Fix Vertical Whitespace Rule performance issue and make it not opt-in

[dcaunt]

Swiftlint 0.11.2 hangs on my project (while 0.11.1 does not) when linting a file. I've pared down the file as much as possible to make it easier to identify the bug. I couldn't see a way to run swiftlint in a verbose mode to debug further.

// AppDelegate.swift


import Foundation
import SuperDelegate
import Fabric
import Crashlytics
import WebImage
import FBSDKMessengerShareKit
import FBSDKCoreKit

@UIApplicationMain
class AppDelegate: SuperDelegate, ApplicationLaunched, CrashStatusStorage {

    var dependencies: AppDependencies!

    func setupApplication() {
        // Required for SDWebImage to follow 302 redirects
        SDWebImageDownloader.sharedDownloader().setValue("text/html,image/*;q=0.8", forHTTPHeaderField: "Accept")
    }

    func loadInterfaceWithLaunchItem(launchItem: LaunchItem) {
        FBSDKApplicationDelegate.sharedInstance().application(UIApplication.sharedApplication(), didFinishLaunchingWithOptions: launchItem.launchOptions)

        dependencies.installRootViewControllerIntoWindow(window)

        switch launchItem {
        case let .OpenURLItem(urlToOpen):
            break

        case let .UserActivityItem(userActivity):
            continueUserActivity(userActivity, restorationHandler: { (_) in
                // Nothing to do here.
            })

        case let .RemoteNotificationItem(remoteNotification):
            break
        case .NoItem:
            // We were launched from Springboard or the App Switcher.
            break
        default:
            break
        }
    }
}

[jpsim]

Looks like a performance regression in 0.11.2. Thanks for reporting this.

Note that SwiftLint 0.11.2 does complete when linting your file, it just takes much longer than it should.

This is why having performance benchmarks/tests would be immensely useful (#376).

---

I couldn't see a way to run swiftlint in a verbose mode to debug further.

swiftlint lint --benchmark will output 2 files: benchmark_files.txt and benchmark_rules.txt that breaks down how much time was spent in each file and in each rule, respectively.

It turns out that the vertical whitespace rule is the culprit:

0.000: file_length
0.000: leading_whitespace
0.000: trailing_whitespace
0.000: custom_rules
0.000: type_body_length
0.000: closing_brace
0.000: todo
0.000: force_try
0.000: statement_position
0.000: legacy_constant
0.000: legacy_constructor
0.000: private_unit_test
0.000: function_parameter_count
0.000: legacy_cggeometry_functions
0.000: return_arrow_whitespace
0.000: operator_whitespace
0.000: force_cast
0.000: function_body_length
0.000: trailing_semicolon
0.000: variable_name
0.000: line_length
0.000: cyclomatic_complexity
0.000: control_statement
0.000: valid_docs
0.000: nesting
0.000: mark
0.000: trailing_newline
0.000: legacy_nsgeometry_functions
0.000: opening_brace
0.001: type_name
0.001: comma
0.001: colon
66.121: vertical_whitespace

---

Also, since SwiftLint is an Xcode project, you can easily run it with Instruments and/or debug it with LLDB to identify issues.

[jpsim]

Fixed in f559abb. Cutting 0.12.0 now to push this out to everyone asap.

[jpsim]

I'll reopen this to track fixing the actual performance issue and no longer making the rule opt-in.

[jpsim]

@masters3d do you think you could address this?

[masters3d]

I'll take a look

[masters3d]

I'll submit a PR momentarily.
/* in the file is tripping the regex to match multiline comments :(

SDWebImageDownloader.sharedDownloader().setValue("text/html,image/*;q=0.8", forHTTPHeaderField: "Accept")

let matchMultilineComments = "/\\*(.|[\\r\\n])*?\\*/"