Document Yarn Plug'n'Play

[arcanis]

We should document this to prepare for the 1.12 to move into stable.

• Short summary of what is Plug'n'Play
  • References the RFC PR (Yarn Plug'n'Play: Getting rid of node_modules rfcs#101)
• A page describing high-level effects
  • Getting started
  • Using plugins
  • References pnp-sample-app
• A page describing the Plug'n'Play interfaces
  • The API (require('pnpapi'), resolveToUnqualified, resolveQualified, resolveRequest)
  • The command line interface (+ "daemon" mode)
  • References build-pnm

[empyrical]

I noticed that you added custom resolver support to flow:

facebook/flow#6132

Does this help flow with PnP? If so, a mention on how to use Flow with PnP might be good too!

[arcanis]

Hey! Yes, Flow is supported out of the box - you just have to set the module.resolver option to your .pnp.js file (possibly using <PROJECT_ROOT> if you want) and you're good to go (note that you also need to make sure you're using the haste resolution).

[langri-sha]

@arcanis thanks for all the awesome work! Do you have a sample repository where Flow works?

I'm trying to setup a simple repository, but the Flow server seems to crash while starting up:

Dec 20 13:53:01.359 [info] argv=/home/filip/.cache/yarn/v4/npm-flow-bin-0.89.0-6bd29c2af7e0f429797f820662f33749105c32fa/node_modules/flow-bin/flow-linux64-v0.89.0/flow start --flowconfig-name .flowconfig --from parent cmdline: /home/filip/.config/yarn/global/node_modules/node-8/bin/node /home/filip/.cache/yarn/v4/npm-flow-bin-0.89.0-6bd29c2af7e0f429797f820662f33749105c32fa/node_modules/flow-bin/.bin/flow --temp-dir /tmp/flow /home/filip/work/yarn-pnp-flow-typed
Dec 20 13:53:01.359 [info] Creating a new Flow server
Dec 20 13:53:02.272 [error] Closing connection 'server #1' due to uncaught exception in read loop: End_of_file
Dec 20 13:53:02.272 [error] backtrace:
Dec 20 13:53:02.272 [error] Raised by primitive operation at file "src/unix/lwt_unix.cppo.ml", line 1549, characters 50-67
Dec 20 13:53:02.272 [error] Called from file "src/unix/lwt_unix.cppo.ml", line 563, characters 17-28
Dec 20 13:53:02.272 [error] 
Dec 20 13:53:02.287 [error] Flow server (pid 14374) exited with code Unknown_error (110)
Dec 20 13:53:02.288 [info] Monitor is exiting (Dying along with server)
Dec 20 13:53:02.288 [info] Broadcasting to threads and waiting 1 second for them to exit

[goodmind]

Have problems with flow too:

Cannot resolve module
/Users/goodmind/Library/Caches/yarn/v4/npm-react-16.7.0-b674ec396b0a5715873b350446f7ea0802ab6381/node_modules/react/index.js.

Flow version: 0.89.0
Yarn version: 1.12.3

# .flowconfig
[options]
module.system=haste
module.resolver=<PROJECT_ROOT>/.pnp.js

[arcanis]

Do you run flow through yarn flow? If so, I think this might be a side effect of yarnpkg/yarn#6629 - Node is bootstrapped with the hook preloaded (before process.mainModule is ready), and since Node never loads the same file twice it never gets executed in a context where process.mainModule is ready - meaning that it exits here instead of spawning the process.

I'll see to fix that; in the meantime, a simple workaround is to make a bash script as resolver, that contains something like this:

#!/usr/bin/env bash
NODE_OPTIONS='' node ./.pnp.js

This will prevent the resolver from being injected.

[goodmind]

@arcanis Unfortunately, still doesn't seem to work

[options]
module.system=haste
module.resolver=<PROJECT_ROOT>/pnp.sh

#!/usr/bin/env bash
NODE_OPTIONS='' node ./.pnp.js

Can this be related to workspaces?

[arcanis]

Nope, I don't think - is pnp.sh executable (chmod +x pnp.sh)?

[goodmind]

@arcanis yes -rwxr-xr-x

[arcanis]

Fixed by #907

[Billy-]

I notice the new documentation is now available at https://yarnpkg.com/en/docs/pnp (:tada:) and has a card/link on the docs homepage to it. But I can't get the "search documentation" box to return any results.

[arcanis]

I think it's just a matter of waiting for the Algolia cache to catch up, no worry ☺️

[Haroenv]

Yep, the docs are crawled every 24h