Rubocop: Add cop for block length

[aidalgol]

I would like a cop like Metrics/MethodLength but for blocks (as in do...end or {...}). I think this would be especially useful when using frameworks like Sinatra or Rake that heavily use methods with block parameters. (namespace, task, etc. in Rake; get, post, etc. with Sinatra.)

I am trying to implement this myself, but I'm getting a bit lost around AST-node pattern-matching.

RuboCop version

$ rubocop -V
0.43.0

[bbatsov]

You don't really need any pattern matching to write this. You just have to process on_block method invocations.

[aidalgol]

Awesome, thanks for implementing this! :grinning:

[sullerandras]

Is there an easy way to disable this cop for RSpec tests but keep it enabled for all other codes?

[bbatsov]

You can exclude your rspec tests dir from this cop's config. Or place a different .rubocop.yml in your rspec dir.