[epic] enable Rust compiler for OSS

[kassens]

This issue collects what I think is missing to update the Relay compiler to the Rust version in OSS. If someone want's to give any of this a shot, please comment here!

• Typescript generator as something configured in the compiler config.json
• Non-watchman file source. Currently we convert the directories in config.json into a watchman query for watch mode and simple builds. This was designed with non-watchman in mind and it should be possible to build out something that uses a different file-crawler and maybe file watcher crate. This is not strictly required, but I think removing this external required dependency would be nice. (Details in [rust] add non-Watchman file source #3193)
• Figure out how we deploy a pre-build binary using npm. The flow-bin package might be a good inspiration as that somehow loads the binary for that version on first use. (Details/discussion in [rust] figure out how to deploy pre-built binary to npm #3194)
• Some missing config options in how types are generated (Details/discussion in [rust] missing flow typegen config options #3195)
• Refine Typescript generation (Details/discussion in [rust] refine typescript type generation #3196)
• Rust compiler: purging non-Relay files from __generated__ folders #3438
• Rust compiler: definition of 'XYZQuery' appears to have changed #3437
• Look at assumptions of using hg
• Figure out situation with required variables with default values (see: [fix] experimental compiler: allow default args on required fields #3612 )
• Documentation/Blog Post about the release of new version of the compiler
• Deprecate JS version of the compiler
• [Rust][Compiler] Add Configuration/Document Query Persisting in the OSS Compiler #3627
• Fix issues listed here: https://github.com/vincentriemer/new-relay-compiler-issues-repro

[kassens]

@MaartenStaa made a huge leap start on this with #3182!

I understand there's a few improvements we can make to the types still by copying more what the JS OSS typescript generator produces: https://github.com/relay-tools/relay-compiler-language-typescript/blob/e1b092f081d4e816ecd17fb0d3b4e62cdf3db917/test/__snapshots__/TypeScriptGenerator-test.ts.snap

I'll file separate issues for the remaining checkboxes.

[kassens]

A good intro way to contribute is #3199 to convert the runtime unit tests to use artifacts generated by the Rust compiler. More details in there.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[alunyov]

Thanks stale-bot. I think we still need the issue. I'm looking at converting the rest of the tests. It may take a while, but we'll see.

[alunyov]

Non-watchman file source. Currently we convert the directories in config.json into a watchman query for watch mode and simple builds. This was designed with non-watchman in mind and it should be possible to build out something that uses a different file-crawler and maybe file watcher crate. This is not strictly required, but I think removing this external required dependency would be nice. (Details in #3193)

One more point on why we may need to work on this: the current watchman client for rust doesn't work on Windows (I was testing it with github actions for windows: https://github.com/alunyov/relay/runs/2104656440?check_suite_focus=true). So we may add something like: https://github.com/notify-rs/notify in OSS.

[kassens]

Baby steps, the example project todo app now compiles with the rust based compiler:

relayjs/relay-examples@470c497

NOTE: this is currently linux + mac only and requires watchman. Windows support is definitely a hard blocker for us, this is just an early preview to see where the problems are.