If not, can we update to use a modern version of node for it?

DeepDive into context and specifics

Currently the main CI testing seems to be done on CircleCI:

• https://github.com/facebook/react/blob/main/.circleci/config.yml

Yet there is also an AppVeyor config that appears to be used for testing against Windows:

• https://github.com/facebook/react/blob/main/appveyor.yml

Looking at the git history for appveyor.yml:

• https://github.com/facebook/react/commits/main/appveyor.yml

AppVeyor appears to have been added to run against the master (now main) branch in:

• [Question] Automatize tests on Windows environment && Circle CI 2.0 #11595
  • Migrate to CircleCI2.0 and Add AppVeyor for master-only branch #11605

It was updated to use NodeJS 10.x in:

• add nodejs 10 to windows test #13241

There was an attempt to move the Windows build from AppVeyor to CircleCI in #17984, but that was reverted in #18302 due to it slowing down the CI time:

• Move MS Windows build to CircleCI #17984

  • @wittgenst: Migrate the MS Windows continuous integration configuration from AppVeyor to CircleCI

  • Docs
    • https://circleci.com/docs/using-windows
    • https://circleci.com/developer/orbs/orb/circleci/windows
    • https://circleci.com/docs/hello-world-windows
• Revert "Move MS Windows build to CircleCI" #18302

  • @acdlite: I'm reverting this because it slowed our CI times from ~6 minutes to ~23 minutes. That's because it runs the build command without concurrency.

It was updated to run on the main branch when it was renamed from master:

• The primary branch has been renamed from "master" to "main" #21767
  • Updated scripts and config to replace "master" with "main" branch #21768

I stumbled across a few links to a publicly accessible AppVeyor project, but looking at the build output from that, it doesn't look like it's been built against for ~2 years:

• https://ci.appveyor.com/project/Facebook/react
• https://ci.appveyor.com/project/Facebook/react/history

I realise that there might be a different/non-public AppVeyor project that it is being built against now though.

If it's AppVeyor is still in use, and it's still not possible to migrate the Windows builds to CircleCI, it would be good to upgrade to a modern version of node:

• https://nodejs.org/en/about/releases/
  • node 14.x is the current Maintenance LTS
  • node 16.x is the current Active LTS

Looking at .circleci/config.yml, the jobs seem to run on the cimg/openjdk:17.0.0-node docker container:

• https://circleci.com/developer/images/image/cimg/openjdk
  • 17.0.0-node uses: node 14.17.6, yarn 1.22.5

Looking at .codesandbox/ci.json, it appears to use node 14.x.

• https://github.com/facebook/react/commits/main/.codesandbox/ci.json
  • Update Node.js to latest v14.17.6 LTS #22401
  • Update supported devEngines #21364

    • @eps1lon With node@12.16.0 yarn build react-server-dom-webpack/node-loader throws

  • Add CodeSandbox CI Config #17175

Looking at .nvmrc, it appears to use node 4.17.6:

• https://github.com/facebook/react/commits/main/.nvmrc
  • Update Node.js to latest v14.17.6 LTS #22401
  • fix: version in nvmrc #21430
  • Update nvmrc to the same one used in CI #18623
  • chore: Update nvmrc with latest lts #16610

Looking at package.json, devEngines is set to "node": "^12.17.0 || 13.x || 14.x || 15.x || 16.x || 17.x"

AppVeyor's Windows images include the following versions of node by default:

• https://www.appveyor.com/docs/windows-images-software/#node-js
  • 8.x is default Node.js installed on build workers
  • Node.js 16.8.0 (x86 and x64) - use Current alias for latest 16.x release
  • Node.js 15.0.0 - 15.14.0 (x86 and x64)
  • Node.js 14.17.6 (x86 and x64) - default on VS 2019 image. Use LTS alias for latest 14.x release
  • etc

So I think that either we should upgrade both AppVeyor and CircleCI to use a 16.x version of node, or at the very least, should upgrade AppVeyor to use the 14.x version (i'm unsure if there is any official list of node versions that React is intended to support being built on, but if so, then should probably test against all of those versions)

While this may not be too important currently (as presumably all of the build tools work at the moment), it will likely become more of an issue as time goes on, and the build tooling is upgraded to versions that will require newer versions of the node runtime:

eg. An improvement that would allow generating source maps for React would ideally be able to use a version of the magic-string library (which is used by a number of the Rollup plugins) that supports s.replace, but this version requires Node 12.x or higher, which currently would presumably break on AppVeyor as it uses node 10.x:

• Distribute source maps for easier debugging in Chrome's Performance tab #20186
  • Add source maps #21946 (comment)
• https://github.com/Rich-Harris/magic-string/blob/master/CHANGELOG.md#0260-2022-03-03
• https://github.com/rollup/plugins/search?q=magic-string&type=code

I found some previous PR's that attempted to make some of these sorts of changes, but they never seemed to land for various reasons:

• Test with AppVeyor with Node 11 and 12 #17197
  • This PR wanted to add node 11.x and 12.x alongside the existing 10.x in the AppVeyor testing matrix

  • @Saibamen Test with Node 11 and 12

  • @threepointone It usually works with later versions if it passes older versions, so I must ask: what specifically should be tested with newer versions? Is there something that breaks currently? Have you seen issues with other projects that could have been prevented by testing on newer versions? Happy to approve this if there’s a concrete reason.

  • @acdlite Can we replace AppVeyor with a CircleCI workflow instead? My understanding is that we only use AppVeyor because CircleCI used to not support Windows. But now it does: https://circleci.com/blog/windows-general-availability-announcement/

• Update Yarn to version Berry #24301
  • This PR attempts to upgrade to yarn 3.x, enables corepack, updates AppVeyor's node version to 16.x, etc

  • @tiziodcaio I upgraded to yarn v3.2.0, which would not work anymore on nodejs 10

  • @kachkaev Upgrading to Yarn 3 is blocked by the lack of Dependabot support: Support Yarn v2  dependabot/dependabot-core#1297