Document how to create the spring binstub

[lakim]

Hey there,

Thanks for the great tool.
I wanted to speedup standardrb, especially when running in VS Code for linting and to format on save (needs rubyide/vscode-ruby#548).

I created spring-commands-standard to configure spring to generate the bin/standardrb binstub.

Example on a 13 lines file:

# Before
$ time bundle exec standardrb --fix path/to/file.rb
bundle exec standardrb --fix   1,33s user 0,35s system 102% cpu 1,650 total

# After
$ time bin/standardrb --fix path/to/file.rb
Running via Spring preloader in process 32323
bin/standardrb --fix   0,35s user 0,15s system 68% cpu 0,723 total

See the PR to update spring's README: rails/spring#612

[searls]

Cool!

Rubocop has some pretty sophisticated caching built-in (which standard benefits from for free), so that leads me to ask how does this performance improvement compare if you just run the same standard command twice (where the second invocation should be much faster) before calling it with Spring?

[lakim]

Here's what I have:

$ spring stop
Spring stopped.

$ time bin/standardrb --fix path/to/file.rb
Running via Spring preloader in process 27904
bin/standardrb --fix   0,30s user 0,13s system 13% cpu 3,269 total

$ time bin/standardrb --fix path/to/file.rb
Running via Spring preloader in process 28086
bin/standardrb --fix   0,29s user 0,10s system 59% cpu 0,660 total

So the first binstub call is pretty expensive (around 2x more than a regular bundle exec standardrb.
But subsequent calls are roughly 2x faster than bundle exec standardrb.
No real benchmark here, but a few runs on my machine on a small file.

[searls]

I can't tell from what you've posted if this benefit is due to rubocop caching or not, but I'm happy to link to your resource anyway if you think it's helping

[lakim]

Great, thanks!