📎 Split up xtask into smaller crates

[Boshen]

Description

The xtask crate is getting bloated. This has the side effect of:

• super slow compilation speed when running xtask commands, since compilation is cached by unit of crates, splitting it up will improve both local and CI build time.
• our codegen scripts fail if any crate that the parser depends on has a syntax error. This is particularly annoying if there are merge conflicts in generated files

---

Rust Compilation speed needs to be engineered, development experience can suffer if we are not careful. We can use cargo bloat to watch out for outliers.

On my 2015 mac book, Running cargo bloat --time -j 1 gives

102.37s lsp_types
 75.87s rslint_parser
 73.65s clap
 72.18s rome_lsp
 42.39s criterion
 40.82s lspower
 36.47s futures_util
 31.71s tokio
 29.53s clap_derive
 29.31s rayon
 28.81s xtask
 27.40s serde_derive
 26.97s schemars
 25.64s syn
 23.27s syn
 20.24s rustls
 20.03s clap
 ... more omitted

xtask and its dependencies are all sitting on the top.

[ematipico]

How would you suggest to split them up?

[Boshen]

Along the lines of

xtask/
  cli/
  codegen/
  syntax/
  format/
  compare/
  coverage

+ Some command aliasing in .cargo/config.toml

[ematipico]

If we decided to move each command in its own crate, I don't think it would make sense to have a CLI. I mean, the CLI is what glues all together, resulting on a bloat.

I think we can just create cargo aliases and call it a day? And we could prefix those aliases with cargo dev?

[Boshen]

I'll experiment on this once all the other PRs are merged in (rust 1.58.0, whitespace, unicode codegen).

[Boshen]

I'm going to start working on this. I'm currently waiting forever for everything to compile in xtask 😢

[ematipico]

Would you mind opening issue first? And explain how you plan to implement the solution? I believe there's room for multiple "good first issue" once we know how to move each command.

[Boshen]

I'm almost done moving them 😄 It's easier to untangle everything in one piece. I'll create a Draft PR soon.